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]

Yes normal as your knocking off 0.3 bar to get the water upto the loft (each floor)

Do you know what your pressures are ?

 

[RS_2022]

Ok thanks. It was 1.1 bar at the mains when we installed the system. Is that too less?

 

[ShaunCorbs]

I’m guessing you tested at the outside tap if you depending on house eg stnd house and now you’ve gone in the loft it’s approximately 0.5 -0.6 bar loss so your down to half a bar in the loft

 

[RS_2022]

Ah I see. What's the best way to solve this? Pressure in the 1st floor bathroom & kitchen (ground floor) is still pretty good. Would a mains booster get the loft up to the same level? Or is there another way to increase pressure up in the loft?

 

[ShaunCorbs]

Depends might be worth a phone call to the water board to see what pressure they can give you in your area

 

[Vee]

A prerequisite of 3 bar and 20 l/min is required generally for any unvented install. If this deviates it will need to be countered. To increase flow bigger pipe, to increase pressure you need to boost. Before deciding what is best get water supplier to measure both at boundary.

 

[RS_2022]

Thank you, that’s so helpful! I have a plumber coming to measure up but he isn’t available until the end of next week so in the interim I’ve tried to conduct my own investigations.

The boiler display shows 1.7 bar water pressure (valiant ecotec hooked up to a joules unvented cylinder).

Thames water said that they provide between 1.5-2 bar water pressure on the street, so it seems like I have the average pressure.

Flow:
It took 7.7 seconds to fill up a one litre measuring can in the kitchen (cold water tap), 3 seconds to fill it up from the outdoor tap and 4.5 seconds to fill up a litre in the loft bathroom (cold water tap - bath).

I believe I have 8.3 litres/minute flow rate in the kitchen, 19-20 litres/minute in the garage and 13.3 litres/minute in the loft. I suspect the tap in the kitchen has a flow restrictor built in.

Inside the flow is less than the 20 litres per minute/ 3 bar guideline you’ve mentioned, but outside I have 20l/minute flow and 1.7 bar pressure.

My logic tells me that means the problem is pressure not flow and with Thames water saying they can only provide upto 2 bar, it would mean changing the pipe work won’t help increase pressure. Does that mean that I could get away with installing a mains booster pump seeing as the flow rate upstairs is not too bad at all?

I want a good strong shower in the loft but I’m also mindful of cost!

Thanks so much!

 

[Ben-gee]

This doesn’t really warrant the “Urgent” banner.
That is for “I’ve got my finger over this pipe, it’s getting hotter, please pass me a stop end”

 

[RS_2022]

Oops, sorry. Didn't realise and I'm a complete newbie so everything sends me into a panic/feels urgent. It isn't letting me edit the banner out now but I'll bear in mind in the future.

 

[RS_2022]

Thank you, that’s so helpful! I have a plumber coming to measure up but he isn’t available until the end of next week so in the interim I’ve tried to conduct my own investigations.

The boiler display shows 1.7 bar water pressure (valiant ecotec hooked up to a joules unvented cylinder).

Thames water said that they provide between 1.5-2 bar water pressure on the street, so it seems like I have the average pressure.

Flow:
It took 7.7 seconds to fill up a one litre measuring can in the kitchen (cold water tap), 3 seconds to fill it up from the outdoor tap and 4.5 seconds to fill up a litre in the loft bathroom (cold water tap - bath).

I believe I have 8.3 litres/minute flow rate in the kitchen, 19-20 litres/minute in the garage and 13.3 litres/minute in the loft. I suspect the tap in the kitchen has a flow restrictor built in.

Inside the flow is less than the 20 litres per minute/ 3 bar guideline you’ve mentioned, but outside I have 20l/minute flow and 1.7 bar pressure.

My logic tells me that means the problem is pressure not flow and with Thames water saying they can only provide upto 2 bar, it would mean changing the pipe work won’t help increase pressure. Does that mean that I could get away with installing a mains booster pump seeing as the flow rate upstairs is not too bad at all?

I want a good strong shower in the loft but I’m also mindful of cost!

Thanks so much!

@ShaunCorbs @Vee I’d appreciate any advice?

 

[ShaunCorbs]

About 20lpm so about right on flow

Correct you will have to install a break tank and booster sorry to say as your issue is pressure that will give you 3 bar or higher depending on what your happy with upstairs

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[John.g]

Just curious as to why the boiler pressure is quoted, except the boiler display can access the mains pressure?
"The boiler display shows 1.7 bar water pressure (valiant ecotec hooked up to a joules unvented cylinder)."

 

[RS_2022]

About 20lpm so about right on flow

Correct you will have to install a break tank and booster sorry to say as your issue is pressure that will give you 3 bar or higher depending on what your happy with upstairs


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Thank you. I’ll look into this!

 

[Vee]

There is a way of reading the flow rate on an Ecotec, but I suspect this was the system pressure which is not relevant to the query. Look at Stuart Turner mainsboost / iBoost , Mainsboost iBoost | Stuart Turner - https://www.stuart-turner.co.uk/our-products/mainsboost/mainsboost-iboost, it’s is a combined one with tank and pump all in one. It works well, installed a couple with great success.