Periodic Airlock

[Onoff]

I've a cold water storage tank one end of the house that feeds a downstairs bathroom bath cold and upstairs ensuite basin cold.

It runs across the dormer in 22mm from the cws tank then drops in 15mm to a tee. It runs in 15mm to the basin cold via a ball valve, it runs in 15mm to the bath via a gate valve.

Periodically the upstairs basin cold slows to a trickle then stops altogether.

To get the basin cold going I have to run the bath cold, then the basin, then close the bath feed off after the tee and it clears the air to the basin tap.

Sometimes it's ok for months. I got it going the other night and it stopped again with 24 hours.

There's a stop end mark X just floating in mid air in the loft. If I put an air release valve like this there, would that alleviate the problem?

 

[Agroshield]

What you have drawn horizontal with stop end on it, is that significantly higher than the basin outlet?

Maybe consider a non-return valve near the tee at the other end of that run. It could be that the bath is trying to pull a vacuum on the basin feed.

If you could angle the stop end run, so the proposed air-release is leg is higher than the other leg of the tee (or the non-air release leg dives down after the tee), it will encourage any air to go towards the release valve. Best would be a tee with two vertical legs and the air valve in the top one. With two horizontal legs, you might only catch 50% of the air at the release valve.

 

[gaz1]

its more like the bath has run out of water from the tank and starts to draw air in

try first with stopping the water before you need wait 1 minute for the tank to catch up a bit then finish off filling

alternative is to fit a bigger tank up there

 

[Bladevane]

Could it be that the CWS tank does not have enough head to feed the upstairs basin? We had a similar situation in our converted bungalow with the hot water. Previous owners had fitted a MIRA booster pump with float valve but even this wasn't the answer. As an attempt to resolve the problem I installed an automatic vent valve to the hot line with the vent connected to the basin drain. Still wasn't the answer though. As part of a major upgrade we went fully pressurised on all hot and cold and the difference was amazing. I would caution against using automatic vents which can have the vent left open as they often leak, and then you're into a whole world of pain.

 

[Agroshield]

I would caution against using automatic vents which can have the vent left open as they often leak...

In this case, a possible option to cancel the effects of this would be to extend the stop end leg with plastic pipe and put the vent above the top water level in the feed tank.

It it worth checking out the suggestion above that the tank might be emptying faster than it can fill - put the bath on full and see if the inflow to the header tank keeps up.

Another diagnostic would be to connect some clear hose to the basin tap, fill the sink and leave the end of the hose in the water. Open the bath tap and leave running then open the basin tap - if water is drawn up the hose, the bath is tryinh to suck from the basin leg.

 

[Slowcoach]

I’m certainly no plumber but () would putting a tee at the top where marked help, and then an air admittance valve, although if it used to be ok maybe something else is amiss.
How long is the pipe with the stop end on, aren’t they supposed to be as short as possible?

 

[Nomad]

Hi. I've had houses where bleeding the pipes was difficult but they only had problems after I'd done work on the system and got air into the pipes. How is air getting into your (closed) system? As suggested above, run a bath and check the header tank in the loft can supply the demand - if the header runs dry that is your air entry. Then run a bath and sink tap at the same time - is demand draining the tank? Is the bath creating negative pressure at the sink and pulling air in?
A mate started to get air locks when he fitted a power shower, fixed by putting another header tank next to the original to double the available supply.

The place I'm at now often gets air in the system, I find it clears best by filling the bath (22mm feed pipes) until the there are no more air bubbles. If I try to clear it using the sink (15mm pipes) I never get a good result.

 

[Smallfry]

IMO the run with the stop end runs slightly uphill, and gradually collects air. Although I have to say is a bit odd, because once the system is purged, I wouldnt have though you would get air in ??? Who knows, water systems are strange things.

I do not like those auto air valves, I have had them leak in the past.

Best solution I can see, if at all accessible, is to do away with the tee, the one before the stop end, and replace with an elbow to the basin, and try to get that run level if you can. Would most likely have to use a compression elbow, as once the system has had water in it, the are sometimes a bar steward to solder.

 

[Nomad]

In this case, a possible option to cancel the effects of this would be to extend the stop end leg with plastic pipe and put the vent above the top water level in the feed tank.

A good suggestion, it won't stop air getting into the system but at least any air will clear without you having to do anything.
It would still be best if you can find how / where / why you are getting air in the first place..

 

[dave h 2]

In some areas the water is so hard the ball valve seizes up with deposits which is when you find slow filling tanks.
A visit to the CW tank when the bath is running would confirm the question
Giving a closed water system more than one route to find air can mean your extra vent empties first and not the tank.

 

[Onoff]

Found some old pics from when I took down the downstairs bathroom ceiling inc the joists and replaced everything. This was the view of the dormer wall, as viewed from the hip end.

I remember now, that (grey lagged) stop end pipe used to feed the upstairs ensuite WC. (WC now on mains). Ensuite basin still on CWS tank.

 

[Onoff]

All these mention of air valves is totally unnecessary if a riser pipe is fitted at the air-lock point. The breather pipe simply needs to terminate well above the level of the loft supply tank (and preferably above that tank).

The other simple alternative is to feed the basin cold with a mains pressure supply. OK with separate basin taps, but maybe not so with a single mixer basin supply valve (the kitchen sink mixer works perfectly OK with the cold fed from the mains and the hot from the roof tank)?

Kitchen mixer tap is mains cold, cylinder hot.
Main bathroom the same. They work fine.

Ensuite is cold water storage tank cold and cylinder hot. I was at one time going to put the cold on mains but there's a long 15mm pipe under the floor of the upstairs ensuite and I'm not sure what the joints/fittings are like, how well supported etc.

Cloak basin, (separate taps), I can't even get to it! SWMBO is as bad as me for hoarding Think I disconnected the hot and it just has cold water storage tank cold.

 

[Onoff]

I put a check valve where the red dot is and it appears to have cured the issue.

 

[MetalMonkey]

I'm sure you are already aware, but dead legs are verboten. Even if it isn't your issue, getting shot of it isn't a bad idea anyway.

 

[dave h 2]

A dead leg at work gave us legionnaires in the shower when it was tested luckily no one caught it and we all had a day off.