Sink Drain with Plunger

Is the water in your sink not draining away properly? or even not at all? Sounds like there is a blockage somewhere in the system. You may think this is an expensive job to get someone out, but this problem can usually be solved without the help of a plumber, and it will take you no more than 30 minutes.

Mostly, slow drainage in your sink would indicate a blockage somewhere; a build-up of dirt and debris that has accumulated over time but another reason for this could be an airlock in the system, so we are going to have a look at how to fix it.

What is an Airlock in a Drainage System?

Airlocks, (also called vapour locks) are common in pipe systems that have been installed without proper ventilation.

An airlock is a pocket of air that has no way of escaping therefore creating pressure that prevents the natural flow of liquid through the system.

An airlock or other blockage may manifest itself as the sink draining particularly slowly or the drain making gurgling noises as the water drains away.

How To Fix an Airlock in a Sink Drain

To fix an airlock, you will need to treat it the same as any other blockage and be prepared. So firstly, we recommend getting a few things together so you can sort this problem out quickly and efficiently with no mess.

What You Need

  • Gloves
  • Plunger
  • Towel
  • Bucket
  • Drain Unblocker
  • Drain Rods
  • Old Brush
  • New AAV (Possibly)

1. Check for a Local Blockage

First of all, we need to investigate whether it is actually an airlock in the system or if there is a build-up of dirt and debris clogged up somewhere.

There are a few things you can do to check if there is a local blockage:

  • Run boiling water down the sink
  • Use sink/ drain unblocker
  • Use a plunger
  • Remove and clean the trap (There are different types, but this is the fitting we mostly call the U-bend)
  • Use drain rods
  • Lift manhole to ensure blockage is not at your main drain

Once you have potentially ruled out a local blockage by doing the things mentioned above, you can move on to step 2.

2. Locate Your AAV

Once you have ruled out a blockage, you will now want to locate your AAV. An AAV (air admittance valve) is used to allow air back into a system to keep it balanced and the water flowing correctly.

Note: In the UK AAV’s are usually found in the loft although some individual fixtures may have their own; particularly if the fixture was added after the house was built and is not directly plumbed into the original pipework.

3. Inspect the AAV

Once you have located your AAV, inspect the valve. If your AAV is seized, remove it and clean out any debris that may block it.

If unsure, please see the below video on how to maintain your AAV.

4. Test

Once you have inspected and cleaned your AAV (or replaced it if required), you can now test that your drain is working properly.

What to Do if this Doesn’t Work?

If cleaning the AAV has not had the desired effect, this means that there IS a blockage elsewhere that you have not yet located.

If this is the case and you want to try and fix the problem yourself, you can try and flush the stack by using a hosepipe and jetting the water down it from the top or using drain rods down the manhole outside.

Alternately, call a plumber out to assist you.

Conclusion

If you’re experiencing a slow sink drain, there’s a good chance that there’s an airlock obstructing the water flow.

This guide provides easy instructions on how to locate and remove the blockage using basic tools and supplies that most people have at home. If these methods don’t work, it may be necessary to call in a professional plumber to diagnose and solve the problem.

Plumbing Wizard Tips

“If unsure, call out a plumber to take a look for you!”

“Before checking the AAV, exhaust the possible local blockage options in the drainage system!”

“Make sure that you check for an AAV around the sink that is causing the issue as it may have its own!”

“Make sure that you wear gloves, you may also want a respirator too as you may end up encountering sewer gasses when you remove the AAV!”

Frequently Asked Questions

What is a Durgo valve?

A durgo valve is another name for an AAV (air admittance valve). An air admittance valve is a one-way valve that allows air to enter the drainage system when the water leaves it. This prevents negative pressure from building up in the drainage system, which can cause water backups – they are also designed to prevent noxious sewer gasses from entering the home.

When should you use an air admittance valve?

Air admittance valves should be used in plumbing systems whenever there is a need to vent appliances such as dishwashers, washing machines, or toilets while preventing the backflow of sewer gases into the building. They are also useful for venting traps on sink and lavatory lines where a continuous vent cannot be maintained.

Where should I place my air admittance valve?

The air admittance valve should be placed at the highest point in the drainage system. This will ensure that the valve is open when water accumulates in the drainage system and will allow air to enter, which will help to prevent a build-up of pressure and eventual overflowing of the drainage system.

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