My open flow rate is 38 litres per minute.

[JonathanM]

That was a fantastic dynamic pressure at that flow rate.

I then disconnected the hose and connected a pressure gauge to it and got 4.5 bar. 4.5 bar isn't fantastic

Presumably that is static pressure.

Does dynamic pressure also need measuring? Or if you get 4.5 bar static, is that basically good enough?

 

[Notch7]

I've become quite conscious of Viessmann in recent days

Urban plumbers has rather mixed views on Viessman: innovative boilers, poor support in the UK

 

[Mr.B]

I did see the Urban Plumbers clip. It wasn't all that reassuring was it. I rather admire the bloke, he seems pretty shrewd.

I can't say if my own measurements are sufficient to warrant fitting s combi and will wait to see what the installer says when he comes.

 

[Johntheo5]

I can't say if my own measurements are sufficient to warrant fitting s combi and will wait to see what the installer says when he comes.

It would be prudent IMO to get both the static & dynamic pressures.
You might try and borrow/buy a PG, install it on the end of that washing machine hose/pipe and open a few cold taps elsewhere in the house to get as big a flow as possible, even 10LPM or less is OK, note the pressures before (static) and after (dynamic) you open the tap(s), this will give you the dP at the measured flow, for example, if the dP is say 1.5bar (4.5/3.0) at a flowrate of 10LPM and if you (think) require a minimum dynamic pressure of 2.0bar, dp of 2.5bar (4.5/2.0) with the shower on upstairs, then the flow will be sqroot (2.5/1.5)*10, 12.9LPM.

 

[Mr.B]

I'm not gonna claim to have fully grasped that in it's entirety but as and when I get hold of a gauge I can take the readings and post them here. The installer that I called who fits WB and Ideal is coming on the 13th of this month. He may have thoughts on the matter. In fact I would be disappointed if he didn't.

 

[Mr.B]

I've ordered a Rothenberger 3/4 BSP pressure gauge with a nice rubber boot round the business end and a WRAS approved braided hose. Bought courtesy of a plumbing shop on Ebay (Stuart Plumbing and Heating in Hinckley).

I've always thought Rothenberg had a decent name so feel confident, and it wasn't a fortune (£15.99 including postage).

It said it was the last one available however I was a bit sceptical, but when I went back to the listing after buying and paying it was showing 'sold out' so I might have actually got the last one - it was the cheapest I spotted online or in Screwfix or Toolstation - the Monument one at S.F. is £30.

It won't get a vast amount of use, and I seem to have managed all these years without one (apart from the one I borrowed from Toolstation a few years ago) but I shan't be found wanting next time I have the need to do a bit of pressure testing via a 3/4 inch washing machine valve.

I'll test the 22mm feed I ran to my proposed combi installation site both statically and dynamically (if I've got that right) and report it back here given that I gratefully received advice from others here recently.