DIY Doctor

Cold Water Storage Tank very slow to fill

Postby hulldj » Mon Jun 30, 2008 8:58 pm

Hi all,

This is my first post, so please bear with me, and thanks in advance for any help.

I have just moved house and i'm having problems in the new property.
the rising main feed to my cold water storage tank seems to have no real preassure, it seems to only refill at the same rate you would expect from a tap being turned on about a quarter of a turn. consequently when running a bath or taking a shower, the hot water and cold reduce to a trickle when the CWST becomes empty. I currently have to run as much hot as i can get out of the tank, then keep running up and down the stairs with pans of cold water from the downstairs taps to cool it enough to get into! I have timed the refill of the hot water cylinder and CWST and it takes about 40 mins to complete.

The rising main enters the loft with what i beleive is a 15mm pipe, it runs into a service valve and then is 'T'd off to the CWST and the CH Expansion tank, the flow rate is the same at both tanks so I know the flow rate/preassure problem is not to do with the ball valve oni the tank.
Is it possible for the service valve to be faulty, causing a lack of preassure? and if so is it easy to diagnose these faults? the rushing sound of water does seem to be loud around the valve.

If this is not the case can anyone please advise where my next point of diagnosis should start, water preassure and flow from the kitchen tap, although not outstanding is not a problem.

Thanks in advance
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Simply Build It

Postby EyeTry » Tue Jul 01, 2008 9:56 am

The start of your cold water supply is the water company`s stop cock / water meter at the boundary of your property. The next check point is the stop cock (usually in kitchen) so turn your kitchen cold tap on gradually and see how much pressure there is - i.e. would fill the sink eventually or it hits the sink so hard it splashes everywhere. The supply from that stop cock to the CWST is the "rising main" (as you`ve already said) and so relies on the degree of opening of the stop cock for the pressure to the ball valve. Bear in mind that pressure has to push a weight of water UP that rising main (20 feet plus?) through any bends and twists in the run of pipe AND against the closing effect of the ball valve. So open the stop cock a half or one turn - then check the result at your CWST - and again as necessary.

If that has no effect you have to move to the next check-point. As you have a service valve I`m assuming it is the in-line type with a handle or slot-type head that is open with the slot in line with the pipe, and closed when the slot is across the line of the pipe. That uses a close fitting "ball" with a hole through it, now you see it, now you don`t. They last a long time but SV`s are cheap and easily replaced if suspect. However if it is a fitting that uses a washer then it is possible that has perished and is reduced the bore / flow. You would have that fully open as it is the ball valve that dictates the flow to the respective tanks.

One last thought - it`s not the other half`s way of getting a fitness regime in place for the holidays - the running up and downstairs with pans of cold water....

Good luck, EyeTry
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Postby bobplum » Tue Jul 01, 2008 6:28 pm

firstly is the gate valve fully open,if so it is possibly damaged in someway
turn the water off from the internel stop valve,usually under the sink and replace valve see how it goes from there
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