Dripping overflow pipe: Overflow Pipe Leaking? How to fix it

Overflow Pipe Leaking? How to fix it

What is an Overflow Pipe?

An overflow pipe extends from the water storage tank to prevent water from leaking into the house area/rooms. The overflow pipe is the most important feature in your home’s plumbing system. Overflow Pipe Leaking happens when the tank or cistern fills up to a level more than it should, causing the excess water to flow down into the overflow pipe.

Some common components that have an overflow pipe in your home are:

  •   Toilet Cistern
  •   Cold water feed and expansion tank
  •   Central heating feed and expansion tank
  •   Copper cylinder
  •   Combination boiler
  •   Sinks, basins, and bathtubs

The toilet cistern, Cold water feed and expansion tank, Central heating feed and expansion tank, and the combination boilers overflow outside. The expansion pipe on the copper cylinder flows down into the cold water feed and expansion tank, and the one on the basin and bath flows into the draining sink.

Why is the Overflow Pipe Leaking?

One of the most common reasons that might cause overflow pipe leaking is a problem with a float valve. The float valve is a device that controls water level; it consists of a plastic/metal arm along with a plastic ball at the end of the arm that floats in the water. Float valves are found in toilet cisterns, expansion tanks, cold water tanks, and central heating feed.

This float valve keeps moving up and down along with the water level to switch on and switch off the cold water feed. The extent of the water level in the tank should be an inch below the overflow pipe. If the float valve does not operate correctly, the cold water feed may not be properly switched off, thus causing excess water overflow.

However, it is considered an alarming situation if the overflow pipe leaks- even if it’s a very small leak. Continuous water leaks might result in water overflow and you might have to switch off the entire plumbing system. Read below to find our simple step by step guide that will help you find where the leak is and what to do if you see the water leaking from an overflow pipe just so that you can quickly deal with the situation:

Identify Which Cistern/ Water Tank Is Overflowing

If the leaking pipe is seen on the ground or first floor, it might be your bathroom overflow pipe dripping and coming from the toilet cistern. But if it is at the loft level and is protruding out, then water might be coming from the expansion tank and the central heating feed.

Check the float valve & washer

Sometimes, if the water keeps continuously running into the tank, the float valve might get stuck. Check on the float valve, release it if it is seen stuck, and see if it repeats its normal function. Also, check on the ball to see if it’s punctured. If you find problems with the float valve and the ball, it needs to be replaced, and if everything is good, but still the water keeps leaking, then the washer might be worn out and needs to be replaced.

Turn Off Water Feed & Drain the Water

To work, first, you need to stop the flow of new water into the tank and drain it completely.

  •   Use the isolation valve to turn the water feed off on a toilet cistern.
  •   Use a flat head screwdriver to turn the screw clockwise and flush the toilet to drain the water.
  •   At the stopcock, turn off the mains to stop the water feeding into either of the water tanks.
  •   You could turn on your bathroom taps to drain it.
  •   See that the water level is below the area you need to work on.

Check water pressure

Leaky pipes are majorly the effect of increased water pressure. The tube may leak if the pressure exceeds the pipe’s pressure handling capacity. In addition, the water valve, which checks the pressure and the flow of water through the overflow pipe, might have loosened due to continuous water flow with increased pressure. Sometimes, the pipe might also face leakage due to damages.

Toilet Overflow Pipe Leaking

The toilet overflow pipe ends outside the house, and if the water flow within the tank or cistern doesn’t stop, it will overflow. This can be fixed in multiple ways:

  •   Check if the float valve is freely moving: There are chances that the float valve might be twisted within the valve chain.
  •   Regulate the float valve: Control the extent of the float valve by bending the arm or adjusting the screws to shut the water system off.
  •   Check water pressure: The overflow pipe may leak due to increased pressure in the water flow within the pipe. The water pressure can be checked in the isolation valve and must be closed to manage the flow.
  •   Replace the float valve or washer: There might be a damaged valve or washer if the water leakage does not stop after the remedial trials. If this is the case, the washer/ valve needs to be replaced.

Cold Water Feed and Expansion Tank Overflow Pipe Leaking

This cold water feed and expansion tank overflow pipe extend through the bigger water cistern to your house’s exterior. Water flows to the sinks from the tank. In the case of leakage in any of the system’s overflow pipes, it is because of the below reasons:

  •   The tank’s water inlet is not turning off.

If you find a constant drip of water inside the water feed tank, try to adjust/ replace the float valve or the washer.

  •   Water is being pressured back into the outlet pipe.

If the pipes, float valves, and washers seem to work fine, then the sole reason for the leakage is that the water is pushed back towards the leak through the outlet pipe. This issue could be solved by calling in a safe gas expert.

Call a Gas Safe Technician.

Central Heating Feed and Expansion Tank Overflow

 The central heating feed and expansion tank overflow pipe goes from your water tank in your loft to the outside of the house. Water to the central heating system of the house is provided by the feed and if the overflow pipe of the system is leaking, the two possible reasons are:

  •   The water feed going into the tank is not switching off

As soon as you see constant dripping of water into the tank, ensure that both the float valve is not damaged or worn out. If you find any such issues of damage, then go ahead and replace the float valve/ washer.

  •   A problem with your hot water cylinder

If you see your cold water feed working fine and your float valve and washer is also undamaged, then the only issue would be with your hot water cylinder.


Boiler Overflow Pipe Leaking

Boilers have a pipe consisting of a pressure relief valve similar to an overflow pipe. Under too much water pressure in the system, this valve releases water. Also, this pipe in the boiler has its end at the outside of your house and prevents any flooding. This valve only flows when there is a severe problem in the system, so if it is seen leaking, it is important to take notice of the issue immediately.

Note: Pressure Valve Pipes and Condense Pipes are two different. Hot water flows through the condensed pipes when the central heating system is turned on.

If your boiler is leaking water from an overflow pipe then there is excess pressure to the system or due to an issue in the pressure valve. In both cases, it is recommended to call in professionals.

Call a Boiler Repair Engineer

Overflow from Kitchen Sink

The overflow pipe of the sink is placed just below the sink and has its opening down the drain. This pipe stops your sink from overflowing. Hence, it would be difficult for you to point out if there is an issue with the sink overflow pipe. However, the problems and indications surface with your sinks or baths. But in case you spot any issue with the drain, then the simple solution is to unclog it and allow the sink to drain off.

Get a Plumbing and Drainage Cover

With all the above information, we have kept you covered with every issue that might happen with the water supply pipes and the why’s and how’s of it. Yet a blocked drain or a burst pipe will likely slow down anyone. So take out Smart Cover’s Plumbing and Drainage Coverto keep yourself up from unexpected situations.

At Smart Cover, we provide home emergency insurance coverage and for a vast range of home appliance products with a vision to be protective of our customer’s needs and emergency situation. In addition, we provide professional service, competitive premium rates and streamlined claims settlement processes.

Smart Cover’s plumbing & drainage insurance scheme includes:

  •   Emergencies related to the internal drainage system.
  •   Collapse/ Blockage/ Leak of the external water supply pipe.

Our engineers work around the clock on various household repair emergencies throughout the year. However, a plumbing and drainage breakdown can occur at any time, and we want you to be secure in knowing that you’re covered for repair costs. So reach out to Smart Cover’s plumbing & drainage insurance, and the solution is just a call away.

Why Is Water Dripping From My Overflow Pipe? (Fixed!!!)

It can be concerning if you’ve ever seen water dripping from your overflow pipe. You might wonder what’s wrong and whether or not you need to call a plumber.

In most cases, it’s usually not a big issue. However, it’s usually a sign that there’s a problem that needs to be solved. Keep reading to learn more about why water is dripping from my overflow pipe and what you can do to prevent it.

What is An Overflow Pipe?

An overflow pipe is a pipe that discharges excess water safely in order to prevent the water from overflowing inside the home.

These pipes can be found in all kinds of objects and structures used to hold or convey water, such as tanks. In addition to overflow prevention, overflow pipes also help lower the likelihood of a tank or channel holding too much water and collapsing from the pressure.

Overflow pipes are a form of the safety measure and, as such, only generally have water passing through at all times. Since water only passes through when the tanks reach the level of the overflow pipe, most overflow pipes only discharge drops of water, rather than discharging water in large volumes.

These cases indicate something is wrong with the line and should be addressed. For example, there might be leaks along the line or other problems causing water to run into the overflow pipe. Below are the possible reasons why water drips from an overflow pipe.

Toilet Cisterns

Toilet cisterns are present in almost all households. They have an overflow pipe to prevent the toilet from overflowing. In a properly functioning toilet, the water should be around an inch below the overflow pipe. To stop the water from reaching the overflow pipe, toilet cisterns have a float valve.

1. Water Pressure is Too High

The water level can increase drastically if the water pressure is too high. This increase in water can lead to the water reaching the overflow pipe. To prevent overflowing, the water pressure has to be adjusted.

If your water pressure is too high, it can cause problems throughout your home. Pipes can become clogged or burst, appliances can be damaged, and you may even see an increase in your water bill.

Fortunately, there are a few simple steps you can take to lower the water pressure in your home. First, check to see if there is a main shut-off valve. If so, turn it clockwise until the water pressure is reduced.

Next, check all of the fixtures in your home and see if they have individual shut-off valves. If so, turn these valves clockwise as well.

Finally, if you have a Pressure Reducing Valve (PRV), adjust it until the desired water pressure is reached. By following these steps, you can easily lower the water pressure in your home and avoid any potential problems, including overflowing.

2. Float Valve is Set Too High

The float valve can be adjusted to regulate the amount of water filling the cistern. In most cases, the float valve is set so that the cistern fills up about an inch below the overflow pipe.

However, incorrectly setting the float valve results in the cistern filling up above what is recommended, leading to water reaching the overflow pipe. In these cases, the float valve can be adjusted and set back to normal to prevent overflowing.

3. Float Valve is Not Working as Intended

As the name suggests, the float valve uses a floater to regulate water flow. However, impeding the floater’s movement can prevent the float valve from functioning correctly. In most cases, the chain becomes twisted, locking the floater in place.

This prevents the valve from closing, resulting in the cistern overflowing. Other forms of damage may also occur. In any case, the float valve should be repaired or replaced to stop the toilet cistern from overflowing.

Cold Water Feed and Expansion Tank

Cold water feed and expansion tanks store water for the heating system. These tanks are usually fed through a ball valve. The tank can be made from different materials, such as plastic or metal.

Water from the tank goes through heating systems and supplies water wherever necessary, such as through taps. These tanks also have overflow pipes to prevent overflowing, and below are some reasons why the overflow pipe of the cold water feed and expansion tank is letting water out.

1. The Water Supply Has Not Been Cut Off

A ball valve is usually used to regulate water flow into the tank. In most cases, the valve must be manually opened and closed to regulate the water flow.

There are cases, however, where the valve does not function correctly. For instance, a faulty valve may still allow water to flow into the tank despite being closed.

Some tanks use float valves to automatically regulate water flow into the tank without requiring much human intervention. However, like the ball valve, faulty float valves also do not cut off the water supply, increasing water volume inside the tank.

This results in overflowing if the water from the tank is not immediately fed to the heating systems. As such, the valves should be maintained well and repaired or replaced whenever damages are observed.

2. Water is Being Returned to the Tank

If the supply valves are working fine, but water is still coming out of the overflow pipe, then water is probably coming back into the tank. This usually happens when a faulty mixer fixture is used since hot and cold water both have different pressure.

What ends up happening is the pressure difference pushes water back into the tank, which can cause the tank to overfill. There are other possible causes, so it is best to call a plumber to repair the system and prevent water from reentering the tank.

Copper Cylinder

A copper cylinder is a vessel used to heat and store water. It is connected to the cold water feed and expansion tank and gives water room to expand when heated.

Copper cylinders are made of copper because of the material’s thermal properties. Below are the possible damages that the copper cylinder has sustained, causing it to leak water to the overflow pipe.

1. Temperature or Pressure is Too High

Copper is a good conductor of heat, allowing it to transfer heat more efficiently to the water inside. However, when the temperature gets too high, the pressure inside the cylinder also increases.

This leads to the vapor trying to escape the cylinder, which causes a leak. The temperature should not be too high to prevent the cylinder from getting too hot, thus effectively lowering the resulting pressure.

2. Perforations within the Copper Cylinder

Copper cylinders do not last forever. In fact, copper is quite susceptible to wear and tear. Perforations along the cylinder or pipes connected to the cylinder can cause leakage. The heating coil inside the copper cylinder is also susceptible to wear and tear and may have perforations.

Water can leak out from these perforations, resulting in the tank overflowing. In these cases, the only solution is to replace the copper cylinder.

Sink and Bath Overflow Pipe

Ever notice the tiny hole at the back of the sink, usually situated below the tap? That hole can often lead to the overflow pipe and is used to stop the water in the sink from overflowing. The same hole can be found in baths to prevent water from overflowing when the tap keeps running.

Problems with these fixtures are easily observed and can be easily solved. For instance, a clogged drain can be cleaned to allow the water to drain better. A faulty tap can also be repaired or replaced to stop water from flowing into the bath or sink, thus preventing an overflow.

Boiler Overflow Pipe

Boilers do not necessarily have overflow pipes to prevent the water from overflowing. Instead, boilers, similar to pressure cookers, have pressure relief valves. As the water boils, the pressure inside the container increases.

A pressure relief valve is attached to stop the boiler from breaking due to pressure. The pressure relief valve lets vapor out whenever the boiler pressure becomes too high. The pressure can be regulated by allowing the vapor to exit the boiler.

In cases where the pressure relief valve is releasing vapor non-stop, there is usually a problem. One such problem is that the boiler has too much pressure inside, possibly due to a faulty expansion valve.

A faulty pressure relief valve can also result in improper pressure release, resulting in improper water heating. Either way, the boiler needs to be assessed and repaired by an engineer before it becomes a bigger problem.

Final Thoughts

Overall, a leaking overflow pipe can come from various reasons, whether from a faulty toilet cistern to a faulty tank supply valve. Unfortunately, it is quite difficult to pinpoint the source of the leaks since the parts are connected.

To be able to determine the actual cause, each component of the line has to be checked. Therefore, professional help is always advised, especially when the problems involve the heating system.

Sometimes, however, the cause is obvious. For example, if your overflow pipe drips every time you flush your toilet, then it’s a great idea to check out the cistern. Hopefully, we’ve given you all the info you need to stop your overflow pipe from dripping.


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Drain in the bathroom is leaking: causes, methods of repair

A leak in the bathroom is possible anywhere where there are joints. The area where the siphon, sewer pipes and baths are connected is no exception. They don’t notice problems right away. Water droplets on a siphon are often considered ordinary condensate. If a puddle of water appears under the bath, it’s a leak.


  1. Leak Causes
  2. Leak Location
  3. Repair Tools and Materials
  4. Emergency leak repair
  5. Conventional repair methods
  6. Siphon repair
  7. Metal siphon and pipe repair

Causes of leaks

Water appears under the bath for a variety of reasons.

  • Connection of pipes and siphon is carried out using sealing rings – they guarantee the tightness of the joint and the density of the pressure. If one of the gaskets has stretched, cracked or simply lost elasticity , water starts to flow.
  • If overflow tube bursts, the puddle will be small at first. But the wider the crack in the tube, the greater the leakage.
  • If a leak appears almost immediately after the installation of the bathroom or after repair, the problem lies in poorly screwed and undertightened nuts .
  • Clogged siphon – Mud and hair plugs hold water. A constant pressure is created in the bend of the pipe, which sooner or later leads to a violation of the connections.
  • Defective gaskets – unequal thickness, poor quality material leads to leakage.
  • Loosening the joint between the drain and pipe allows water to escape to the surface of the siphon.
  • If pipes and partly threaded adapters were used during installation, the best quality gasket will not save the leak.
  • Less common, but cracks in the body of the siphon or even in the neck of the drain . A puddle of water appears very quickly.

It’s not just water on the floor that’s a sign of a leak. There is a leak if the surfaces of the siphon or pipe under the bowl are wet, a musty smell appears in the room.

Yes, it’s because of worn gaskets


Pipe burst / drain itself


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Finding a leak

If the siphon in the bathroom is leaking water , it is important to establish the cause of the breakdown. To do this, fill the bathroom with some amount of water, no more than half. If it’s the worn gaskets, they can handle the load with a small amount of fluid.

After draining the water , the following areas are inspected :

  • all threaded connections – not only the junction of the siphon and pipe, but also pipes, hoses, if they are threaded;
  • joints assembled on a gasket and sealed – if the sealant has crumbled, the joint looks uneven and half filled with moisture;
  • tapping points for all branches;
  • welding seams, if any, on sewers;
  • straight sections of the pipeline, if they are under high load.

The greatest danger is represented by pipes that divert water from different points of the consumer. When laying the sewer, the option is allowed when the plumbing is connected to the riser not separately, but in parallel. These areas are subject to maximum stress.

Repair Tools and Materials

The following tools and materials are required to fix a leak under a bathtub:

  • Adjustable wrench for dismantling metal pipes and siphon;
  • collar;
  • degreaser – acetone, white spirit;
  • sealant – epoxy adhesive, “cold welding”;
  • FUM tape or linen plumbing tow – the first option is easier to use;
  • liquid soap for lubrication;
  • bucket and cloths to collect liquid.
  • depending on the cause of the leak, you will need different elements to replace: rubber rings – it is better to choose the thickest ones;
  • new siphon, adapter, drain neck, etc.

If you need to replace an entire section of the pipeline, you will need a grinder for working on metal (if the pipeline is metal), couplings, fragments of the conduit 40-50 cm longer than the cut section.

Emergency Leak Repair

If the drain in the bathroom is leaking heavily at the junction, it is urgent to stop the leak. For this, various devices are used. The problem is only temporarily solved. In the future, you need to inspect the site and carry out major repairs.

  • Clamp or band is a metal ferrule used in pipeline assembly. If you supplement the product with a rubber gasket – a bandage, the design will help to urgently stop the leak. This method is suitable for breaking through small seams, but not cracks in the body. The rubber is wrapped around the leak, then a clamp is applied on top and tightened so that the damaged area is completely blocked. The clamp must match the diameter of the pipe. If there is no suitable one, you can tighten the gasket with an ordinary metal wire, instead of a bandage, use a piece of any dense rubber from a bicycle inner tube.
  • Leak can be repaired with self-tapping screw . This method is suitable for the formation of holes and cracks, the dimensions of which do not exceed 1–4 mm. The self-tapping screw allows you to eliminate leaks under pressure, that is, it is used when repairing water pipes, and not just sewer pipes. For repair, they take a galvanized self-tapping screw and a press washer. With a screwdriver or drill, the self-tapping screw is screwed into the place of leakage and tightly fixed. If the pressing washer is not enough, you can additionally seal the clamp with an elastic gasket. The method is temporary, since the self-tapping screw in the pipe is an obstacle on which dirt, grease, and debris successfully linger.
  • Cold Weld is an epoxy based compound. Includes hardener special additives that increase the strength of the connection. Used for pitting or corrosion in straight pipe runs. “Cold welding” is used only after turning off the water and completely drying the leak area. The place of a crack or parted joint must be cleaned with sandpaper, the paint is removed. Then a thick layer of glue is applied to the area. To speed up the setting time, you can heat the glue with a building hair dryer. When repairing plastic sewer pipes, a patch is used. It is planted on polyurethane glue or on “cold welding”.
  • Cementing – possible when the pipe can be completely drained and the area dry. You will need a cement mortar and a carrier – a bandage or strips of gauze. Prepare a thick solution as for finishing. It is recommended to add liquid glass to the mixture to increase water resistance. Then a second solution is prepared – saturated, but not pasty. A wide bandage is impregnated in it, cut into pieces of 25–30 cm each. Fragments of the bandage are wound around the damaged area. Each layer is coated with a thick cement mortar. You can turn on the water only after complete drying.

There are even faster methods. You can wrap the damaged pipe with a bandage, thickly sprinkling each layer with salt . Salt dissolves under the action of moisture and forms a dense crust. This eliminates the leakage in the sewer pipes.

Small holes can be sealed with baking soda and Moment glue or other polyurethane mixture. Soda is rubbed into a crack or hole, and then filled with superglue.


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Any stretch fabric and automotive sealant can be used. The fabric is impregnated with a waterproof liquid adhesive and applied to the area of ​​leakage in several layers. The mixture hardens from 6 to 24 hours, so this method cannot be called very fast.

Common repair methods

The repair method depends on the cause of the breakdown. If the siphon body or overflow pipe burst, the work comes down to replacing the device. In this case, you need to dismantle part of the system, install new parts and connect with existing ones, not forgetting the gaskets.

Siphon repair

Instructions for repairing an element are almost the same as cleaning it. The algorithm of actions is similar.

  1. Place a basin or other container under the siphon on the floor. Water from the water seal and debris accumulated in the tank will pour out here.
  2. Unscrew the lock nut and carefully remove the bottom cover. The connection is threaded, so you need to act carefully.
  3. Clean out the bend in the siphon using a screwdriver or a long wire. This removes not only clogging, if any, but also scale. If the layer of deposits inside the body is too large, it is better to completely dismantle the siphon and clean the base with chemicals.
  4. Inspect the O-rings. They must be intact, elastic and without pinches. If this is not the case, the gasket is replaced with a new one.
  5. Assemble the siphon in reverse order. The joint between the flask and the bottom cover is coated with sealant. If this does not help, the thread is wrapped with tow or FUM tape, then treated with paste, and only then the part is screwed on.

Sometimes a leak occurs at the junction of the drain and overflow pipes. Such a breakdown is eliminated with the help of cement mortar. The composition closes the joint around the entire circumference. After the cement ring has dried, the joint is treated with liquid glass or silicate glue.

Repair of metal siphon and pipes

In city apartments, the most common option is when a plastic siphon is placed on a cast-iron sewer pipe. Here, water can be released at the junction of pipes made of different materials. Usually this problem is solved by installing a seal on the coupling.

Metal siphon and cast iron pipes can still be found in old houses. Repair is carried out according to the same scheme, but includes additional work.

  1. Shut off the water, place an empty basin under the siphon.
  2. Unscrew the bottom cover. If the fasteners are “sticky”, use grease or machine lubricant to soften. In difficult cases, especially when the valve is to be replaced, the fasteners are cut off.
  3. If the thread also does not lend itself, and the cast-iron pipe will be used, the grinder cuts the adapter, and, if necessary, the siphon.
  4. Install the new element in the usual way. A new thread is cut on the old pipe to replace the removed one.
  5. Select a suitable piece of pipe and thread both ends. The segment is connected to the sewerage and the coupling-adapter on the siphon.

So that the threaded connection does not let water through, the joints are sealed with FUM tape or tow.

Why the siphon is leaking under the bathroom and how to avoid it

The siphon is leaking under the bathroom – a problem that can poison your life.

Reasons for leakage may be sufficient. We will consider the reasons why the siphon flows in the bathroom and how to eliminate them.


  • Why is the siphon leaking in the bathroom?
  • Siphon leaking under the bath – causes
  • The siphon is leaking in the bathroom: how to fix the leak

Why is the siphon leaking in the bathroom?

To begin with, let’s figure out what causes puddles to appear under the bath, in what situations they occur and how intensely this happens.

Tub siphon leaking

Tub siphon leaking – Causes

The most common ones are:

Tub drain clogged

  1. Rubber o-ring worn out, i.e. cracked, stretched, or moved out of place due to loose nut .
  2. The overflow pipe burst.
  3. The siphon was not closed tightly after cleaning.
  4. The bathtub siphon is dirty. You can read about the water seal device in the article on our website “Installing and replacing a bath siphon”.
  5. O-rings are deformed.
  6. The joint between the drain and overflow pipes is loose.
  7. Connections leaking due to stripped threads and damaged gaskets.

Bathtub siphon design

Siphon is leaking in the bathroom: how to fix the leak

1. If the ring is broken or stretched, also replace it with a new one.

2. If the overflow pipe is broken, replace it by installing a new one. To learn how to remove the siphon from the bath and change its parts to new ones, also read the article on our website “Installing and replacing a bath siphon”.

3. If the ring has moved, correct and tighten the nut well.

4. If the siphon is dirty, proceed as follows:

  1. To prevent dirt from getting on the floor, place a basin or some suitable container under the siphon to collect liquids.
  2. Unscrew the lock nut and carefully remove the siphon bowl (bottom cap) so as not to damage the integrity of the connection and the threads.
  3. Carefully clean the inside of the siphon using a long wire or screwdriver to remove any build up and any debris that has accumulated on the walls of the water trap.
  4. Screw the bottom cover back into place in reverse order. Important! Make sure the ring is in the same place.

5. If the O-rings have changed shape, this may be due to cleaning the siphon. And you will not be able to return the siphon to its place the way it was long before the current form. Therefore, it is better to change the siphon when you clean it.