Cold Water Supply Isolation.

[Hysteresis]

I needed to replace a hot and cold taps in my bathroom, As there was no local isolation valves for these taps, it was necessary for me to Isolate the Cold water supply tap, and as a precaution I also Isolated the supply entering my Hot Water cylinder. There was a very odd result to this Isolation which was that two Cold water taps did not isolate completely. I assumed that there was residual pressure in the cold water piping so I opened several cold water taps around the house. Most successfully Isolated, but two on the ground floor reduced flow to about 10% of full flow. I let them drain for maybe an hour but two taps continued to discharge cold water maybe 5% full flow. All other taps isolated as expected. I cannot understand how, after isolation of the cold supply to my house that two cold water taps continued to discharge cold water. Just where the source of this cold water remains a mystery to me.
As all upstairs tap did successfully isolate, I went ahead with the job in hand, after which I opened the supply Isolation valve so Job Done.
The question is, Has anyone any idea why ONLY two cold water taps continued to discharge cold water even when the supply isolation valve was fully closed. The Supply isolation valve was confirmed as being fully closed because all other cold water taps on the system when opened, did not discharge any water.

 

[endecotp]

Your main valve is passing; it only comes out of those taps because they are closest or lowest.

 

[foxhole]

I needed to replace a hot and cold taps in my bathroom, As there was no local isolation valves for these taps, it was necessary for me to Isolate the Cold water supply tap, and as a precaution I also Isolated the supply entering my Hot Water cylinder. There was a very odd result to this Isolation which was that two Cold water taps did not isolate completely. I assumed that there was residual pressure in the cold water piping so I opened several cold water taps around the house. Most successfully Isolated, but two on the ground floor reduced flow to about 10% of full flow. I let them drain for maybe an hour but two taps continued to discharge cold water maybe 5% full flow. All other taps isolated as expected. I cannot understand how, after isolation of the cold supply to my house that two cold water taps continued to discharge cold water. Just where the source of this cold water remains a mystery to me.
As all upstairs tap did successfully isolate, I went ahead with the job in hand, after which I opened the supply Isolation valve so Job Done.
The question is, Has anyone any idea why ONLY two cold water taps continued to discharge cold water even when the supply isolation valve was fully closed. The Supply isolation valve was confirmed as being fully closed because all other cold water taps on the system when opened, did not discharge any water.

So you have a cold water tank?

 

[Hysteresis]

Hi Foxhole, Thanks so much for your reply. I should have mentioned the CH/Hot Water System is a closed sealed system manufactured by Gledhill - Accolade. It was installed when my house was built 25 years ago and apart from a few age related issues, has operated admirably.
The isolation to which I refer produced unexplained characteristics to my simple mind. Most taps throughout the house were water flow free, but two taps which were positioned the closest to the main isolation valve partially discharge water even after an Hour of attempted draining. It only effected the Cold water taps. I am at a loss to understand or explain this continued very reduced flow rate. It would be a problem if ever I have to replace either of these taps as I would have to do it with water leaking all over the place. I am so Puzzled.

 

[foxhole]

Isolate incoming main supply?

 

[Hysteresis]

Hi Foxhole

Isolate incoming main supply?

Thereby hangs a dilemma!! I think you are spot on, the taps closest to the isolation valves were the ones passing water. In doing so stopped pressure getting to the other taps on the system. If the primary isolation valve is passing then how can that tap be changed? As it is inside my property I assume it is not a water company responsibility to replace it. In order to replace it I would have to close the water companies isolation valve, and assume that would be the water companies responsibility. I have no idea where the water companies Isolation valve is, I can't locate it at the water meter point, so I will have to talk to the water company. Thanks so much for your identification of the problem. Your help was invaluable, Thanks Again,

 

[foxhole]

Isolation is at the water meter. You don’t need the water company you can do it yourself.

 

[Hysteresis]

Thanks so much Foxhole, I had a look at my Meter and there it was, the isolation valve you identified. What I noticed was that the cylinder in which the water meter is located (which is Identical to your picture) is Full of water almost to the Access Cover . Clearly I have no idea if this is storm water or a leak on the water company pipework, I will report it to the Water company and see their reaction.
Thanks so much for your Help Foxhole, There is isolation valve of which I was never aware of its existence. I can now set about replacing the Isolation valve inside of my home. Thanks again, you are a STAR.