Mains pipe size

[Russell griffiths]

Evening, could be a couple of questions here mixed together, 

if we get planning I’m going to have to put in a new main as the one we have is leaking, so what would be your preferred size for a main pipe that has to run a distance of aprox 110m 

the house will have 3 beds all with en-suite all with showers, also a cloakroom with toilet and kitchen and laundry. 

Cheers for your input. 

[Jeremy Harris]

Depends.

 

32mm MDPE will drop 1 bar over 110m at a flow rate of 40 l/m (approximately 4 normal showers running at the same time).

 

You need around 1.5 to 2 bar at the house as a rule of thumb.

 

So, if you have around 3 bar at the water main end of the pipe, 32mm should be fine. 

 

If it were me, I'd get a pressure gauge and have a look at what you've got at the moment.  You don't need to measure at the main, if you close all the outlets at the house end and put a pressure gauge on that end it will give you the static pressure.  If that's high, say 4 to 5 bar, then you can be confident that 32mm will be fine, if it's a fair bit lower, you may need to rethink.

Edited December 8, 2017 by JSHarris

[Russell griffiths]

Any links to a reasonable pressure gauge?

will I need one for testing ufh and other services in the new place? 

If this is the case should I get a better quality one?

 

my incoming main is 50mm that reduces to 32mm which then has 20mm tees of it to feed various standpipes and our old cabin, will taking a reading at one of these 20mm pipes give a false reading should I go back to the 32mm to do the pressure test?  

Cheers. 

[Onoff]

I just bought the Monument one from Screwfix. Been fine. They do a Rothenberger for another fiver.

[Jeremy Harris]

15 minutes ago, Russell griffiths said:

Any links to a reasonable pressure gauge?

will I need one for testing ufh and other services in the new place? 

If this is the case should I get a better quality one?

 

my incoming main is 50mm that reduces to 32mm which then has 20mm tees of it to feed various standpipes and our old cabin, will taking a reading at one of these 20mm pipes give a false reading should I go back to the 32mm to do the pressure test?  

Cheers. 

 

You can take a static reading anywhere, just make sure no one has an outlet open when you do.  The static pressure will be more or less equal everywhere if the pipe run from the main is fairly level, as I suspect it is knowing your location.

[IanR]

We went 32mm for 130m run. Any bigger and you have to chlorine rinse before commissioning. 

 

I was surprised that the meter,  restricts to 15mm, but was told there's not another option. 

 

Still get 6 bar at the house though. 

[Russell griffiths]

We have a 50mm main that is fed from a metre via a 25mm pipe. 

Unsure how this all works, but it’s been like it 20 years with no problems. 

[Nickfromwales]

Can't you excavate to find the start of the 32mm section and then camera survey to get the location of the joists & the 50x32mm reducer? I'd be doing my damnest to find the leak, and if it could be fixed in a day then bingo. Camera survey should be able to give you the distance from entry to the junctions / joints so you could try and work with what you've got. 

Do you intend to dig / follow the existing trench pipe run and lay alongside the leaking main anyhoo? 

I wouldn't give up so easy TBH, how much is the new main estimated at ?

[Russell griffiths]

ive Been doing a bit of internet browsing and started to find 50mm pipe at better prices so will do a bit more leak hunting, tbh I didn’t know you could put a camera down a water main I thought it was only for drain surveys so I might be able to find one of the joints. 

These must be the first point to look for a leak or at least an ideal place to run a new section from. 

Thanks all. 

[Onoff]

Anyone got one of these?

 

https://www.ebay.co.uk/itm/Water-Pipe-Leak-Detector-Electronic-Stethoscope-Earphone-Detection-Equipment-Kit/322555337835?hash=item4b19cbdc6b:g:aq4AAOSwjvJZQkPG

[Russell griffiths]

I watched a you tube vid and since brought a doctors stethoscope, I now need to work out a way to connect the stethoscope to a long metal spike to stab in the ground. 

Always seems to be a project to do in the garage. 

 

 

[Onoff]

16 minutes ago, Russell griffiths said:

I watched a you tube vid and since brought a doctors stethoscope, I now need to work out a way to connect the stethoscope to a long metal spike to stab in the ground. 

Always seems to be a project to do in the garage. 

 

 

 

I tried that. Think it might have worked but my leak was under a concrete path rather than under "dirt" along the run. Stick it in a hollow tube concentrates the sound. I used a scaffold type metal tube the same dia as the stethoscope. Make a good directional mike if nothing else!