cabby

Central heating expansion tank

14 posts in this topic

Our thermostatic shower has been playing up - water only coming out when on a hot setting.  I suspected an airlock but couldn't clear it from the shower so checked up in the loft.  I found the expansion tank was empty and the feed valve turned off.  Not something I have done so assume when we have had work done at some point it was isolated then (cannot for the life of me think who and when! might have done this as would call them). 

 

Anyways, I turned the valve to the expansion tank on, it filled, some air bubbles appeared from one of the outlets and now the shower works :).

 

Should I leave this turned on + what are the consequences of not doing so?  My dilemma is that we are about to go away for a week and wondering if this was isolated due to a problem that we weren't told about i.e. a bodged fix.  Don't really want to come back to a flooded house.

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Most traditional indirect systems have a central heating header tank which via a ball valve is kept topped up and is used to keep the rads full of water.

There is a second, larger tank which provides the water for the boiler to heat and is then stored in the HW cylinder, this tank also tends ( to feed (but not always) wc's and occasionally bathroom CW feeds.

Would you confirm which of these tanks had been turned off?

If it was the header tank the boiler would have auto off due to no water flow. If in was the main water tank I have thought other symptoms such a no water to wc's and no HW anywhere would have being evident.

Check the ball valve in the tank is doing what it should, that it opens and closes when topped up. Check the overflow works by holding down the valve and allowing the tank to overfill (just a tad).

Provided the valve and overflow work, leave it on and the worst that will happen is the overflow will function.

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Cheers Chris.  It's the smaller tank (not my system below but similar) which, as you describe, is controlled with a ball valve.   Everything has been working including central heating until we had an air-lock a week ago.  That's how I discovered it had been shit off.  The smaller tank has an overflow pipe to guess I will leave on?

 

Managed to rid air from the system for all the taps but - despite what I said above - seems the shower cold feed still isn't working.  Any ideas - anyway to test the thermostatic valve in-situ?

 

 

pre-con3-medium.jpg

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The shower, is it a simple mixer of tank stored hot and cold, or via a pump?

Since someone has been fiddling, I try to check along the route of the CW feed from the bigger tank to the shower unit- might there be an isolation valve somewhere that has been fiddled with?

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Here's a diagram of how it all works, try following the feed to the shower.

post-5924-0-54914600-1432377157_thumb.jp

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No pump just a mix of hot and cold feeds. From what I can see there is a pipe from the lower part of the large tank providing the cold feed direct to the shower, a run of about 2 or 3m. Can't see there is much scope for an airlock.

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If it's a shower unit with a braided hose link between the mixer and the shower head might the hose be twisted and deformed to a point where it's constricting the flow?

If it does have a hose take it off and check the output direct out of the mixer.

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It's a concealed unit with a fixed head but, after a bit of messing about the air-lock seems to have gone - think it just needed some time to work everything through.  

 

Thanks for your help.

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The issue last time was a knackered thermostatic valve in the shower which I replaced. Tried the same again this time but no luck :(.

All started when a toilet cistern got jammed open and drained the main tank (ball cock on main tank needs replacing as knackered and not refilling quick enough).

Once main tank refilled we had airlocks which I managed to remove in all the taps. The shower cold feed however remained very weak so I tried to sort by attaching a hose fed by mains pressure. Tried this about 4 times to the point where I couldn't hold any more (with the shower cold feed open) so assumed this would sort any airlock.

The other thing that makes me wonder if it is an airlock is that i think the shower is is on the same feed from the loft as the bath which seems fine (appreciate it splits at some point).

A bit lost as to what to do + not having any luck for recommendations for a local plumber (Bexley if anyone can suggest). I'm reluctant to call out one of the bigger national firms as expect nothing more than a good fleecing!

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What sort of shower is it? Is it a bar one or one with the controls concealed in the wall?

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Yeah, I was hoping it would be a bar one which you could temporarily remove and let the water run through.

Have you checked the filters on the one you have?

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Cheers Daz - thought you might say that. If it's filters on the thermostatic cartridge I've fitted a new one so guessing they are fine.

Does this pic help?

post-6064-0-25094100-1450902274_thumb.jp

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