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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> Shower problem. https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1316005844 Message started by m on Sep 14^th, 2011, 2:10pm

Title: Shower problem.
Post by m on Sep 14^th, 2011, 2:10pm

Hi all, I have just fitted a thermastat controlled mixer shower to my bath. However, when running the water it pulsates and wont run as a continuous spray, although the temperature stays constant. Any idea why? Thanks M.

Title: Re: Shower problem.
Post by m on Sep 14^th, 2011, 4:24pm

Perhaps I should add, we have an immersion heater and mains cold feed. Looking at the diagrams in the instructions this is apparently an unvented system and the shower should work ok with this system.Oh, and it's a Hansgrohe. :-?

Title: Re: Shower problem.
Post by TIMBA-WOLF on Sep 14^th, 2011, 5:02pm

Out of curiosity, what sort of hand set (shower head) is on the hose, as some like the one we have is a multi head, and has a PULSE setting..... as well as many spray patterns...

Title: Re: Shower problem.
Post by Lectrician on Sep 14^th, 2011, 5:11pm

Are you saying it is mains pressure cold water and cylinder fed hot water - the cylinder fed from a header tank in the loft?

Title: Re: Shower problem.
Post by m on Sep 14^th, 2011, 5:40pm

TIMBA-WOLF wrote on Sep 14^th, 2011, 5:02pm:

Out of curiosity, what sort of hand set (shower head) is on the hose, as some like the one we have is a multi head, and has a PULSE setting..... as well as many spray patterns...

Timba wolf; There's no mention of a pulse setting and it seems to do it on all settings.

Title: Re: Shower problem.
Post by m on Sep 14^th, 2011, 5:45pm

Lectrician wrote on Sep 14^th, 2011, 5:11pm:

Are you saying it is mains pressure cold water and cylinder fed hot water - the cylinder fed from a header tank in the loft?

Lectrician; That's the one, except the header tank is about a foot above the hot tank in the same cupboard in the back bedroom and not in the loft.

Title: Re: Shower problem.
Post by Lectrician on Sep 14^th, 2011, 5:48pm

I am not a plumber, but I believe that the hot and cold feed to the mixer needs to be balanced, meaning either both tank fed, or both mains fed.

I would assume the cold tap to the bath would be better fed from the header tank, or a pressure reducing valve used.

The hot water may not have sufficient pressure for the mixer with only a foot of height - do you know the minimum operating pressure of the mixer?

Scruff will be likely on later and be able to advise exactly.

Title: Re: Shower problem.
Post by Lectrician on Sep 14^th, 2011, 5:51pm

Can you give us a link to the one you have bought, a link to the manual, or a scan/photo of it?

Title: Re: Shower problem.
Post by m on Sep 14^th, 2011, 6:00pm

Lectrician wrote on Sep 14^th, 2011, 5:48pm:

Thanks for that Lectrician, the recommended operating pressure is 0.2-5 bar.

Title: Re: Shower problem.
Post by m on Sep 14^th, 2011, 6:06pm

Lectrician wrote on Sep 14^th, 2011, 5:51pm:

Can you give us a link to the one you have bought, a link to the manual, or a scan/photo of it?

http://www.plumbworld.co.uk/link/1/pwhg0015installation.pdf

Title: Re: Shower problem.
Post by CWatters on Sep 14^th, 2011, 6:47pm

I'm not a plumber either but... does it do it with the shower hose or head disconnected?

Perhaps the high cold pressure is causing the pressure in the mixer assembly to exceed that in the hot pipe. eg preventing or reducing the hot flow. The mixer would react to that by turning down the cold flow. That might cause the pressure to drop allowing the hot to flow again and triggering the mixer to open the cold again. eg oscillation and pulsing flow.

If removing the head/hose stops it pulsing then perhaps look at putting a pressure reducer in the cold flow.

Title: Re: Shower problem.
Post by m on Sep 14^th, 2011, 8:54pm

CWatters wrote on Sep 14^th, 2011, 6:47pm:

Thanks CWatters, but it still does it without the shower head on

Title: Re: Shower problem.
Post by Lectrician on Sep 14^th, 2011, 9:04pm

Does it do it with just the hot open, or just the cold open, or only when both are open?

Title: Re: Shower problem.
Post by Lectrician on Sep 14^th, 2011, 9:11pm

A quick glance at the manual throws up two lines that concern me:

"Hot and cold supply pressure should be balanced"

"If a water supply is fed by gravity then the
supply pressure should be verified to ensure the
conditions of use are appropriate for the valve."

The diagram shows a minimum head from the bottom of the cold water tank feeding the hot water cylinder to the top of the shower head to be 1m - I doubt you can achieve this if the shower head is on a wall, and water tank is sat above the cylinder in a cupboard?

Going by the diagram for a gravity fed system, your cold feed to the mixer must be from the same cold tank the feeds the cylinder. This is what will then provide equal pressure (although still a minimium of 1m head required for both to provide adequate pressure).

[gallery fullsize]Lectrician/1316031295.png[/gallery]

Title: Re: Shower problem.
Post by m on Sep 14^th, 2011, 9:21pm

Lectrician wrote on Sep 14^th, 2011, 9:11pm:

I think you have hit the nail on the head Lectrician, a reduction valve looks like the answer. Thanks M.

Title: Re: Shower problem.
Post by greg on Sep 25^th, 2011, 4:44pm

wrote on Sep 14^th, 2011, 5:45pm:

.... except the header tank is about a foot above the hot tank in the same cupboard in the back bedroom and not in the loft.

How high is the header tank in relation to the shower head?