Hot water problem after fitting new taps


Postby sheffman » Tue Sep 09, 2008 2:43 pm

I have just fitted replacement basin taps in my son's house (built 12 years ago). besides isolating the cold water at the stopcock i also had to drain down the hot water cylinder as there was no isolating valve on the hot water take off line, and I also couldn't close the valve from the expansion tank to the hot water cylinger as it was seized open....I just knew if i forced it it would have sheared. All went well, until I opened up the stopcock to fill up the expansion tank and hot water cylinder and supply the cold water system. The hot water ran but then stopped...I thought about possible air locks somewe=here so opend up all hot water taps and using the bath mixer blocked off used the cold water at mains pressure to force any air out of the hot water system...however, hot water still didnt flow. On examination of the expansion tank in the loft i found the water supply no more than a slight flow from the ballcock...therefore accounting for no hot water flow through the taps as the expansion tank had no more than a covering of the base, and will take an age to fill. The same flow was seen through the ballcock in the central heating header tank which is fed through the same line, so i know it's unlikely to be the ballcock valve that is faulty. I noted that both lines had inline isolating ball valves and am wondering if it is the prescence of these in a 15mm feed pipe that is causing the low flow rate and therefore if I am stuck with the problem, accepting that it's infrequent that both the hot water cylinder and exopansion tank would be drained in normal use. Anyone any suggestions/advice?
thanks
sheffman
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Postby nitro23456 » Tue Sep 09, 2008 3:47 pm

ballofix valves don't effect the flow of water (unless they are partially/closed of course!).

For future reference, if the CW storage tank is empty and the water supply to it is off, you do not need to drain the cylinder as there will be no 'head' of water to push the hot out of the cylinder. SO in short you could have turned off mains and drained the CW loft tank only (or even bunged it to save draining it), run taps until they stop.

Why was there any flow through the F&E heating tank? this tank is unrelated and a trickle into this tank is all you should possibly have seen if anything upon reinstation of the mains.

Sounds like the mains hasnt been turned back on properly (seized stopcock)..... check mains pressure is OK at kitchen tap to diagnose/rule out.

OR the inlet valve to the header tank is gunged up with crud (hence slow flow inwards)....... however, once it is eventually full, did the hot water supply return to the taps? (albeit probably cold?) If so, you dont have an airlock and it is the lack of head pressure caused by the incorrectly filling/empty CW tank meaning the hot can't be pushed out the cylinder

Solution..... new inlet valve to the header tank (£5ish) or dismantle and clean the exisitng one (still may not work)
nitro23456
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Postby nitro23456 » Tue Sep 09, 2008 3:49 pm

ballofix valves don't effect the flow of water (unless they are partially/closed of course!).

For future reference, if the CW storage tank is empty and the water supply to it is off, you do not need to drain the cylinder as there will be no 'head' of water to push the hot out of the cylinder. SO in short you could have turned off mains and drained the CW loft tank only (or even bunged it to save draining it), run taps until they stop.

Why was there any flow through the F&E heating tank? this tank is unrelated and a trickle into this tank is all you should possibly have seen if anything upon reinstation of the mains.

Sounds like the mains hasnt been turned back on properly (seized stopcock)..... check mains pressure is OK at kitchen tap to diagnose/rule out.

OR the inlet valve to the header tank is gunged up with crud (hence slow flow inwards)....... however, once it is eventually full, did the hot water supply return to the taps? (albeit probably cold?) If so, you dont have an airlock and it is the lack of head pressure caused by the incorrectly filling/empty CW tank meaning the hot can't be pushed out the cylinder

Solution..... new inlet valve to the header tank (£5ish) or dismantle and clean the exisitng one (still may not work)

Also if all other hot taps are OK but not the new ones... you have bought taps for a mains pressure system ie combi boiler and not suitable for gravity fed systems.
nitro23456
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Joined: Sun Aug 12, 2007 6:19 pm


Postby htg engineer » Tue Sep 09, 2008 8:43 pm

I bet it's the ball valve to blame.

Check isolation valves are fully open - if so, crack open nut before ballvalve - good pressure ? ball valve at fault.

You didn't drain the heating side, so why was the heating F&E refilling ? was the heating tank full and thats why there was a trickle of water

Once you get the tank refilling properly the hot water flow should return to normal.

htg
htg engineer
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Postby sheffman » Tue Sep 09, 2008 9:28 pm

Sorry I didn't make it clear, the C/H wasn't refilling because as you say i hadnt drained it, but i did depress the ball cock in the c/h expansion tank to check the flow out of that valve and it appeared to be the same as that through the ballcock valve for the cold water tank, so I assumed that the chances of both ballcocks being faulty were slim...however, i suppose it is possible...so thanks for the suggestion and ill crack the nut before the valve and see if that throws any light on it.
sheffman
Posts: 2
Joined: Wed Apr 16, 2008 8:14 am


Postby TheDoctor4 » Wed Oct 16, 2013 11:03 am

Some great responses here, thx everyone. For any viewers looking for more info on similar issues please see our DIY Projects category for taps and valves which covers tap installation and repair, ceramic disc taps, speedfit plumbing fittings, connecting taps and more.
TheDoctor4
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Location: Somerset in the UK in Shepton mallet


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