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Shower flow rate advice request for newly installed shower

Postby lukepricephoto » Sat Jan 30, 2021 3:21 pm

Hi, Thought I would come and ask the experts for some advice regarding a new shower installation.. It's perhaps a bit technical but I am an engineer so forgive me !

ok, so I have 24lpm coming into the property restricted to 6bar with a pressure relief valve to protect the Monarch Water softener. This feeds a new Worcester Bosch Greenstar 8000 40kw Combination boiler.

On the current setup I get the following from a hosed shower head with 10mm bore hose. 14LPM at 30degC, 14lpm at 40degC, 14lpm at 45degC.

note that if I set the boiler to 55degC the shower will run continually at these rates.. if I set the boiler to 60degC the boiler short cycles but I can instead run two hot taps in the house at 9lpm each continually.

This suggests to me that the flow to the shower is restricting the boiler rather than the other way around?

My thought is.. if I replumb the feed from the boiler to the shower in 22mm polypipe (insulated) then install a 3 outlet shower valve to feed either a 300mm drench shower or two wall mounted shower heads (eg Grohe clubmaster or crosswater reflex). I could perhaps use both the wall mounted heads at the same time and get a great shower experience with good flow from each...

Q1. should I plumb in 22mm or 15mm? the distance from boiler to shower is approx 10meters pipework. I don't mind waiting a few moments for the cold to disperse before stepping in..

Q2. should I install a 3/4" valve setup eg crosswater or vado, or should I go with a 1/2" valve unit eg Grohe.

Q3. will I get enough flow from the two wall mounted shower heads or will they just be disappointing.

Q4. I assume that running the boiler at 60degC will be both more efficient for the boiler and allow a better flow rate when fixed with the cold flow. with the increased shower flow I should suffer with short cycling.

Does this all sound reasonable or am I over engineering this as usual ??

Many thanks and best wishes to all in these crazy times!
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