Air lock in hot water system - help!

[joeblogger]

I had to drain the cold water tank to fit a new thermoelement in my Grohe shower.

When i refilled the cold tank i discovered I have an air block in the hot water system.

I think this is most likely because I ran the shower before the cold tank was full.

I have tried many methods to clear the air block. Hose between hot and cold taps, reverse hose washing machine method and holding palm of hand over shower room basin mixer tap to force cold water into the hot pipe.

I have a Stuart Turner 3 bar monsoon pump. After using the above methods I can get water to flow out from the hot taps briefly and the pump runs, then in slows to a trickle and stops. The pump stops.

I took off the hot in hose to the pump and cold water is gently pushing up on the hot side (as though it has crossed over in the pump).

The kitchen tap which is not pumped won't flow. The basement hot tap which is pumped will flow for a while, but only cold (even though the hot water storage tank is hot).

I'd really appreciate any advice - The hot storage tank is hot, but I can't get any flow from it. The pipe leaving the top of the tank has a valve, this is fully open, but no flow. I suspect there is air in the cylinder.

Thanks

Jerry

 

[kbdiy]

Pictures of the pipework around the cylinder and pump might help. Unlikely to be air in the cylinder as it should have an open vent pipe to the cold water tank. Did you drain the hot water cylinder too? If you didn't disturb the pump connections I can't see why that would be an issue now unless it needs priming again due to the drain down.

 

[longdogs]

Have you tried:

Running shower/taps with pump switched off?

Removing the hot in flexi and running water into a bucket

Looking for an obstruction at the tank connector

Checking to see if there any valves turned off

I am assuming that your pump is twin impeller so Hot & Cold should be separate and not able to mix unless connections are wrong.

Sorry if you have already tried the above - just thinking of the things I would check for.

 

[HERTS P&D]

Post a pic of the top of the cylinder.

Try holding palm of hand under kitchen mixer, forcing cold water up the hot side.

Andy

 

[ALCPlumbing]

Try taking the shower head off and running the shower. The head restricts the flow quite a lot and without it the pump maybe able to draw the air out.

 

[joeblogger]

Thanks for the thoughts.

Had to call in the professionals (my friendly local plumber Dave Halpin from Gasworks London) in the end when i realised I definitely had air in the hot water cylinder (caused by running the shower when the cold water header tank was empty, thus pulling air into the hot cylinder to replace the hot water pumped out of the cylinder).

From this article:http://www.diyfixit.co.uk/central-heating/hot-water-air-lock-vented-system.html


So I knew the solution by this point, but wasn't sufficiently confident to try it - feed mains pressure cold water back down the hot water cylinder vent pipe (the one which feeds back into the cold water storage tank) which forces the air out of the cylinder into the cold header tank. In other words reverse the normal flow of things by feeding water into the top of the cylinder rather than the bottom.

A huge amount of air bubbled back into the header tank, and all hot water was restored.

So lesson learned - don't run the hot water when the cold header tank is empty!

Thanks for the help.

Jerry

 

[longdogs]

Or use rubber bungs when changing s valve

 

[joeblogger]

Yes, you are right - don't waste time (and water) draining the cold header tank when you could use bungs to block the flow. That is the other thing I learned. My friendly local plumber was nice about that too.

Jerry