water pressure testing

[therebel]

what is the recognised way of testing mains water pressure. I am looking at having an electric shower fitted and the pressure is affecting my choice.

[BigWallop]

A web search for the word "Manometer" will show you what's needed. But an easy test is placing your thumb over the kitchen sink cold tap, and then slowly turn it on. At a certain point you won't be able to hold the pressure back, and this shows a good mains water supply pressure. A good mains water supply pressure is what's needed for a good electric instant shower.

The next thing you need to find out for an electric instant shower is the electrical supply routing. A good shower is anything above 8.5kW and mat need to be supplied with large cables if the routing demands it.

Hope this helps a little.

[Set Square]

To measure static pressure, you need a pressure gauge. Screwfix do one for a tenner or so which will attach to any outside tap which has a threaded spout to take a hose attachment.

However, static pressure (at zero flow) doesn't tell you very much because if there are restrictions in your supply pipe (long thin pipe, etc.) the pressure may drop dramatically when you turn a tap on. So you also need to measure *flow* - which you can do with a bucket and stopwatch. Weigh the bucket empty and then direct the full flow of the kitchen tap into it for a timed period and then weigh it again. If the timed period is one minute, the weight difference in Kg gives the flow in litres/min.

[Jim]

Which will be absolutely useless unless:

a) you use a super dense fluid

or b) possess a huge manometer (ooh err)

Can I suggest the use of a pressure gauge that reads 0-5 bar or if this is not available then build a manometer around 200 ft high

[Fred]

You may also find a rather large difference in pressure between 8.00am in the morning and 3.00pm in the afternoon!

[John Stumbles]

You can make your own with some clear plastic tubing filled with water. It'll need to be 30 metres or so high, though.

[John]

Unless you have access to a Mercury Manometer at around thirty feet tall or a water manometer at around 300 feet I would suggest you use a bourdon gauge (Dial type) which is fairly easily obtained from a decent plumbers merchant for around a tenner. However standing pressure is one thing, dynamic pressure under flow conditions is entirely different as it may be that the pipework restricts the flow at the outlet point.

[Tony Williams]

In article , John wrote: [snip]

Below are the quoted requirements from our electric shower booklet.

" ... a mains water supply with a minimum running pressure of 1 bar (14.5psi) at a minimum flow rate of 8 litres per minute and a maximum static pressure of 10 bar (145 psi)."

" ..... can be taken from a cold water storage cistern provided there is a minimum head of 30m above the sprayhead. It must be an independant supply to the shower only."

That second possibility is a little unrealistic for most houses.

[Set Square]

It's cobblers, anyway! 1 bar requires a head of about 30 feet - *not* 30 metres!

[Ian_m]

A water manometer must be taller than a house as:-

1. The water must get into loft storage tanks in many properties.
2. I have hosed down the moss in my last house using house pipe on the roof and had no water pressure problems up there.

[Set Square]

True. For a typical 4 bar pressure, it would need to be at least 120 feet tall.

But that's not the point of this part of the thread. I was commenting on the fact that the shower spec is wrong in implying that you need a 30 metre head to get 1 bar at the shower.

[Tony Williams]

My typo. Try 10m.

[Set Square]

That's better!

[s--p--o--n--i--x]

Contact the water board. Southern water will test your pressure for free.

sponix

[s--p--o--n--i--x]

Correct. 1 bar is 10 metres or 14.2 psi.

sponix

[Dave Plowman (News)]

Crikey - that's an old post you're replying to? ;-)

[News]

14.7 psi