I’ve just measured our mains water pressure and it’s 2.2 bar. Is this good, bad or average?

Static or dynamic ..? That is fairly low, what is the flow like..?

Mine is less, but on the outside tap off 15mm pipework near 32mm supply I get around 20l per min so happy with that. 

I'd say 2.2 is average in the places I've been in but may be low compared to other parts of the country. 

6 hours ago, PeterW said:

Static or dynamic ..? That is fairly low, what is the flow like..?

Static pressure. The flow is reasonable. My main concern is water pressure for showers, is it enough for a reasonable shower?

Where is it measured ..? Ground floor tap will be slightly lower than first floor shower but not much. 
 

Most suppliers do high and low pressure heads for showers and they are easily interchangeable so you can get a decent pressure along with flow too. 
 

Is this all off a UVC ..? If you haven’t already done them, pipe the WCs in 10mm off a branch with the outside tap prior to the PRV and then do everything else as balanced off the PRV. Means if someone flushes a loo you won’t get a cold shower. 

9 hours ago, Triassic said:

I’ve just measured our mains water pressure and it’s 2.2 bar. Is this good, bad or average?

 

That's a bit below average. When we did pressure management for UU, we'd set the PRVs to deliver a min of 20-25m head (2.2bar ish) to the highest elevation property in the zone. The minimum set by the regulator is 12m (1.5bar ish).

 

What time of day did you test? There will be a big difference between middle of the night and peak demand times.... I.e. lowest when you want that shower!

is an accumulator an option?

50 minutes ago, dpmiller said:

is an accumulator an option?

It is,.... Is there a formula for sizing one up?

Our water pressure is 3 bar with a flow of 15 litres/min. 
 

We have two bathrooms and were advised to go for a 200l accumulator. That advice changed recently and a 300l accumulator was recommended. I don’t know about any formula, and as nothing had changed in the design of the house I suspect the plumber just stuck a wet finger in the air but I could be wrong on that. I can’t tell you how it performs because it’s been sat around for weeks waiting to be installed. 
 

It is big. 
 

And blue. 
 

4 hours ago, Triassic said:

It is,.... Is there a formula for sizing one up?

Yes and no ..!

 

An accumulator gives you 50% usable storage so a 200 will give you 100 litres, 300 will give you 150 litres etc. 
 

The issue will be when you get two showers running - and it may even depend on the shower itself. If you had 2 showers at 9 litres / min, the accumulator will support the flow rate in RussDLs case of an additional 3 litres / min so will run for circa 30 mins. Up the showers to 12 litres / min and you’re going to be using a 200 litre accumulator in 12 minutes. 
 

This is where bigger is better, but that comes with cost and space requirements. Also, a lot of clients don’t know what they want at the outset of doing design and first fix when it comes to shower specifications so it does have an element of guesswork to it, so unless you spec “I want to support 2 Mira Digital xyz showers and one has body jets” when you’re asking for a design then it is sometimes more art than science. 
 

@Triassic do you know what showers you want and how many at once ..?

My god what's an average pressure here then?

Surely if flow rate is over 20l per m you're unlikely to need anything else unless you have a large family?

22 minutes ago, Oz07 said:

My god what's an average pressure here then?

Surely if flow rate is over 20l per m you're unlikely to need anything else unless you have a large family?

 

I think it varies widely especially in rural settings. 8bar here hence fitting the prv.

11 hours ago, PeterW said:

@Triassic do you know what showers you want and how many at once

Strangely enough the showers were delivered yesterday, I’ll open the box and see if the flow rate is quoted on the paperwork, other than that I’ll ask the supplier and get back to you for further advice.

23 minutes ago, Onoff said:

 

I think it varies widely especially in rural settings. 8bar here hence fitting the prv.

My god. Bet karcher sales are crap round your end 

5 minutes ago, Oz07 said:

My god. Bet karcher sales are crap round your end 

 

Putting a prv on like @Nickfromwales said stopped the dripping taps and ball cocks in the house. I kept the outside tap on the 8bar though.

 

On 19/12/2020 at 13:52, Triassic said:

Static pressure. The flow is reasonable. My main concern is water pressure for showers, is it enough for a reasonable shower?

 

Tricky question as showers are subjective. Some  googling for data...

 

https://waterwise.org.uk/wp-content/uploads/2019/09/United-Utilities_Water-and-Energy-Efficient-Showers_Project-Report.pdf

 

Electric showers (46% of installed showers) have typical flow-rates of 3 to 8 l/min. The flows are inherently low and any modification to the showerhead or flow characteristics could damage the heating unit.  Mixer showers without pumps (38% of installed showers) have typical flow-rates of 5 to 15 l/min. Pumped showers (16% of installed showers) have typical flow-rates of 10 to over 20 l/min.

 

So which type do you prefer? If it was me I'd want at least 10L/min but I'm out of date on the water regulations.⁰)

 

 

 

9 hours ago, Triassic said:

Strangely enough the showers were delivered yesterday, I’ll open the box and see if the flow rate is quoted on the paperwork, other than that I’ll ask the supplier and get back to you for further advice.

 

 It surprisingly difficult to get data. Very few shower makers provide the graphs of flow vs pressure needed to work out how they will perform. They typically just specify a pressure range over which they will "work". 

 

 

 

 

23 hours ago, Triassic said:

Strangely enough the showers were delivered yesterday, I’ll open the box and see if the flow rate is quoted on the paperwork, other than that I’ll ask the supplier and get back to you for further advice.

The flow rate will possibly change (or the temperature change) depending on the temperature difference between the cold, incoming mains, and the temperature you want the shower to deliver.

Knowing the power (kW) will tell you what temperature lift you can get for any given flow rate.

 

4.18 [kJ.kg^-1.K^-1] x kg.s^-1 [flow rate]. (T₁ - T₀) [temperature increase]

 

 

Edited December 21, 20205 yr by SteamyTea

13 minutes ago, SteamyTea said:

The flow rate will possibly change (or the temperature change) depending on the temperature difference between the cold, incoming mains, and the temperature you want the shower to deliver.

Knowing the power (kW) will tell you what temperature lift you can get for any given flow rate.

 

4.18 [kJ.kg^-1.K^-1] x kg.s^-1 [flow rate]. (T₁ - T₀) [temperature increase]

 

 

That is correct for an electric shower but with a UVC or Sunamp the flow rate of hot and cold is constant as it is from a balanced supply control block where hot and cold are equalised. 

19 minutes ago, PeterW said:

That is correct for an electric shower but with a UVC or Sunamp the flow rate of hot and cold is constant as it is from a balanced supply control block where hot and cold are equalised. 

Yes, I assumed it was an electric one. Must have missed it was coming from a UVC.

 

Or use Bernoulli's empirical formula:

P₁ + 1/2 ρv₁² + ρ_gh_₁ = P₂ + 1/2 ρv₂² + ρgh₂

_Where

_{P = Pressure}

v = Volume

ρ = Density

g = Gravity

h = height

 

For a level pipe run, ρ_gh_1 cancels out with ρgh₂

Edited December 21, 20205 yr by SteamyTea

Just to clarify, is the accumulator fitted to the incoming cold, before it split to hot and cold feed?

2 hours ago, Triassic said:

Just to clarify, is the accumulator fitted to the incoming cold, before it split to hot and cold feed?

Yep that's right

 

https://youtu.be/EbwdEtwnTCs