HOW TO INCREASE FLOW RATE & PRESSURE 3 BED SEMI

[AnthonyRad]

Hi all

I have a 3 bed semi work in progress at the moment. It's fed off of a 15mm incoming copper water mains pipe which then branches off in 15mm pipe to feed the bathrooms, boiler, kitchen etc. It already has a Worcester Greenstar 28i Junior in good nick on the 1st floor landing cupboard, a small downstairs loo (basin&toilet) and 1st floor bathroom with a thermostatic mixer.

I’m planning to convert the loft and install an en-suite with an electric shower so as to not overload the boiler…. What do I need to do to increase the water pressure/flowrate to the loft en-suite so that the 2 showers can be on at the same time comfortably? Flow rate and static dynamic pressure results below which I think are quite low:

Flow rate test:
12litre bucket at kitchen sink took 46 seconds to fill.
12/0.77 = 15.58 litres per minute

Static pressure - 2.7 bar
Dynamic pressure - 1 bar

Or is it just a case of changing the boiler, if so to what?

Thanks in advance

 

[NewStart]

Most showers need about 10-12L/min to operate.

The amount of power your boiler needs depends on the temperature change required and the flow rate.

If water enters your home at 5C (winter) and you want a shower at 45C you need to raise the temperature by 40C.

A temp rise of 40C @ 10L/m requires a boiler capable of putting 28KW heat energy into the system.

For two showers simultaneously you'd require 56KW, your boiler is rated at 28KW so you'd get half the temperature rise.

If you want to be able to run two showers together you'd need to have an unvented cylinder installed by a G3 competent engineer and a possible a whole house booster pump.

 

[gmartine]

A different boiler won't do it, if you genuinely want simultaneous two shower capacity then you'll need to either upgrade the mains or install a mains pressure boosting system.

 

[Alan Wright]

Most showers do not need 10 to12 litres a minute for a shower.

A good shower by UK standards needs enough water to rinse your hair (6 litres a minute) and enough pressure to create a nice spray pattern and enough pressure to accelerate the water to give that feel of power (3 metres head).

For an electric shower the output will be very limited because they only have low heating capacity but you will need a minimum of 1 bar pressure or it could cut out.

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Many shower mixers work well with as little as 0.1 bars pressure (1 metre head) but in my mind 6 litres a minute and 3 metres heads (0.3 bars), is perfect. A 7.2 KW electric shower, heating water to 30 degrees Centigrade, will give you 3.5 litres a minute. Some consider 4.0 litres a minute […]

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[Scott_D]

First job would be a new full bore stop tap. And retest.
Then ask the water board to check your supply.
Next you can look at the mire expensive solutions.

Have you got space for an a accumulator?
Mir can you get a new main into the property without destroying the drive etc.

 

[AnthonyRad]

A different boiler won't do it, if you genuinely want simultaneous two shower capacity then you'll need to either upgrade the mains or install a mains pressure boosting system.

Thanks, couple q's: Do you recommend a specific mains pressure booster or the size I might need? Can the booster just fit in a kitchen cupboard and if so are they loud?

@scott_d thanks for the suggestion I will put a full bore tap on and retest, I have a garage but would have to route the incoming mains from where it comes into the kitchen over the downstairs loo to garage then back into kitchen where it branches off unless they can fit in kitchen cupoards?

 

[gmartine]

Something under the cupboard with a small store should be able to maintain the improved pressure provided when on the odd occasion both showers (boiler + electric) are being used...

 

[Alan Wright]

My advice is that you should not put in a solution until you know you have a problem.

How do you know just fitting two showers will not work?

The electric showers do not take much water and if they do not then retrofit solutions are there.

 

[gmartine]

The problem is low dynamic pressure which will not be improved by another outlet in the attic.

 

[NewStart]

[/QUOTE]

My advice is that you should not put in a solution until you know you have a problem.

How do you know just fitting two showers will not work?

The electric showers do not take much water and if they do not then retrofit solutions are there.

You'd need to seek advice from a competent electrician before fitting two power showers. The majority of homes in the UK would not be able to supply the electrical demand for two showers at the same time as well as servicing other demand in the property.