New tap purchase.......

[JDLDIY]

Just choosing new taps for my bathroom. The taps we like are suitable for low pressure systems, but the bath tap has a requirement to have 0.5 bar pressure.

Our system consists of a direct feed from from the rising main for the cold taps, whilst the hot water comes from the cylinder in the cupboard next door to the bathroom.

Is it worth me being concerned about this and if so how do I go about testing? I have a water pressure meter, not sure how to use it in anger though.

Many thanks.

JD

 

[Silvermoonplumber]

0.5 bar is the minimum pressure that water companies are allowed to push out anyway so i wouldn't worry about it.

 

[JDLDIY]

I thought that was 1 bar? This is the hot tap pressure requirement, so perhaps I'd better check?

JD

 

[JDLDIY]

The update is that I spoke to the people who made my pressure gauge - Monument tools, they did some research and said that to test the pressure with their gauge, it was acceptable to connect it up, turn supply on gently, turn off and then turn on to fully open.

I can't attach it to anything in the bathroom with much success, so I've been using the kitchen washing machine outlet. I get a reading of 0.5 bar exactly. Question is, gravity is helping the water on it's way down a storey, does that actually have an affect on the water pressure though? Is the pressure in my upstairs bathroom likely to be lower? In which case I'd better not go for these particular taps I supose.

Just for my own understanding, what is different about some taps so that they need more pressure to operate adequately? Just wondered what was different about the inner workings.

Am I right in saying that as my cold water is of the direct feed variety (directly from the rising main to the bathroom basin and bath) that I need to fit single check valves? What exactly do they do?

Final question for now - is there a direct relationship between flow in litres per minute and pressure? I could then fill a bucket of water, time it and do the maths.

Thanks again!!

JD

 

[gsportgeorge]

Yes the pressure in the bathroom will be lower than in the kitchen a floor below... by about a tenth of a bar per meter lower it is... if I have got my sums right...

 

[Bahco]

JD

Fit your taps and have done with it.
You seem to be making a meal of it.

Low pressure taps have larger bores to let more water out
.
Do not bother with check valves to your bath as there is no chance that the bath water could back siphon into the mains due to the air gap between your taps and water level.

 

[kevplumb]

wish somebody would tell my daughter there should be an air gap

 

[JDLDIY]

Fit your taps and have done with it.
You seem to be making a meal of it.

Yeah, you are probably right. It's just that the manufacturers of the taps made a special effort to specify 0.5 bar minimum as opposed to all their other low pressure taps operating with a minimum of 0.1 bar (evidently). I can't return them without a large charge and the missus only likes these taps!!!!

 

[Silvermoonplumber]

The only thing you would find useful to fit on the taps is an isolating valve (service valve) on each pipe which means you could then isolate each of them if you ever needed to work on the taps in the future. Pressure and flow rate have nothing in commmon.

Pressure is the volume/area. For every 10 metres of height you will get 1 bar of pressure. Lower pressure would normally be balanced out by a larger diameter pipe.

Just fit the taps and enjoy them.

 

[croydoncorgi]

0.5 bar is the minimum pressure that water companies are allowed to push out anyway so i wouldn't worry about it.

Yes, maybe. But that's not the issue! He has mains-driven Cold taps and (apparently) Hot taps off a tank. If the pressures are wildly different on a bath mixer, the cold will push the hot back into the tank except at low flow! If it's a shower mixer, adjusting the temperature with lopsided pressure will be 'difficult' (read: impossible!).

Pressure is the volume/area.

Rubbish! Static head depends on only HEIGHT.

For every 10 metres of height you will get 1 bar of pressure.

Correct

Lower pressure would normally be balanced out by a larger diameter pipe.

Not correct! Whatever do you mean???

OK - if FLOW is the problem, for a GIVEN pressure you'll get more out of a bigger pipe. But the problems here are (presumably) unbalanced pressures in hot and cold and possibly also too little pressure from the hot to hold the hand shower control in the ON position.

If the makers say 'minimum 0.5 Bar' , you've got 0.4 AND the thing works poorly after you fit it, you've wasted the cost of the tap AND the cost of your time to prove something you already knew!

 

[Bahco]

Your taps need .5 bar to operate and you have already stated that this is what you have so fit the bloody things.

You have not said they are mixer taps so go ahead.

 

[JDLDIY]

Sorry if I didn't make it clear BAHCO - it is a single lever mixer tap. I'm now leaning towards choosing a different one, looks like it's back to the bl***y shops for me today!

JD

 

[Bahco]

OK

If you wish to keep this tap you will need to change your cold supply (to it) from mains to tank fed.

This will involve taking pipework from your cold water tank to supply it.

Not recommended as you will be drinking stored water and all kitchen
water should come from the main.

Change your tap for 2 single ones, it will be less hassle

 

[Silvermoonplumber]

Woh, calm down. The guy did not say that it was a mixer. he stated they were TAPS plural, so what I said made sense. Pressure is not the same as static head. I know static head is affected by height (like I said 10m = 1bar pressure)

A larger diameter pipe to his HOT tap (like he started off saying) would give the same pressure but a greater volume of water would come through.

Of course you can't have a mixer with different pressures from hot and cold, but he didn't clarify that to begin with!!!

0.5 bar is the minimum pressure that water companies are allowed to push out anyway so i wouldn't worry about it.

Yes, maybe. But that's not the issue! He has mains-driven Cold taps and (apparently) Hot taps off a tank. If the pressures are wildly different on a bath mixer, the cold will push the hot back into the tank except at low flow! If it's a shower mixer, adjusting the temperature with lopsided pressure will be 'difficult' (read: impossible!).

Pressure is the volume/area.

Rubbish! Static head depends on only HEIGHT.

For every 10 metres of height you will get 1 bar of pressure.

Correct

Lower pressure would normally be balanced out by a larger diameter pipe.

Not correct! Whatever do you mean???

OK - if FLOW is the problem, for a GIVEN pressure you'll get more out of a bigger pipe. But the problems here are (presumably) unbalanced pressures in hot and cold and possibly also too little pressure from the hot to hold the hand shower control in the ON position.

If the makers say 'minimum 0.5 Bar' , you've got 0.4 AND the thing works poorly after you fit it, you've wasted the cost of the tap AND the cost of your time to prove something you already knew!

 

[Silvermoonplumber]

BAHCO,
best advice for this guy definitely.
He could run pipes from Cold Water Cistern to cold bath taps, nothing wrong with that just a damn sight easier to but seperate taps.....

OK

If you wish to keep this tap you will need to change your cold supply (to it) from mains to tank fed.

This will involve taking pipework from your cold water tank to supply it.

Not recommended as you will be drinking stored water and all kitchen
water should come from the main.

Change your tap for 2 single ones, it will be less hassle