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.

 

[RS_2022]

Hello again. I've now had multiple plumbers as well as Thames Water come in and have a look and it's only confused me more.

The pressure at the water meter is 3.5-4bar with a 20l/min flow rate. The pressure at the outside tap is 3-3.5 bar with a 20l/min flow rate. We couldn't get a pressure gauge to fit on any of the inside taps, but the flow rate in the kitchen is between 8 -10l/min and in the loft it's about 13l/min. I have a new Megaflo in the garage and the plumber who installed it has told me that all the pipes coming from the Megaflo are 22mm ones.

I have new plumbing and new Hansgrohe fittings in both the first floor and second-floor bathrooms and the fitter has assured me that all the pipes he's used are also 22mm ones, that connect to 15mm ones just before they connect into the shower/etc.

It seems like the water pressure & flow are both good at the water meter as well as at the outside tap, but both drop significantly inside the house.

I've had a few people suggest I change the mains pipes to 32mm blue pipes, but I don't see how that would help considering the fact that despite the old pipes, the water pressure at my outside tap is excellent.

I've also had plumbers suggest the break tank/booster pump solution but no one can seem to work out what the issue is and therefore the solutions they suggest feel like guesswork.

Has anyone had anything like this before? Any idea why the water flow and pressure is dropping so much and what I could do to fix it?

@Vee @ShaunCorbs ?

 

[ShaunCorbs]

Outlets / taps could be restricted/ have flow limiters

Have you tested from an open pipe ?

 

[RS_2022]

Outlets / taps could be restricted/ have flow limiters

Have you tested from an open pipe ?

Not from an open pipe, no. How do I do that?

I did check and the Hansgrohe products all seem to have a max flow rate of 15-17l/minute. Have I just spent a fortune on products that reduce flow/pressure?!

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[ShaunCorbs]

Would suggest getting a plumber in to test from the loft bathroom both hot and cold flow rates from an unregulated source eg straight off a 15mm pipe to a basin etc

 

[RS_2022]

Would suggest getting a plumber in to test from the loft bathroom both hot and cold flow rates from an unregulated source eg straight off a 15mm pipe to a basin etc

Okay, I'll do that and report back. Thanks so much.

What would be a good flow rate and pressure in this situation? The house has 3 bar & 20l/min at the outside tap, the system is an unvented Megaflo installed 6 months ago and I have 2 bathrooms - 1st floor & 2nd floor (loft).

 

[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