2 Cold Water Feeds to the House Wrecking Havoc with Hot Water

[BillyWillySilly]

I've had trouble for a while now with my pump not kicking in for the hot water. I was advised to change it as the only remediation other than pulling up tiles so thought it was worth a shot.
So I changed the pump to a Salamander 3 bar CT Regenerative pump and if anything it's worse. Certainly noisier! I thought these things were supposed to be quiet?! When the pump does kick in I can tell it's more powerful but it still needs to be triggered by another tap further down the system, again.

So I began to do some testing:
When I turn on the shower (closest to the pump/tank) this results in no pump.
Then I turn on the hot water tap in the bathroom. This makes the pump kick in.
If I then turn off the bath tap, the pump stays on. So there's something about the level of pressure to trigger the pump.

Now, I then started to go back down the system switching on taps, etc to the kitchen where we have an additional stop cock. Apparently, many years ago my house was divided into two and an electrician noted that he found another stop cock under a kitchen plinth. And recently we had new tap cartridges fitted in the kitchen and it was noted that even when the hot water was off, there was still a trickle of water running. What a previous plumber thought was an anti-scold valve causing the cold water in the hot feed, I now think is this secondary cold feed.

I turned this off and low and behold the pump kicks in for every hot tap as clockwork. However, it also kicks in for cold feeds on certain taps only on one side of the house. I cannot be certain but I think that when the hot water was plumbed, the cold feeds were not unified, and somewhere they are merging. Also, the pressure is borderline unusable on one side of the house.

So I'm between a rock and a hard place. Either we have the hot water working to plan with poor cold water feed to some parts of the house (including the pump kicking in when the toilet is flushed!) or revert to the former. I cannot find a sweet spot on the cold water feed to balance it - it's either fine for downstairs or not for upstairs etc or doesn't trigger the hot water.

And I'm not sure what help I'm expecting from this forum as I'm pretty sure someone will say "get the house re-plumbed". Which is not feasible right now.

 

[terryplumb]

If mains cold water is entering your domestic hot water pipework ,the level of water in your cold water storage tank in the loft would very likely rise to overflow level ,and water would flow from the overflow pipe externally. Does it ??
From what you have explained ,it appears that certain taps / shower valves ,when turned on ,do not trigger the pump ,but others do. Is that consistently the case with each one ,or does it vary ?

 

[BillyWillySilly]

It is consistent dependant on the flow of the second stopcock (although I am tweaking an isolator valve that is under the sink. At the moment, I have it set so that the downstairs tap cold doesn't trigger the pump, but upstairs, it does. The shower needs to force the pump on - so turn the shower on, then a tap, the pump kicks in, and then the tap can be turned off.

If this is full on, the only way to trigger the hot water pump to kick in is to run that bath and the shower at the same time.

There is no overflow as far as I can tell.

 

[CBW]

I’m wondering if the pipework has been crossed at some point?

 

[BillyWillySilly]

I’m wondering if the pipework has been crossed at some point?

I think so. I have to expose the floor for some electrical work so I reckon I'll have to go searching.

 

[mattylad]

Have you tried turning 1 stopcock off (alternately) to see the effect?

 

[BillyWillySilly]

Have you tried turning 1 stopcock off (alternately) to see the effect?

Yes, and the hot water feeds also. When I turn off the cold and hot water on one side of the house, cold taps stop completely but I still get a trickle from hot. I first panicked and thought there was a leak somewhere but we would have noticed by now.

When I do the inverse, and cold from the other side, the variability of the feed introduces these issues. I think most of the pipes are accessible but I just have to move the heaped piles of kids and furniture first!