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Would love some help with this. We're experiencing an air lock preventing cold water running in the upstairs bathroom/toilet.
We've a cold water tank in the loft. Every 3 months upstairs cold water stops. We've a bath, electric shower, toilet and basin. I then run a hose from our outside tap (mains I assume), jam it up the bath tap, turn bath cold tap on, turn outside tap on and after 1-2 mins hear a big gurgle from the loft. Cold water then resumes upstairs.
It's happening regularly, every 3 months or so. Why? What causes it? And how to prevent it?
Many thanks
Add a automatic air admittence valve vent. Follow the pipework. The blockage is probably ina bit of pipe where there is a loop up then down. I.e. an "n" or "^" shape or similar. Place aav at top of this loop.
Don't add an AAV, they are well known for eventually letting water out after a period of time.
Better to find the section of pipe that is falling the wrong way and alter that. It is most likely to be a high level section in the loft, especially if there is a long horizontal run. If it affects the whole of upstairs it implies that it is common to all the outlets that are suffering.
Bear, you're right, there's a long section from the tank along the loft and then a 90 degree bend to enter the bathroom. The long section is close go horizontal...is this the culprit? Do I need to make it less horizontal?
Yes I would start with that section. How long is it and what diameter is it?
Surely you will only get air locks in a tank fed cold feed by pulling air in from the tank? So presumably the mains supply can’t keep up with the demand. Can you up-rate the supply pipe or run a second storage tank in parallel with the existing.
As for aav’s, never had a problem with them and must have fitted hundreds.
Cheers, Paul.
Has the ball valve furred up with corrosion?
I'd say it's about 10' long, not sure of diameter. It enters the water tank halfway down. Ball valve is quite furry.
If the cold supply out is halfway down the tank then that is probably the problem, should be a couple of inches up from the base.
Does it supply a hot water cylinder as well?
If so, open the hot and cold bath taps and see if the water level in the tank drops enough to pull air in.
Intermittent flow could cause an air lock. Usually caused by long horizontal sections of pipework at high level, with a big drop at the end of it. The vertical leg of pipework empties faster than the horizontal section can fill it thus causing air locks. Water contains air too and it will separate out in high spots etc.
As others have said pipe should be lower than halfway down, and it should be lower than the cold feed that supplies the cylinder to prevent the chance of someone being scalded.
Check the rate the ball valve fills too, if it is a part 2 ball valve the washers get ‘lazy’ and don’t fully open.
I’ve fitted loads of AAV too mainly because they are being replaced as the previous one was leaking. Usually on heating systems. An AAV should be a last resort for this sort of problem, it shouldn’t happen on a properly designed system.
Great, v helpful and think I get the gist of it. Will investigate! Thanks
I assume you've checked the cold water tank to ensure there's nothing in there that could block the outlet? Thinking dead animal, wood or polystyrene floating in there.
Jeffl, no obvious sign of blockage...figure it'll be worth replacing the ball valve as a first sensible step