what should the water pressure and flow rate be

bernlyn · 3 February 2006 at 12:43AM

i am going to put a bathroom upstairs but the boiler is downstairs and the water storage tank is in the way of the new bathroom. the system is very old and britsh gas recomends that i look into getting an complete new system.

so knowing how expensive they are i called in another company and explained about the upstairs b/room. they recommended a condense combi boiler BUT on turning the tap on he said that the water pressure was not good.

i then contacted my water suppier and they sent some one out to test it. he said that my water flow was not good but the pressure was ok at 4 bar. i then pointed out to him that the gauge is actually reading 3.5 and not 4 bar as he said. he said it was still good. but i need to replace the pipes leading to the house.they have to bring a seperate feed from the mains to the pavement outside my house and i then have to pay someone else to connect it to the house. i was quoted +- £1600 for this. but i got the impression the he wasnt being totally honest.

1] how pressure is needed and how much water flow is needed for an upstairs bathroom
2] what should the water flow be for the house as it is now
3] is they anyway that i can redo these tests

pixie1 · 9 February 2006 at 8:56AM

Water companies give you a min of 10mh (1bar) at the main stop to of your property as long as that is in the pavement.

If you think that the pavement level = 0mh the height diff between that and your bathroom is approx ?? 7m (im guessing) so if you have 10mh (1bar) at the stop tap you then get 3mh (0.3 bar) upstairs. As you have 3.5bar = 35 mh you have plenty of pressure. Flow is different because it depends on the size of pipes etc.

Something I would be wary of is fitting a power shower or something simular that requires a constant pressure of over 10mh (1bar) because if your water company desides to reduce the pressure in your area which they all do as it saves so much money, you could be left having to replace your equiptment as they only promise 10mh.

Your local water company should have a water regulations department, they may be able to help you more as they are normally ex-plumbers.

Hope this helps and that I have confused you even more.

PM me if you need any more help. Im an ex-water company employee so I may be able to find some more things out for you.

pixie1 · 9 February 2006 at 8:58AM

I forgot to add, it sounds as though you may either be on a shared supply or have an old lead service pipe. Some water companies offer free lead replacements where they do a lot for the work for you and then you just connect to it, i wouldnt of thought it would be the same cost as you were quoted, but every water company is different, it just depends where they are focusing their money on at the time.

bestyman · 9 February 2006 at 11:07AM

Hi,
This link may help.http://www.thameswateruk.co.uk/en_gb/Downloads/PDFs/PBS_Water_Pressure_and_Flow_Rate_in_your_Home_955kb.pdf

But some combi boiler aim to have a hot water flow rate of 14 lites a minute so the 9 litres a minute that they suggest as ok isnt IMO. Also bear in mind that as well as the 14L from a hot tap you may also wish to have a cold water tap running too ( running a bath ) .

Regarding the info on a power shower. A combi boiler ( in 99% of cases) would not have a power shower as a power shower pumps tank fed water and a combi has no tanks. But an option ( a bit unusual but it would solve the problem) would be to have a large tank and cylinder installed that would provide tank fed cold water to the bath and shower and hot water to all the taps/shower. A power shower could be fitted to this.

Hope tha above makes sense. In effect you would have your own little resovoir( the tank) in the loft that could be emptied quickly when required( power shower or bath time) and fill up slowly from the limited flow you have. The disadvantage is the extra cost of cylinder and tank installed.

Or, you could arrange for a plumber ( probably much cheaper)to put a new main in and just get the water board to connect it to the outside supply. The trenche needs to be 2foot 6 deep and the major cost is the digging so if you are handy with a shovel no reason why you cannot dig it yourself.

Another point is this. Suppose the supply up your street is an old lead 1/2 pipe that say runs for 50 metres then to your pavement stoptap then 20 metres to your home. If you just replace the 20metre section in your garden the improvements will be little. For this reason check with the water board that the supply at the other side of the stoptap is adequate size.

what should the water pressure and flow rate be

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