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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> Mixer tap problems https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1520441015 Message started by TrevorP on Mar 7^th, 2018, 4:43pm

Title: Mixer tap problems
Post by TrevorP on Mar 7^th, 2018, 4:43pm

Have just removed old bath, which had separate hot and cold taps. The new bath the missus has pick a mixer tap set with hand held shower attachment.
I have been told that as the cold is mains supply and the hot from gravity feed tank I would need to fit a double NRV and pressure reducer to cold, and a blender to both, is this correct because I have very little room under the bath and this setup would require quite a bit of plumbing. Any thoughts?

Title: Re: Mixer tap problems
Post by londonman on Mar 7^th, 2018, 5:11pm

Personally I wouldn't bother faffing about with NRVs on the cold mains feed.

Yes to a pressure reducer on the cold feed to balance the pressure to that dribbling out of the hot tap.

I have no idea what a 'blender' is but gut feel says you don't need them...your mixer tap does any blending.

But Scruff is your man.

Now I am possibly going to rain on your parade. Are you sure that your mixer tap is suitable for low pressure ? A lot of them need more pressure than you will get from your tank and so filling up the bath can take a long time and your missus might get right fed up trying to wash her hair with the water dribbling out of the spray.

I've been there and go the T-shirt and which is why I've fitted a 3 Bar whole house pump to our hot tank supply.

Title: Re: Mixer tap problems
Post by TrevorP on Mar 7^th, 2018, 10:13pm

Well she picked the taps from the ones I picked that stated "low pressure" so was hoping for a descent flow?

Title: Re: Mixer tap problems
Post by thescruff on Mar 8^th, 2018, 12:17am

Easy bit first, good quality taps should have the check valves built in so look at the paperwork.

To balance the pressure you'll need something like this.
https://www.bes.co.uk/water-pressure-equalising-valve-16711

You need to alter the tails to fit the new taps so bring the pipe to the front of the bath and make life easy.

Before you start, check the tap are low pressure, I would also check the cold is mains fed and not from the tank

Title: Re: Mixer tap problems
Post by TrevorP on Mar 8^th, 2018, 7:36am

Checked paperwork, nothing there so will check with supplier about inbuilt check valves. I had already thought about re-routing pipes, you have just confirmed its the best way to go. Only thing about the equaliser is its feed and returns are in 1/2" bsp so pipes in 15mm, was trying to keep hot side in 22mm to keep flow to max?
Or am I looking at it wrong?

Title: Re: Mixer tap problems
Post by thescruff on Mar 8^th, 2018, 11:14am

If the cold is currently 22mm then it's almost certainly tank fed. Hold a thumb or something over the spout can you stop the flow?

This will take the mains pressure down to around 1 bar which would certainly help but still be at least double the hot pressure

https://www.bes.co.uk/adjustable-pressure-reducing-valve-15-22mm-22301

Title: Re: Mixer tap problems
Post by TrevorP on Mar 8^th, 2018, 2:28pm

The mains is in 15mm, and hot in 22mm, at the moment, as said reducing hot down to 15mm and putting NRV inline could drastically reduce flow. The supplier has said no check valves are fitted in taps.
Would the equaliser reduce cold supply, as I see it might?
Thanks for coming back with your advice.

Title: Re: Mixer tap problems
Post by thescruff on Mar 8^th, 2018, 11:50pm

The equalizer will balance the two pressure near as.

With the hot limit, the 15mm as short as possible

https://www.bes.co.uk/pipes-tubes-fittings/pipe-fittings/compression/uk?page=2

Hot side get part No 7369 22mm x 1/2".
The cold side you just need 15mm nuts and olives.

Read the instruction as the flow through the valve crosses over, eg goes in the left port and comes out the right hand port. There is also a flow direction through the valve.

You shouldn't need addition check valves

Title: Re: Mixer tap problems
Post by TrevorP on Mar 9^th, 2018, 8:37am

Ok thanks for that, that's my plan now, much better than I thought. Will let you know final result, cheers.