Water mains pipe size?

Question

In the process of getting my water mains renewed into the property. Going from lead to plastic & my plumber has suggested using 25mm (18mm Internal bore) from the external stopcock to inside the property. Some people have suggested that i use a 32mm (25mm internal bore) pipe as we wan to get a megaflow in the future.

It will service two bathrooms & maybe a downstairs shower room. My plumber has told me that 32mm is over kill while other people are saying that thew 32mm is the one to go for as the costs difference is minimal & i should look to get maximum flow rate.

Believe that the current pressure is under 2 bar & current flow rate is around 9ltr per minute.

Please help as the work starts next week

thanks for your help so far - should have added that the water company are going to renew from the main to my boundary with 35mm or 32mm.

Think I will tell my plumber to put the 32mm in as one of you said there is no harm in having too much?

20mm is being renewed internally to the tank with 15mm to the kitchen sink

boundary stop **** to internal stopcok is just under 12 metres

Answer 1

i work in the water industry, and help people with these problems frequently. for a single property, a 25mm pipe will be more than adequate. Plus, your local water company will probably only renew like for like, so to get a 32mm connection will cost more than renewing to the existing stop tap at the boundary. If you do put in a 32mm pipe, but keep the exisiting stop tap, it defies the point, as you will only ever get the maximum flow that the part of the pipe before the stop tap will allow... 25mm should be more than enough as long as the pressure and flow at your boundary are good. i would ask your local water company for a test at the boundary to ensure that replacing the pipe would improve the supply. sometimes there can be blockages on the ferrule connection off the main, or a leak on the pipe between the main and the stop tap. Phone up for an appointment with an engineer. listen to them, they should confirm that your plumber is indeed correct, and the other people don't really know what they are talking about.

Answer 2

Mains Water Pipe Size

Answer 3

You're getting lots of Engineers opinions today! :) Why not mine, too.

2 bar huh? Lessee... that's 29psi. Pressure seems kinda low to me. I would expect something more like 4 or 5 bar at the meter stopcock. But that's a different problem and not what you asked.

The one thing you didn't tell us is how far it is from the service stopcock to the house.
If it's not far then the 25mm pipe should be fine however I'd go with the bigger pipe. If it runs any distance then the pressure drop in the pipe itself starts to become an issue even though the stopcock may only be 25mm. Within the limits of sanity, bigger is better where water pipe is concerned.

Have your plumber do a pressure drop calculation based on pressure at the meter, free flow volume at the meter, and distance to the house. You should lose less than a couple psi; about 1/8bar. You can't get pressure loss to zero, but see how low you can reasonably get.

Answer 4

This Site Might Help You.

RE:
Water mains pipe size?
In the process of getting my water mains renewed into the property. Going from lead to plastic & my plumber has suggested using 25mm (18mm Internal bore) from the external stopcock to inside the property. Some people have suggested that i use a 32mm (25mm internal bore) pipe as we wan to get a...

Answer 5

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Answer 6

maybe now having a 32mm pipe will make very little difference, but who knows what will happen to the house in the future, what new water devices there will be.

sounds to me like you need the 32mm, imagine both bathrooms working and the shower room, the dishwasher, the washing machine, the toilet filling and your son pressure washing the car all at the same time.....

also at peak usage times the pressure may well fall below 2bar and it will be better to have a high flow at low pressure, at least that way there will be something to come out of the taps.

Answer 7

defiantly go for 32mm. to much is better than not enough. the price difference in nothing. you are going to need a good supply to feed 2 bathrooms. 9 litres/min is terrible. most new boilers need at least 12-16 litres /min. go for over-kill. i am also an engeneer for british gas & deal with low water pressure problems all the time. water volume is more important

Answer 8

it depends on how high you are up the block if you are on the ground floor i would run a new main as it should not be as dear as if you are on the top floor .and it all depends on if the tanks are still in the loft in which case you should have your own supply from the tank and you could fit a pump as it is not coming from the mains call a good plumber and get his advice it could save you money in the long run hope this helps as far has the combis are concerned it is like a motorway full of cars coming to a single carriageway you stop

Answer 9

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Answer 10

Considering the few quid a larger bore pipe and fittings cost go for the larger bore.