Overflowing Expansion Tank = Wet Floor and Worrisome Wife.

[TonyW2]

Quite!
And if the coil is burst, the ch expansion tank would be continually filling.

However, as the OP says that there is now no overflow or f/e tank water level increase , I guess we may never know.

The dhw vent pipe does need adjusting so the discharge is above the storage water level, to prevent syphoning, but I guess this is a seperate matter to the overflow troubles.

 

[tryitandsee]

Just thinking out loud.

Does the op have a side connection to the hot water cylinder for his hot supply to the power shower or a top one. I still think for some reason the power shower is pulling water down the vent pipe that is submerged in the cws tank and causing the expansion tank to fill. Can this happen? I thought the vent normally discharged into the f&E tank. Is this vent pipe a joint fill and vent?

 

[yeahdisk]

Thanks for all the replies.

I've re-done the overflow so it won't get an airlock again. I'll shorten the HWC vent tomorrow morning. Do you really think it is possible that water could be siphoning out of the cold storage and finding its way into the expansion?

I really appreciate all the help - I'll post back ASAP if something happens again.

(For what its worth, I've just checked the expansion tank again and it hasn't raised at all.)

*Edit: In answer to the last post, Hot Water to power shower is taken from the side of the HWC (essex flange)

 

[seco services]

I still think for some reason the power shower is pulling water down the vent pipe that is submerged in the cws tank and causing the expansion tank to fill. Can this happen? I thought the vent normally discharged into the f&E tank. Is this vent pipe a joint fill and vent?

the cylinder vent should be in the cws
the only vent in the f/e should be the vent from the heating side.

the only way your hot water can pass to the heating primaries is through a failed coil.

i would say you had a restriction in the primaries causing the water to go up the vent/cold feed.

 

[yeahdisk]

Thanks again for the response...

So, just to confirm, the only way I could get additional water into my expansion tank (discounting a faulty ballcock valve) is water transferring from the HWC, through a broken coil, into the heating side and out of the vent?

Hence a new HWC is required?

Is there a way that test this hypothesis (because it certainly isn't happening now).

 

[seco services]

as said before if the coil had failed the f/e would keep filling and the cws would be filling aswell but from the ball valve.

i think you either had a partical block in the heating primaries one off.
just keep eye on it.

 

[TonyW2]

Yes that is the situation, but if the coil was split, and as the c/h f/e tank is lower than the big cws tank water, it would happen all the time.
Therefore as it is not happenning, don't rush to buy a new hw cylinder!

IMO the submerged vent intothe cws tank is a red herring and all that has happenned is that the blocked f/e central heating tank overflow coincided with a weeping f/e tank ball cock valve.---all of which you have fixed.
Keep an eye on things.

 

[tryitandsee]

Serco is probably right.
Have you watched the tanks whilst someone else is having a power shower. It may show up some anomalies.