Long communication pipe to main - 32 or 50mm?

[Cauk]

I’m still investigating costs for our build.

 

Nearest water main is 600m down the road, height difference is from one end to the other is about 7.5m.

 

We have an easement to put the communication pipe in the field next to the road and have costs for the trench, all reasonable (sharing with a neighbour who is also going to put a pipe in).

 

Current quote is for a 32mm supply and this is the default for Southern Water.

 

The house will be 4 bed 4 bath and I’d like to look at GSHP for heating ~3000sqft.

 

Some have suggested I need a 50mm supply to account for the length of connection. I don’t have a read on the pressure at the mains. The nearby houses describe it as ‘good’ but that isn’t science.

 

Do I need 50mm? I’ve enquired with Southern Water to find out if 50mm is even possible; their response:

 

1. As southern water cannot advise the customers on the pipe sizes required, please consult your plumber for the required flow rate and confirm the exact required pipe size.
2. Please confirm the flow rate if your requirement is 50mm pipe size. 

 

I’ve spent time on google but it looks like flow rate is hard to calculate? Is there an easy button?

 

I don’t have a plumber involved yet as I’m still investigating everything.

[Cauk]

Typo that I can’t edit for some reason - height change over the run is about 2.5m.

[tonyshouse]

50mm for me, but I would go cisterns in the loft too

[PeterW]

7 hours ago, Cauk said:

sharing with a neighbour who is also going to put a pipe in

Is that sharing the trench or the pipe ..? Are they above or below you on the connection ..?

 

7 hours ago, Cauk said:

Please confirm the flow rate if your requirement is 50mm pipe size. 

 

I’ve spent time on google but it looks like flow rate is hard to calculate? Is there an easy button?

so if it’s one house connected, you want to go for a minimum 2 bar and 25l/min to get decent showers running in parallel. 
 

pressure loss on 50mm would be around 0.18 bar, on 32mm it will be 1.1 bar over 600mm at 25l/min. Ideally you want 3 bar at the house so you need to understand the main pressure and the minimum they will guarantee at the property. 
 

Where are southern suggesting the meter will go as that is always the restriction 

 

 

[Nickfromwales]

If 4 bed / 4 bath, how many occupants? If bathing is sporadic you can get away with a lower flow, but as @PeterW says, we need to know more. I think it would be a good idea for the comms pipe to be 50mm to the point where your neighbour T's off, if that will be where their meter is, and then you pick up from that 'manifold' in 32mm to come to your boundary and your meter.

Much more info needed, please. 

 

[scottishjohn]

different here

-I asked scottish water about a similar situation and they would only run 2 sperate pipes from the mains anything else would be classed as sub main ,as no shared supplies allowed -

 a sub main and any maintenance would be not their responsibility it would be be mine --

I would not accept that --

would be same problem as shred driveway maintenance costs---

[scottishjohn]

2 hours ago, scottishjohn said:

would be same problem as shred driveway maintenance costs--

should have read SHARED driveway 

[Cauk]

Thanks all; apologies for not being clear. Looking at more documentation I may have used the wrong terminology by calling it a communication pipe - maybe it's 'supply pipe'.

 

The water main is 600m down the road. Height change from one end of the proposed pipe to the other is ~2.5-3m.

 

There is our plot, a neighbouring plot and a field.

 

The cost from southern water to bring the main to the site is significant, so the current proposal is for us to run the pipe to them and connect to the main.

 

There would be 3 pipes - ours, the neighbour and one for the field - they would all be laid in the same trench.

 

All 3 pipes would run independently - each would connect to the mains and the meter would i believe be at the mains end of the pipe (i.e. 600m away from the property). Each pipe would serve only one property.

 

SW would only guarantee the pressure at the meter which will be 600m away; I'm having a hard time getting information out of them so I don't know what the pressure available actually is.

 

I've asked SW if i could have a 50mm connection, to answer that question they want to know my required flow rate.

 

4 bed/4bath with 4 adults - so likely we will need to use 2 showers at once, maybe 3.

 

I'm looking at GSHP for heating - I assume the question of vented/unvented for that would depend on water flow and pressure - so it's a bit chicken and egg.

[Cauk]

I’m going to put a 50mm pipe in while we have the trench. If I can only get a 32mm connection my understanding is that the larger pipe on the 600m run won’t cause any issues?

 

One of the laying quotes included sanding, the other said it’s not necessary. Substrate is chalk. Ive read that pipes can oscillate and so sanding or conduit is recommended - for peace of mind and the small additional cost it seems sensible to get it sanded or in conduit too?

 

Final question - the final 100m of the run is also along the path of where we will bury power - can they share a trench or do we need to dig two? (I’ve done no research yet, just asking while I’m here!)

[Temp]

1 hour ago, Cauk said:

I’m going to put a 50mm pipe in while we have the trench. If I can only get a 32mm connection my understanding is that the larger pipe on the 600m run won’t cause any issues?

 

No issues and it will still help maintain pressure.

 

1 hour ago, Cauk said:

One of the laying quotes included sanding, the other said it’s not necessary. Substrate is chalk. Ive read that pipes can oscillate and so sanding or conduit is recommended - for peace of mind and the small additional cost it seems sensible to get it sanded or in conduit too?

 

Yes to sand, no need for conduit. Use narrow bucket on digger to save on sand.

 

1 hour ago, Cauk said:

Final question - the final 100m of the run is also along the path of where we will bury power - can they share a trench or do we need to dig two? (I’ve done no research yet, just asking while I’m here!)

 

Yes. See below. You also need marker tapes.

 

[Temp]

PS: Instead of asking for quotes for the whole job you might also consider hiring a "man and excavator", buy your own pipe and sand.

 

 

[Nickfromwales]

For 3 showers, you’ll still need a sizeable UVC and an accumulator, regardless of the 50mm pipe. At best the 50mm pipe will stave off the resistance of the 32mm pipe vs 600m distance, but will do zero to improve things that significantly because you’ll always be governed by the max potential deliverable by the stopcock and the meter. Pipe size is one discussion but it only conveys what you’re given. 
Set the pipework up to accept an accumulator and see how you go, but 3 showers plus a loo flushing / appliance filling will be a huge ask of any domestic supply, let alone a 600m long one with over a one storey incline. 
FYI, that incline will probably cost about 0.8-1.0 bar of ‘head’. Can you get a reading from someone’s outside tap at / near the boundary, for reference? 

[Mr Punter]

I would want to extend the main if possible.

 

I have a block of 8 converted flats and noticed the other day that they are all served by a single 15mm supply, teed off to 8 meters!

[Cauk]

Thank you all - very helpful.

 

Will design with space for accumulator just in case.