Air Locked Domestic Hot Water

air

Hi,
The mains water was off in my house a few weeks ago and the hot water system got air locked and now I dont have more than a short trickle of water from the hot taps upstairs or downstairs.
I tried using the mains pressure to push the air lock up (using mixer taps downstairs) but this didnt do the trick even when I left one over night.
Its a standard semi detached house, gas fired central heating.
Any possible solution suggestions would be appreciated.

Corkey123

Air

Was the storage tank emptied? If so it is likely that the air is at the highest point above the Hot water tank. Have a look as there as some of the older systems can have a valve there for bleeding air from the system.

JamesM

If the tank in the attic is full to the top, or its usual level, there should be good pressure at the taps. If you have tried to clear the airlock, then mabe some dirt was stirred up in the tank and is blocking the outlet, or the pipe from the tank.
When you connect the mixer in the kitchen (block off ?) and turn on the hot and cold, does water push up into the tank in the attic ? Also try opening the other hot taps in the house and see what the flow is like. It will give you an idea if pipes are blocked.
Jim.

air

If I open all the hot taps they eventually all stop and nothing comes out.
When I backflowed the cold up through the hot using the mixer for a day, I got a good flow out the bottom all right but it stopped again eventually.
I'll check out the tank tonight, I think there's just one up there, I assume this keeps the hot water cylinder topped up and then the hot water is fed from there to the taps?
I know bugger all about plumbing.

JamesM

air wrote:

If I open all the hot taps they eventually all stop and nothing comes out.
When I backflowed the cold up through the hot using the mixer for a day, I got a good flow out the bottom all right but it stopped again eventually.
I'll check out the tank tonight, I think there's just one up there, I assume this keeps the hot water cylinder topped up and then the hot water is fed from there to the taps?
I know bugger all about plumbing.

It sounds like the tank might not be full, or filling properly - is the water close to the top ?
Although, if there is good pressure in the upstairs cold taps, there is probably enough water in the tank.
The tank supplies all the hot water and probably the upstairs cold water and the toilets.
Jim.

air

Hi all, thanks for the replies.
Jim, yes, I've just checked the tank and its full to the top all right and there's nothing blocking the outlets to the hot or cold supplies.
I've attached two images of the tank and hot press set up in the hope that they might help.
This first one is the arrangment in the hot press.



And this is how the tanks is plumbed

reg_anam

I know its sounds a bit obvious but are you absolutely sure the stopcock/s are/is open in the hot water system ?

air

Yeah I checked them
The system was working fine before the water went off & I didnt change anything.
Besides a small amount of water makes it to the hot taps, its just that the flow reduces and then stops if a tap is left open.

JamesM

I'm no expert, and none of the plumbers have chimed in yet
It seems to me that the 2 blue pipes to the left of the cylinder are the cold feeds to the cold taps and the cylinder. They are red in the 2nd drawing. The red to the left of the cylinder is the hot flow to the taps. and it becomes the yellow one in the other drawing overflowing into the attic tank. The blue to the right of the cylinder is from the gas boiler feeding the coil in the cylinder.
My only guess would be that the valve on the blue going into the bottom of the cylinder is half blocked (maybe dirt stirred up in the tank when the water started flowing again) or faulty and only letting a certain amount of water through. Maybe try turning this valve on and off a few times and see if it clears.
Jim.

air

JamesM wrote:

I'm no expert, and none of the plumbers have chimed in yet
It seems to me that the 2 blue pipes to the left of the cylinder are the cold feeds to the cold taps and the cylinder. They are red in the 2nd drawing. The red to the left of the cylinder is the hot flow to the taps. and it becomes the yellow one in the other drawing overflowing into the attic tank. The blue to the right of the cylinder is from the gas boiler feeding the coil in the cylinder.

Yes that was my guess as to how it was working.

JamesM wrote:

My only guess would be that the valve on the blue going into the bottom of the cylinder is half blocked (maybe dirt stirred up in the tank when the water started flowing again) or faulty and only letting a certain amount of water through. Maybe try turning this valve on and off a few times and see if it clears.
Jim.

I fully closed and opened it just to make sure that it wasnt half open & it didnt make any difference.

On a separate point, to get maximum value from the central heating loop, am I right in thinking that the lower ball valve on the right hand side of the tank should be left fully open?
Thanks again.

air

Just a bump to keep this on the front page

JamesM

air wrote:

On a separate point, to get maximum value from the central heating loop, am I right in thinking that the lower ball valve on the right hand side of the tank should be left fully open?
Thanks again.

Yes, normally it should be fully open to get a good circulation through the coil.
Jim.

JamesM

air wrote:

On a separate point, to get maximum value from the central heating loop, am I right in thinking that the lower ball valve on the right hand side of the tank should be left fully open?
Thanks again.

Yes, normally it should be fully open to get a good circulation through the coil.
Jim.

Avns1s

Two options:

1. are there any compression joints you could open to let out any air? Obvoiusly not an option if the joints are the soldered type.

2. You could try sucking water/ air through the tap. Great exercise for the lungs and cheeks.

Sometimes a little air at a wrong spot, can cause a lot of trouble and it can sometimes take very little to release it.

You could also try backfeeding from the mains THOUGH IF YOU HAVE GOOD WATERPRESSURE THEN YOU RISK EXPLODING YOUR COPPER CYLINDER.

air

Hi Avns1s, I've already tried backfeeding through the mains, didnt even manage to get an explosion

I had another look today and there is a drain valve at the elbow on the pipe entering the bottom of the cylinder. (The blue line entering the cylinder at the bottom left hand side in the first sketch).
I opened this and drained several litres of water from it and there was full flow for the size of the opening which leads me to believe that there is no problem between the tank and the cylinder on the supply side.
I also tried closing the valve in the line but of course water kept coming (presumably the contents of the cylinder coming out).
I'm pretty puzzled now, it seems a pretty simple system.
Also there was no sign of any dirt or anything in the tank in the attic, it is well covered over.

Avns1s

Ok Air,

Did you try the "sucking"? Did anything come out?

(Don't anyone let their minds run away with the questions!!!);)

air

LOL, I wont be back in the house untill next week, I might give it a go then.

rogue-entity

You tried backflushing from the cold mains through the affected hot taps, and in each case, water came back out, but stopped. When this happened to us, it was because our storage tank had run dry because of a broken ballcock in a toilet fed from the rising main. You said your storage tank was full, and that with the cold feed closed to the cylinder, and the drain cock open, water was coming from the cylinder, so their is no problem between the cold feed and the cylinder.

This suggests to me that the air is trapped between the head of the cylinder, and the point where the pipe at the top splits, with feeding the hot taps, and the other running to the storage tank (the yellow pipe in your drawing).

You could try the following: Backfeed one of the taps, and check to see if the water is venting from the expansion pipe in your attic, if this is happening it means that their is a clear path between your hot taps and where the feed for the taps connects to the pipe leaving the cylinder, and the air is below that connection. If that is the case, Run the hot tap until the water stops again, close the cold feed to the cylinder, and loosen the connection on the top of the cylinder, if water escapes, wait until it stops, which it should. Then open the cold feed until water starts to escape again, just to make sure no air is trapped in the top of the cylinder. Tighten the connection, and loosen the one right below the T junction (where the feed splits to supply the hot taps), and see if any air their escapes. Their should be some air trapped.

I am not a plumber, but I am handy with the DIY, and I have bled air from our own system on two occasions because of problems with the pressure in the rising mains (it splits and feeds some of the upstairs cold taps, and toilets for some reason).

311

Hello ,sometimes when valves are closed and opened again they get stuck.
They only open slightly ,which sounds like what has happened here maybe?

Turn the valve feeding the cylinder off ,Break/open the nut on the bottom of the valve feeding the cylinder.Turn it back on and check to see if it is letting out water (Only do this if the valve is higher than the cylinder!!)

Other than that ,get a loan of a wet hoover and try and suck the air from the pipe ,if it's airlocked.

Give me a shout if your stuck with a PM ,I've not much time at the moment to check posts.

Happy Days!

air

Hi all, just to wrap this up and say thanks for all your help.
The problem turned out to be insufficient incline on the pipe that runs from the top of the hot tank to the tank (the expansion pipe).
I increased the level of slope between the point where it enters the attic and where it enters the tank and it solved the problem. The shallow angle was allowing air to be sucked in I guess.

Thanks again for everyone's help.