Had it all checked by a different plumber to that who installed who reckons we've got 2.8 bar and only 28 l/min coming out the megaflow which is then 2.5 bar and 22 l/min once the other side of the 2 shower mixers.
I'd say that's absolutely normal. That's what I've measured, give or take, most often.
The valves are quite restrictive which will lose you some pressure from the 3.x set on the inlet valve. Ordinary house plumbing is perfectly likely to restrict the flow to 22l/min.
The WB would have restricted the flow, unless it was restricted elsewhere. In your case it was probably restricted at the shower head by small holes. With 4 bar , you would have got very fast water flow, which feels good. A bucket tipped over your head is a hell of a flow rate, but doesn't feel the same. That's how electric showers feel halfway reasonable, with a measly 4l/min flow rate.
Your flow and pressure DO sound adequate for an "exhilarating showering experience" but you WILL HAVE TO match the head to give what you want.
I have to say i used to have an exhilarating shower experience with the 14/5 year old combi but the moment the megaflow went in, that experience went out! Perhaps I got used to what we had before and newer is worse as in many things in life
The later Megaflo inlet valves are less restrictive, so you could look at what you've got. Much of your resistance will be pipework though - it all has to be 22mm or larger for best results if it's any length - more than a couple of metres. Check your shower hose internal diameter is as big as poss, which means 13mm.
See below - I am beginning to think it's far more likely to be pressure than flow rate. I have separate 22mm all the way to the shower mixer (about 4m including the vertical runs down from the top of the megaflow under the floor 2m then up to the i-Box Hansgrohe mixer). I then have 15mm from the mixer to a fixed Hansgrohe raindance head and 15mm to an outlet with hose (don't know the bore) to a normal size head on a bar. I had a Hansgrohe raindance head at my last house run off a 3 bar Stuart Turner monsoon pump so know what they are capable of.
I use a 4.5 bar pump and not a particularly high flow rate, but the jets are fast and feel nice.
Wish i had big time!
WHen I install unvented cylinders I usually put pressure gauges on the inlet and the outlet. They cost just a few quid but answer everyone's questions. Very often you'll find an enormous drop across a shower mixer, such as a Grohe.
Great idea and something I should get done - where in London are you based if you fancy the job?
I'm concerned about WHERE the inlet pressure/flow was measured. I wouldn't be surpriised if 4 bar in the road, with NO flow, became MUCH less than 3 bar with 20 litres/minute flow, at the inlet to the unvented cylinder.
As per earlier posting "To be exact Thames Water measured the pressure and flow rate at the meter just outside our boundary as 4.2 bar and 40 l/min - this was after new mains was installed in our street and new bigger bore blue pipe from the mains to the meter. At the same time as they were digging it all up I had the blue pipe extended onto my land and joined to the old lead pipe leading into our house ready for the refurb works. In this form the pressure was measured as 4.0 bar and flow rate still 40 l/min at an inside tap fed directly off the incoming mains despite the lead and 15mm pipework restriction which surprised me - they provided certificate stating this and did have quite a fancy flow rate measuring device rather than a glorified cup."
It might sound haughty, but very very few plumbers fully understand dynamic/static pressures and flows and speeds and volumes...
You have to measure the pressure at several points along the route with the water going out of the shower (not disconnected halfway
) to find how big the resistances are.
