External Taps Supply Routing

[BadgerBadger]

We have a temporary water supply at the moment and about to switch it over to our final connection.  We have a meter on the boundary so it's a straightforward 32mm MDPE run from this, through a duct and into to our plant room.  Can't quite agree with myself on the best way to supply our external taps.  Ideally we'd like 3-4 taps dotted around the building and up at the furthest corner of our plot.

 

I could branch off the 32mm MDPE and run to all tap locations - but how do I handle isolation/freezing/drain-off?  The tap uprights visible on the building are like to be copper to keep them a bit more subtle, so could be prone to splitting. Thought about installing an extra access box to allow for access to an MDPE isolation valve, then just open all taps? Or is a drain-off practical? I guess double-check valve on the branch would then just be buried. 

 

Alternatively, I thought about putting the branch/isolation/drain-off port in the plant room, and then running a second MDPE back out through the duct to all the external taps.  But feels a bit awkward!

[JohnMo]

11 minutes ago, BadgerBadger said:

32mm MDPE run

That's a big pipe, are sure you need that big?

 

Our water comes into the house through a duct under the foundations. Up to the stop cock, prior to any pressure reduction the pipe takes a turn left and down to its own isolation and the down through the same duct and then up to the outside tap.  Stop cock stops all water flow, and outside tap has its own isolation also. 

 

 

[garrymartin]

This is what I have in my notes;

 

32mm external MDPE, into Plasson stop tap, convert to copper, double-check non-return valve, drain valve, (PRV if >5 bar), external taps (with isolating valves and non-return valves), then 28mm copper on to all the internal feeds (UVC, hot manifold, HRC manifold, etc.)

 

EDIT - just found a question I still haven't resolved; should PRV come *after* feed for external taps? Maybe someone else can advise on that one and I can update my notes with the answer! 😉

Edited May 2 by garrymartin

[JohnMo]

20 minutes ago, garrymartin said:

should PRV come *after* feed for external taps

Yes 

[garrymartin]

Thanks @JohnMo - I originally had "32mm external MDPE, into Plasson stop tap, convert to copper, double-check non-return valve, drain valve, (PRV if >5 bar), external taps (with isolating valves and non-return valves), PRV, then 28mm..."

 

So the PRV came after the external taps. I removed it because I'd at some point I added the (PRV if >5 bar) and assumed it was a duplicate, but perhaps it's both?

 

Is there a reason to keep the external taps under 5 bar pressure?

[JohnMo]

1 hour ago, garrymartin said:

Is there a reason to keep the external taps under 5 bar pressure?

Not really, we use huge long hose pipes (200m) so happy with every drop of pressure.

[Susie]

A separate thought for you is that if you need a lot of outside taps is that because you will need a lot of water e.g. gardening and hot tubs. If you tee of after the meter before you enter the house you could have a separate meter for water used and not disposed down the drain. My water board gave me the meter free if I dug the hole. I think despite all my water saving the outdoor taps still save me money. 
 

[Mike]

2 hours ago, garrymartin said:

32mm external MDPE

Worth knowing that, at least in some regions, the water standing charge is based on the size of the meter, so not necessarily good to go with a fat pipe unless you need it / don't mind.

[garrymartin]

46 minutes ago, Mike said:

Worth knowing that, at least in some regions, the water standing charge is based on the size of the meter, so not necessarily good to go with a fat pipe unless you need it / don't mind.

From what I've read, I see little to no disadvantage (aside from the small extra cost for 32mm pipe and fittings over 25mm) to installing 32mm MDPE from the meter to the dwelling even if the meter connection needs to drop down to 25mm. Indeed, there are several advantages including reducing pressure loss over longer distances. At least in my area, the standing charge appears to be the same, and even in areas where it isn't, we're talking £2-3 per year difference from what I can see.

[garrymartin]

Found the reference for the second PRV I think - it came from some guidance from @Nickfromwales on G3 certifiable UVC installs in new builds.

 

 

[garrymartin]

Also, if you're doing irrigation in the garden and the supply pressure is high, you may need another PRV on the outside connection for that dedicated purpose...

 

"Water from the mains supply will typically sit between 3-4 bars of pressure which is too high for most irrigation systems, usually only needing around 1.5 bar. If used with mains pressure, irrigation systems can be much more costly to run, resulting in less efficiency in water distribution and even cause a burst in the system. To get around this, installers should ensure PRVs are installed alongside isolation valves to better regulate the pressure released from the tap."