Pressure loss in new loft (unvented cylinder)

[RS_2022]

Hello. I need some urgent advice re water pressure in an unvented system.

A few months back, I had my gravity fed system + boiler changed to an unvented cylinder + system boiler. The water pressure following the swap was incredible. We were originally talking about putting in a mains booster pump but seeing how good the pressure was without it, the plumber suggested we skip that step. He changed the incoming mains pipe within the property to 22mm and we left it at that. No digging, no moles, no blue pipe replacement or mains booster pumps.

Fast forward a few months. I’ve just had a loft conversion and water pressure in the loft bathroom is nowhere near what I have downstairs. The fitter has told me he used 22mm pipes up to a point but then changed to 15mm as that’s what’s needed to attach to showers and such. The fitter is saying the poor pressure is a result of not changing to blue pipes when we installed the unvented system and that a mains booster is pointless in this scenario. The original plumber says a mains booster might do the trick but a pump being a mechanical thing is more prone to faults so changing to blue pipes would be better long term but also much more intrusive and expensive.

I’m totally confused as to what to do and I have a few questions -

1. Is it normal for water pressure to drop in the loft despite having a new unvented system? The house has gone from having 1 bathroom to 2, pressure in the kitchen is still incredible.

2. Is there something my fitter’s overlooked that might be causing the problem with the pressure loss, such as pipe sizes or valves or some other technical aspect for example?

3. What is the best solution here? I’m tempted by the mains booster solution as it sounds like an easy, quick fix with no disruption to my drive but is it false economy?

Any help and advice would be much much appreciated! Thank you.

 

[ShaunCorbs]

Ideally you should still have 20lpm upstairs but let’s say 2 bar 15lpm is ok in the loft

 

[RS_2022]

All checked.

Ideally you should still have 20lpm upstairs but let’s say 2 bar 15lpm is ok in the loft

Ok so I've now checked -

Pressure at water meter - 3.5-4bar
Flow rate at water meter - 20lpm

Pressure outside tap - 3-3.5bar
Dynamic pressure outside tap - 2.5-3 bar
Flow rate outside tap - 20lpm

Pressure in 1st floor bathroom - 2.5 bar

Pressure in loft - 2.2bar
Flow rate in loft - 13 lpm (from a shower hose without the showerhead)

The flow rate seems to be dropping quite considerably from the outside tap to the 2nd floor, but I think pressure's probably okay..?

What do you think?

 

[ShaunCorbs]

They look just about there depends how much of a good shower you want

If your happy with first floor bathroom shower then you shouldn’t notice any difference

But if you do like a good shower only way is to control the water pressure yourself eg dab pump in my above link you can set it to 4 bar etc providing the issue is just your incoming mains water

 

[RS_2022]

They look just about there depends how much of a good shower you want

If your happy with first floor bathroom shower then you shouldn’t notice any difference

But if you do like a good shower only way is to control the water pressure yourself eg dab pump in my above link you can set it to 4 bar etc providing the issue is just your incoming mains water

Thank you. I do want a good, strong shower. Do you think installing a pump will be more effective than a mains pipe replacement in this scenario?

 

[ShaunCorbs]

It all depends on what the water supplier can give you, you already have a good supply I doubt your loosing / they can increase it by replacing the mains

 

[Ben-gee]

With a lot of showers being “eco’d” to 9lpm I would have thought 13 acceptable to any planet loving grown-up.

Seriously though, have you tried a proper air incorporating shower head, like Hansgrohe raindance etc? You’ll be surprised at the perceived differences…

 

[Timmy D]

Could be debris in the loft shower inlet filters