Drainage Problems? It Might Be Air Pressure

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Drainage Problems? It Might Be Air Pressure

March 10, 2025

Do you have strange gurgling noises coming from drains?

A manhole cover with water coming out of it and a house in the background.

As drainage engineers, one of the most common calls we get is about strange gurgling noises coming from drains.

Most homeowners are surprised when we tell them the culprit is often something they can't see - air pressure in their pipes.

Let’s share a recent example. We visited a property in Basildon where the owner was bothered by bad smells and slow-draining sinks.

The cause? Poor air circulation in their drainage system. It's a problem we see time and time again, but thankfully, it's one we can fix.

What's Actually Happening in Your Pipes?

Think about what happens when you flush your loo or empty your sink.

That rush of water needs to go somewhere, right? As it flows down, it pushes air through the pipes too.

Without proper ventilation, this creates a vacuum effect - much like what happens when you drink through a straw.

This vacuum can cause all sorts of hassle:

Your sink might drain slower than a snail
Weird gurgling noises that sound like a swamp monster
Nasty smells wafting up from the plughole
In the worst cases, dirty water backing up where you definitely don't want it

A faucet is pouring water into a stainless steel sink.

The Fix: Two Ways to Solve It

In our regular callouts across Essex, Kent and London, we typically use one of two solutions:

1. The Traditional Vent Pipe

Picture a pipe that runs up through your roof. Simple but effective, it lets fresh air into your drainage system. It's like opening a window in a stuffy room - it just works

2. The Clever Little AAV (air admittance valve)

Sometimes called a Durgo valve, this smart bit of kit is our go-to solution when a vent pipe isn't practical. Think of it as a one-way air valve - lets air in when needed but keeps the smells locked away.

Which One's Right for Your Home?

From our experience working in hundreds of properties around Essex:

Got a standard two-storey house? A vent pipe usually does the trick
Living in a taller building? An AAV might be your best bet
Converting your loft? Definitely consider an AAV
Got neighbours with windows overlooking your roof? AAV all the way

Fitting an AAV: The Nuts and Bolts

If you're thinking about installing an AAV, here's what we've learned from years on the job:

Keep it somewhere with good airflow - loft spaces work well
Make sure it's at least 200mm above where water normally sits in the pipe
You can choose push-fit (quick and easy) or solvent-weld (more permanent)
Some can go outside, but check they're proper outdoor ones (look for the kitemark)

When Things Go Wrong

A close up of a hole in a pipe with a light coming out of it.

Even the best solutions can play up sometimes. If you notice problems:

Check nothing's blocking the valve
Make sure it's fitted high enough
Look for any obvious damage
If in doubt, get a professional to take a look

A Word of Warning

While DIY can be tempting, drainage systems can be trickier than they look. We've lost count of the times we've been called out to fix DIY jobs gone wrong. If you're not confident, it's worth getting a professional in - it often saves money in the long run.

Need a Hand?

Having drainage troubles in Essex, Kent or London? Our team's available and we never charge for callouts. Whether it's a simple AAV installation or a more complex drainage issue, we're here to help.

Got any questions about your drains? Drop us a line - we love talking about this stuff (even if most people think we're a bit odd for it!).

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