Shower pressure after UVC install

[elvis80]

Hi everyone - this is only my second thread on here, so I hope I'm observing all the rules...would appreciate your thoughts...

We're in the middle of rebuilding a house and going from this system...:
- 2 x bathrooms, relying on a gas combi and mains water pressure @ 6.5 barr, 1/2 inch main to the house and 15mm water pipes
...to this one:
- 4 x bathrooms (only one running as yet), system boiler, UVC and a limiter @ 3.5 barr. 22mm hot water loop (copper), 20mm (pex-al-pex) cold loop. 32mm main to the house. We have a low-loss header - whatever that is...
We have a 1/2 inch BSP manifold in each bathroom, which spurs off to16mm pex-al-pex to each set of taps (shower / basin / bath) and the loo. Those 16mm are never very long runs.

Since doing all this at great expense (using a professional plumber, in whom I'm v confident - friend and v highly rated locally), I've noticed a significant drop in hot water pressure - especially in the shower. Before we start putting up too many walls etc, I want to make sure of the reason...

- At the moment, we have a very cheap set of thermostatic bathtaps, with a shower diverter in the one functioning bathroom. (Ultimately, I've some pretty decent in-wall Bristan shower values, that I haven't yet installed.) The pressure is poor through these cheap taps and their shower valve. The cold pressure is significantly better - but not great. My builder thinks it might be the cheap/rubbish tap having a small bore internally for the hot - in leiu of a proper thermostatic value. The hot water pressure in the bathroom mixer tap on the basin appears to be slightly better than the hot water pressure in the shower (although not sure it's as good as the cold in the basin). My plumber's perspective is we'll inevitably have less pressure that we did previously - he's back in April, but I want to make sure I'm prepared to ask the right questions and have some pressure stats to compare, so we can isolate the issue. I'm keen to find out how / why there's a difference between the hot and the cold pressures, and compare the pressures (and/or flow rate) of each (shower vs basin / hot vs cold.). Is there an inexpensive way of doing the latter?

 

[Scott_D]

is It balanced hot and cold supplies from the combination valve at the cylinder?

 

[elvis80]

is It balanced hot and cold supplies from the combination valve at the cylinder?

Thanks for the reply. Not 100% sure, but I don't believe so. Cold comes into the house, to the water softener and then into the cold loop, I'm pretty sure. Assuming that makes it c.3.5bar, that's what's making me think something is wrong. The UVC should be pumping out 3.5bar, if that's what it's regulated to, but the hot and cold pressure don't compare - even on the kitchen sink, which is on a separate manifold to the shower. The shower is the worst though.

 

[Scott_D]

Thanks for the reply. Not 100% sure, but I don't believe so. Cold comes into the house, to the water softener and then into the cold loop, I'm pretty sure. Assuming that makes it c.3.5bar, that's what's making me think something is wrong. The UVC should be pumping out 3.5bar, if that's what it's regulated to, but the hot and cold pressure don't compare - even on the kitchen sink, which is on a separate manifold to the shower. The shower is the worst though.

Can you post some pictures?
The new main could have dragged in some dirt and blocked a filter

 

[elvis80]

Can you post some pictures?
The new main could have dragged in some dirt and blocked a filter

Thanks. Will do. It's all rather heavily lagged though. I fitted the main myself, it's possible. A filter in the UVC, you mean? I'll see what I've got on my phone.

 

[Scott_D]

Thanks. Will do. It's all rather heavily lagged though. I fitted the main myself, it's possible. A filter in the UVC, you mean? I'll see what I've got on my phone.

Yes, that might explain the hot poor - cold good symptons.
Ideally you would have balanced hot and cold supplies to mixer taps and showers though.

 

[elvis80]

This was taken before we replaced the main.

 

[elvis80]

Yes, that might explain the hot poor - cold good symptons.
Ideally you would have balanced hot and cold supplies to mixer taps and showers though.

Does the pic answer the balanced question? Again, appreciate your help/replies. I've a lot of trust in my plumber. I just want to be able to better inform myself, ahead of his return in April, so we can nail the problem.

 

[Scott_D]

Its a bit difficult to see what goes where from that picture.
Im guessing some of its temporary but its a bit of a mess.

 

[elvis80]

Its a bit difficult to see what goes where from that picture.
Im guessing some of its temporary but its a bit of a mess.

Yes, quite a bit of temporary, as this was pre-lagging. Here are some more.

 

[Scott_D]

Looks like you have balanced cold and hot as there is a PRV going up and the prv for the cold supply to the cylinder (if they are set at the same pressure)

 

[Riley]

What was the incoming pressure and flow?? Assuming this was measured prior to install