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Discuss Mixer tap pressure low in the DIY Plumbing Forum area at PlumbersForums.net

Bogart

Messages
513
Never gave it a thought, regarding pressure suitability, when the boss said " Oh I like that tap".
Hence stuck with a tap specified as minimum pressure 0.75bar and me with a gravity system at max height 5m, ie 0.5 bar at best.
So as I see it I have 2 options. Fit some sort of pump, only needs to feed this one tap or replace the tap. On the second option a lot
of taps quote suitable pressure 0.2bar to 5 bar. That seems a hell of a range and puts me definitely at the bottom end.
I do not want to buy another tap and find is not much better. Any suggestions?
 

Timmy D

Esteemed
Gas Engineer
Subscriber
Messages
528
The 0.2 is to cover vented domestic water systems like yours.

The 5 bar will cover unvented (mains pressure).

I’d just get a new tap.

Where is the tap? Bathroom/kitchen? Are both supplies the same pressure?
Kitchen, mains cold would be high and vented hot would be low. Just something to bear in mind as if you install a thermostatic tap here, the cold will force up the hot pipe.

There are a few thermostatic taps suitable for the above situation.
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Messages
30,341
Solutions
1
Two options upgrade your system to mains pressure and keep the new tap or change for a low pressure tape eg with the good old 1/2 washer style
 

Bogart

Messages
513
The 0.2 is to cover vented domestic water systems like yours.

The 5 bar will cover unvented (mains pressure).

I’d just get a new tap.

Where is the tap? Bathroom/kitchen? Are both supplies the same pressure?
Kitchen, mains cold would be high and vented hot would be low. Just something to bear in mind as if you install a thermostatic tap here, the cold will force up the hot pipe.

There are a few thermostatic taps suitable for the above situation.
Is a kitchen mixer. I spoke to a guy at Stuart Turner yesterday discussing this. It was decided what was needed was a negative head pump due to uneven pressures available. Was all good until I was told the pump must be no further than 4m away from the HW cylinder , so that knocked that on the head. So am now looking for a new tap. And as you rightly state needs to be the correct
tap so if mixing the cold does not push the hot water backwards.
 

Timmy D

Esteemed
Gas Engineer
Subscriber
Messages
528
Is a kitchen mixer. I spoke to a guy at Stuart Turner yesterday discussing this. It was decided what was needed was a negative head pump due to uneven pressures available. Was all good until I was told the pump must be no further than 4m away from the HW cylinder , so that knocked that on the head. So am now looking for a new tap. And as you rightly state needs to be the correct
tap so if mixing the cold does not push the hot water backwards.

This is really a FYI and to clear up any potential misunderstanding.

You said a negative head pump was recommended due to uneven pressures...

The options are either a positive or negative head pump.

The “default” as such is a positive head pump.

A negative is used when the highest outlet (typically a shower head) is 600mm or less below the bottom of the cold water tank.

A positive head pump relies on the tank water pressure to start the pump. When it’s close to the tank, there’s insufficient pressure to start it. So we use a negative pump.

You can’t put the pump next to the cylinder?

Or depending on age of current cylinder, upgrade to an unvented (mains pressure/flow permitting).
 

Bogart

Messages
513
This is really a FYI and to clear up any potential misunderstanding.

You said a negative head pump was recommended due to uneven pressures...

The options are either a positive or negative head pump.

The “default” as such is a positive head pump.

A negative is used when the highest outlet (typically a shower head) is 600mm or less below the bottom of the cold water tank.

A positive head pump relies on the tank water pressure to start the pump. When it’s close to the tank, there’s insufficient pressure to start it. So we use a negative pump.

You can’t put the pump next to the cylinder?

Or depending on age of current cylinder, upgrade to an unvented (mains pressure/flow permitting).
Stuart turner said a positive pressure pump would not work in my situation. Pump next to the cylinder would be possible but not without a lot of additional pipework involved. The hot water exits the cylinder going right. There is about
 

Bogart

Messages
513
As they say a picture paints a thousand words. Attached are 2 photos.
Second shows arrangement at top of HW cylinder. The 28mm pipe exiting right is the hot feed to all baths and basins. It is approx 300mm in length with a gate valve in the middle before it disappears behind the plasterboard. The 22mm pipe exiting directly above the HW cylinder is the pipe feeding a shower via a Stuart Turner twin monsoon seen in first pic the copper pipe coming in from top right. Now my dilemma is/was how to fit a pump. The only real tap with a problem is the monobloc in the kitchen, with as mentioned before a pathetic flow rate, caused by it being a high pressure tap on a low pressure setup. All other hot outlets are fine.
The ST pump in first pic is a 2 bar twin Monsoon, feeding just the one shower. I did think of a few options. One was to put a pump
on the shelf above directly over where the 28mm gate valve is. Dump the gate valve and insert a pump into the pipework there. Not sure how it would like bouncing around on a slatted shelf though I could beef that up. To put a second pump on the floor like the current pump would involve a lot more pipework. One other option I thought of was make the ST pump do the whole house hot.
Or just buy a low pressure tap.
 

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