How to Fix a Leaking Overflow Pipe – A Practical Guide 

Let’s be honest: no one is thinking about the state of their overflow pipes. However, you’ll want to start fixing the plumbing issue as soon as the overflow pipe starts leaking.

Neglecting a leak for extended periods will damage your home or property, and water leaks can cause damp damage, resulting in costly and complex repairs.

According to Checkatrade, damp proofing costs per metre range between £50 and £75, and a damp survey costs between £100 and £600.

Fixing the cause of a leaking overflow pipe is a far easier job to accomplish.

Now that we’ve given you a sneak peek, what is an overflow pipe?

What Is An Overflow Pipe?

Before we get into the nitty-gritty or repair guide of fixing a leaking overflow pipe, let’s understand what it is. An overflow pipe, often hidden but common in UK homes, is attached to appliances, water tanks, toilets, baths, and sinks.

Its primary function is to prevent excess water from spilling, creating a mess, or causing dampness. Usually, the overflow pipes drain out of the home into the stormwater system outside.

An overflow pipe is also installed in the home to ensure the water can drain outside if a tap runs into a blocked sink. Most overflow pipes are made from 9mm PVC and are fitted at a gradual slope to ensure water flow goes outside.

Overflow pipes are integral to your home’s plumbing system, but they can’t stop some minor issues from developing into more complex problems. Thus, the alarm bells should go off when overflow pipes leak.

Technically, the overflow pipes we’re talking about are just working to indicate there’s a problem, not to solve it.

Now that we understand what an overflow pipe is, why is it leaking?

Why Is The Overflow Pipe Leaking?

Overflow pipes are often used as a collective noun for multiple items, so the reason why one may be leaking can vary widely. As mentioned, leaving an overflow leak of any size for a prolonged time can damage your property.

Most issues associated with a leaking overflow pipe are not dangerous. However, be aware of where in the home the overflow pipe leaks, as it can cause significant damage or become a hazard.

For instance, a leak from a boiler’s overflow pipe can be extremely dangerous, so you’ll need to contact a Gas Safe registered boiler engineer to do the repairs.

So, where does a homeowner start to look for the source of their leaking overflow pipe?

Diagnose Where It Could Be

As we mentioned, your home has many appliances and fixtures that use an overflow pipe. These overflows are usually in similar positions due to their corresponding appliances and fixture functions.

If you’ve noticed an overflow pipe dripping at the ground level of your home, it is usually associated with cold water fixtures, like a toilet.

Appliances and boilers have an overflow pipe on the roof, dripping into your gutters and the stormwater system. Knowing this will help you narrow down your search.

If the water you discover is warm, this is a serious problem. Appliances that heat shouldn’t divert warm water via the overflow pipes, as they need to retain it to ensure it doesn’t damage itself. The overflow water should only be cold.

Sometimes, locating the leak is simple enough, such as discovering pools of water at the base of the fixture or appliance. These puddles of evidence will be more visible first thing in the morning as the water pressure pushes out the liquid overnight.

Before starting to work on any leak, make sure you know where the switch-off valves to the appliance, and/or the mains are located and how they work. There’s nothing worse than discovering you should have turned off the water supply.

If you still haven’t found the source, you will want to check the entire system’s water pressure.

Check The Water Pressure

Increased water pressure is a prevalent issue that can cause leaking overflow pipes. As you can imagine, high pressure can strain the system’s pipelines, causing leaks over time.

Some homes’ overflow pipes have pressure valves to indicate the flow rate. Your system’s pressure can increase over time if the valve starts to loosen or the washers spring a leak due to wear and tear.

The more the system leaks, the more pressure is required to maintain the optimal flow rate, which in turn will damage the overall system.

The cause will be easier to confirm with the help of a plumber who can use moisture sensors to locate the issue. Also, if the pipe is in the wall, you’ll need the professional help because they will have to chisel into the wall to work on it.

But what jobs can you do yourself to fix a leaking overflow pipe?

Overflow Flow Repair Guide

Most homeowners can conduct their own repairs but we always recommend that you know when to ask for help.

The first repair is a common issue.

The Float Valve

Here’s an assumption: most homeowners will know how problematic a float valve can be.

It is one of the most common issues that could lead to an overflow pipe leak and flooding from a cistern or water tank.

Float valves control the water level and usually comprise a plastic ball (that floats) attached to a metal arm. Most people will have encountered a float valve in their toilet cisterns (orange floating ball).

However, this valve is also used in cold water tanks or as part of a central heating feed and expansion tank.

The float valve works by floating with the water level, and moving as the levels go up and down. It turns off an external water source when the arm reaches a certain level. If the valve doesn’t work, the water will continue flowing in and flood the system.

If the water level gets too high, the overflow pipe will not work correctly, also flooding the surrounding area.

Before starting any repairs, switch off the water supply. Typically, your toilet’s supply tap is next to the supply pipe that comes out of the wall behind or under the cistern of your loo.

You should also remember to flush the toilet to empty the cistern.

Here’s a brief checklist to ensure your float valve works and how to fix it.

• Check whether your float valve is moving freely. If it gets wrapped up in a loose chain or wire, untangling it could be an easy fix.
• You might need to regulate the float valve, which is simply controlling the extent that the float valve moves by bending the arm (usually made of a bendable wire) or just making some adjustments to the screws holding it in place.
• If the float valve is not shutting off the water flow properly, it might be time to switch out the washers. Washers are usually round and made from rubber, ensuring that taps and pipes retain water under pressure.

But if this isn’t the issue, here’s another reason your overflow pipes might be leaking.

Expansion Tank and Cold Water Feed

If your home has an expansion tank, it will be fed by an external coldwater outlet via a cistern. This cistern monitors the water flow into the expansion tank to ensure that the pressure in the system doesn’t build up.

Expansion tanks are usually needed for a closed-loop heating system, with the coldwater feed ensuring that pressure remains constant.

But what’s causing the overflow pipe to start leaking? There are two possible common causes:

• The water feed into the tank is not turning off
• The water in the tank is being pushed back up the outlet pipes

You can peek inside the tank to confirm that the water inlet feed into your tank is not turning off. If there is a constant drip from the water feed, you must try adjusting the float valve, replacing it, or changing the washer.

As discussed, if the problem is the toilet’s float valve, this task is simple. But if you’re not confident in your abilities, call in a professional to help.

In the second scenario, the water is being pressured back into the outlet pipe. These pipes feed water to your taps and water cylinder.

This pressure buildup will eventually result in a leak when you use a specific mixer faucet in a shower or other plumbed-in fixture around the home. When the problematic tap is used, you can confirm this is the issue; the overflow will start leaking again.

This job is best left to the professionals, as it can become incredibly complicated.

Let’s focus on the next culprit for a leaking overflow pipe!

Central Heating

If the overflow pipe extending from your home’s roof is leaking into the gutter, you should check the central heating. Most central heating systems are located in the loft or attic of your home, but even if this isn’t the case, just know its overflow pipe will still be situated on the roof.

There are two potential issues that can cause an overflow pipe from the central heating to start leaking. One of which is a common element: the water feed is not stopping.

Your central heating system needs to maintain a constant heat level. This heat level is lowered if the float valve works correctly and the washer has not deteriorated.

If you can see or hear a constant flow of water, even drips, you will want to ensure that the float valve works.

The next culprit is a problem with the hot water cylinder. We’d recommend calling a professional if the water cylinder is acting up.

A hot water cylinder is usually well-insulated, and with a large heating element inside, it can be fairly dangerous to work on if you are not well acquainted with how it works.

The Boiler (sort of)

While boilers don’t have an actual overflow pipe, they do have a pressure relief valve. It’s important this valve works. If a boiler is under too much pressure and can’t release the pressure, there will be a major problem.

The relief valve is also placed outside the home. This pressure relief pipe usually releases liquid onto the roof, which flows into the gutters and away from your home via the stormwater system.

If you see what you think is a leaking boiler, call a professional as soon as possible. This “leak” indicates excessive pressure in the system due to a valve issue.

For those who keep their boilers serviced, this shouldn’t be an issue.

Also, make sure it’s not the condensation pipe. The condensation pipe only works when the central heating system is turned on, and hot water flows through it.

Our next overflow is pretty easy to spot.

The Sink

Most sinks have a hole near their rim. This hole is the overflow inlet for your sink. Overflow inlets are also found in baths, basins (kitchen and bathroom), and more.

These overflows ensure your home doesn’t flood if you forget to turn off the tap. You will not see this overflow pipe outside the house because it is plumbed straight into the drainage pipe.

This overflow could be caused by a drain blockage, but if this isn’t the case, you will most likely just want to remove the plug.

When in Doubt About Your Overflow Pipe…

Call a professional to help. Don’t mess about if you’re unsure what is causing one of your overflow pipes to leak.

As the old proverb says, “A stitch in time saves nine.”

So, rather than requiring a major renovation of your property due to damp, make sure to fix that leaking overflow pipe as soon as you can.

And you can chat with one of our eager consultants in the chat window located on the bottom right of your screen.