shower pressure/flow readings - unvented

[Docb]

Hello All

I am in the process of having a new bathroom fitted in a new extension, and have taken the following readings.

before shower
Cold static 2.7bar, dynamic 2.2bar, flow 30lpm
Hot static 1.5bar, dynamic 1.4bar, flow 30lpm

after thermostatic shower, before head
Cold static 3 bar, dynamic 3bar, flow 10lpm
Hot static 3bar, dynamic 3bar, flow 12lpm.

I have checked these a number of times as i couldnt quite believe that a thermostatic mixer could increase the pressure, particularly on the hot.

I am guessing that the shower is not right for the system? any recomendations?

would the performance of the shower by good with those readings? as i guess i will lose more through the head as well?

for info i have cold static of 3.3bar and dynamic of 2.8bar with 30lpm before the unventred cylinder.

hopefully you can help, all info greatly received.

thanks

Doc

 

[Agile]

I find those figures too good to believe.

Without knowing in total detail how you have made measurements I cannot comment.

Remember water pressure can vary widely at different times of day.

Tony

 

[Docb]

Hello Agile

i took the readings of pressure from a pressure meter purchased online, it is a cheap thing, only a tenner, bought for this purpose only.

I just attached it to the end of the pipe (plastic).

for the flow i used a stop watch on my mobile and a bucket.....

stopped the stopwatch when i got to 10 litres marked on bucket (20 secs).

same process for "after mixer", but before the head, just attached the pipes.
for info the shower is only around 7 mtrs away from the cylinder, all in 22mm copper.
I will try it again tonight, but i did do it 3 times last night, to make sure i was reading it right.

any thoughts on why the shower would increase pressure but reduce the flow so significantly? I am guessing the small bore inside the thermostat is affecting it? would a different mixer increase the output?

thanks again

Doc

 

[MJN]

same process for "after mixer", but before the head, just attached the pipes.

Can you elaborate on exactly what you mean by this?

Doesn't the output of your thermostatic mixer consist of just the one pipe? If so, how are you measuring hot and cold pressures seperately?

Mathew

 

[Docb]

Sorry yes i should have explained, to try and get 2 readings i am turning the mixer temp gauge to full cold and full hot and taking the reading from the one pipe.

Doc

 

[MJN]

That is what is leading to the spurious results. Merely turning the temperature control from one extreme to the other doesn't translate into connecting/disconnecting one supply or the other.

Even the slightest admission of water from a higher pressure input will result in both readings being that same high value.

Mathew

 

[Docb]

Thanks MJN

but what about the drop in flow? is this just something i have to put up with or is there a way to get the good flow rates to the head?

are there mixers that allow more through? The mixer was supplied by the plumber, who gave us a few options, but the options were design rather than performance related.

would prefer to pay a bit more to get the performance than scrimp now and wish i had taken the opportunity?

thanks

Doc

 

[MJN]

Others would be better positioned to make recommendations as to whether there are any differences to be had between makes/types as I've only ever fitted two and they've both been fine.

Certainly your pressure and pre-shower flow rates seem very good so I can only assume that perhaps a particular shower might well be able to exploit these to maximum effect.

Mathew

 

[Docb]

thanks MJN

anybody able to help?

I have re run the pressure etc, no change apart from at 6 the cold pressure increased slightly to 3.5bar static and 3bar dynamic.

it was the same as the first post at 9pm.

Doc

 

[Docb]

Anybody?