Water-tank overflowing & odd plumbing ! Comments please ?

[Adrian]

HI All

Finally got round to looking at why we're getting a slight dribble of an overflow from the cold tanks in the loft.

(It tends to only be noticeable last thing at night when I put the dogs 'out' - so by the following morning it's long forgotten - been like that for a few months !)

Anyway - just seeking a 'reality check' from you good people... please take a quick look at

gives a photo of the installation and describes the problem.

I guess a really slow leak on the c/h header tank ball valve is the most likely culprit...... but it 'seemed' to be sealing OK when I had a quick look yesterday.

More puzzling (to me!) is the strange arrangement with the 'hairpin' overflow pipe - don't quite see what this pipe achieves that the other connection to the base of the c/h header tank doesn't ?

FWIW - the heating system 'downstream' of this is run from a ground-source heatpump - with two circulating pumps for dhw and c/h.

Thanks in advance for any comments

Adrian

[Geo]

Um - I will leave it to the experts - but it I would not have done it like that. How about a trickle from the overflow of the upper tank running back into the lower tank via its overflow (and the T). I may get shot down shortly - but the CH vent pipe looks like a bodge - when was this lot installed?

Geo

[Adrian]

Hi Geo

Thanks for the comments.....

Not sure I would have either ! - which is why I was asking...

I guess it's possible - but it'd need more than a trickle as the water 'wants' to continue flowing down the overflow and would tend to bypass the 'T' into the lower tank.

The level in the top tank is fine... Mind - the pivot pin in the top tank ball valve fell into two bits when I tried to remove it - totally corroded through.

We have fairly (!!) acidic well-water here - which is now treated by chemical injection/mixing at the wellhead... - which results in about pH7 at the taps.

About 2 - 3 years ago - and not by me, I hasten to add !

Regards Adrian

[Sparks]

Do you have a hot water cylinder too somewhere?

If so, is there a vent pipe from this, overhanging one of the tanks?

[Roger Mills]

The most likely cause of your problem is a leak in the indirect coil inside the hot water cylinder - allowing water from the primary and secondary circuits to mix - which they ain't supposed to do. Because the level in the cold water header tank is higher than that in the CH F&E tank, the static pressure in the secondary system is higher than that in the primary system, with the result that secondary water leaks *into* the coil - and thence into the F&E tank. Sounds like it's time for a new HW cylinder - which may well enable you to get one which is much better insulated and which has a larger internal heat exchanger (providing faster recovery) than the old one.

Your connections to the F&E tank are 'unusual'! You should have separate fill and vent pipes all the way (or very close) to where they join into the main flow pipes. Otherwise, it's very difficult to fill the system - 'cos water needs to go down the fill pipe and the displaced air needs to come up the vent pipe. Also, the vent pipe is a safety device to release steam in case a problem with the boiler causes it to actually boil. [Probably less of a problem with a boiler-less heat-pump system].

[Adrian]

OH yes !

OH Yes ! (sounds like that darned dog on the insurance ad!)

You can just about see it in the photo - tan-coloured pipe that finds its way up to the big cold-water tank.

Regards Adrian

[Sparks]

Then it could be, as someone else has pointed out, water getting into the central heating circuit from a leaking coil in the hot water tank.

It is impossible to tell right now, so we need to work it out by elimination! You need to turn off the water supply to the small header tank, so see if this stops the water rising.

As you don't appear to have a stop-c*ck between the mains water pipe and the small tank, my suggestion is to turn off you main stop-c*ck before you go to bed tonight, go up and bale out some water from the small tank, then see if it has risen in the morning. If it has, then it has to be getting in via the hot cylinder, if not, then the ball-c*ck bust be dripping!

[The Medway Handyman]

I'd guess at a slow drip from the ball valve in the CH tank. Ball valves quite often seem OK when manually lifted, but can drip when slowly closed by the water pressure. Having said that, overflows are usually at their worst in the mornings - after a night of no water use & slow drips.

Cheap enough to DIY change the ball valve & see.

Its an expansion pipe & has to have an air gap between it & the water.

[Sparks]

Just to add, I would also turn on the cold water tap in the Kitchen (and leave it on), just in case you don't turn off the main stop-c*ck 100%!

We don't want to see a false positive, and then you ending up changing the cylinder and still having the problem!

[Adrian]

Thanks for the comments - appreciated.

Well - I think I can rule out the leaky cylinder theory (certainly hope I can !!)

Reason being - the dripping was noticeable way back in the Spring of last year - before we had the heat pump commissioned. As part of the commissioning process we discovered that the original hot water tank had a heat-exchanger coil that was way too small for the heat pump - so we had a brand new cylinder fitted....

I'm hoping that it's very unlikely that both the original cylinder and the new (6 months old) cylinder both have coil-to-cylinder leaks !

I guess that only leaves the stopcock as a possible culprit - after all - the water has to be coming from 'somewhere' !??

Turning off the supply to the stopcock isn't quite that simple..... in fact - it wouldn't be a bad idea to have a stopcock in the loft just to isolate both ball-valves. Our 'mains' cold water comes from our own deep-bore well, with an electric pump and a pressure vessel - and turning it 'off' involves going out in the dark, rain, wind and cold..... which I'm not about to do tonight !

Maybe the best plan is to buy me one of those nice full-bore lever valves to isolate the tank supply with - and a new ballvalve for good measure. If I fit the two of them and still get the header tank filling up then I'll start to believe that it's the cylinder

All of this will have to wait until life returns to normal out here - and 'useful shops' reopen - which may take until 2nd January...

Many thanks for the comments

Adrian West Cork, Ireland

[Adrian]

Yes - maybe you're right after all.... Need to go shopping for spare bits then - this part of Ireland doesn't seem to wake up (or sober up ) until after New Year - so won't be able to test the theory until then...

Hmm - yes - but I don't see what difference there is between the copper hairpin and the other (plastic) connection to the base of the header tank.....

Anyway - If I can stop it from dripping then I'll not worry too much !

Thanks!

Adrian