£2k for water main upgrade, other options?

Iknowcraig · 30 Oct 2018

Hi all, I have ben quoted £2k by southern water to upgrade my water main from 20mm MDPE to 32mm. This is due to them needing 4-way lights in the road while excavating.

The house currently has 1 bathroom but I will be adding two ensuites and wanted to use an unvented system. I also wanted to avoid noisy pumps needed on a gravity system. Would people recommend I go for the water main upgrade, or are accumulators worth looking into, static pressure is 4 bar so I could use a passive accumulator I believe?

Many thanks!

Ian H · 30 Oct 2018

Have you dug at your bondary to see if it’s 20mm there?

Iknowcraig · 30 Oct 2018

Ian H said:
Have you dug at your bondary to see if it’s 20mm there?

yes, definitely 20mm blue mdpe incoming

John D v2.0 · 30 Oct 2018

Do you really need to upgrade the whole lot? What percentage of the 20mm is under the road and what inside your property boundary?
It doesn't matter which part you increase its the percentage that matters.

Iknowcraig · 30 Oct 2018

John D v2.0 said:
Do you really need to upgrade the whole lot? What percentage of the 20mm is under the road and what inside your property boundary?
It doesn't matter which part you increase its the percentage that matters.

I have no way of knowing what percentage of 20mm is under the road surely? I have already trenched and run a 32mm pipe to the edge of the road ready to be connected before I knew how much it would cost. Surely the percentage isn’t important, if at any stage the run is in 20mm mdpe, the flow rate will be reduced to whatever the flow at 4 bar through 20mm is?

John D v2.0 · 30 Oct 2018

Iknowcraig said:
if at any stage the run is in 20mm mdpe, the flow rate will be reduced to whatever the flow at 4 bar through 20mm is?

No that's not how resistance works, it's per metre. So just upsize any part of the run.
But we are assuming under the road really is 20mm, perhaps there's a joint just out of sight down to some lead pipe that's half squashed.
Regarding the percentages you know how much is your side, the water co should have worked out how much run of pipe needs digging so ask them.
Or since you've already put the bigger pipe in just connect your new pipe to the old and see what the result is.

OvertonPlumber · 31 Oct 2018

2k is quite reasonable for a 32mm tapping. Normally its a 5-6 bedroom detached house on a 32mm with a 28mm stopcock.

Iknowcraig · 31 Oct 2018

MrBenchmark said:
2k is quite reasonable for a 32mm tapping. Normally its a 5-6 bedroom detached house on a 32mm with a 28mm stopcock.

Thanks, I am in a 4-bed detached and we are adding a bedroom, so sounds like the right size!

fezster · 31 Oct 2018

Iknowcraig said:
Surely the percentage isn’t important, if at any stage the run is in 20mm mdpe, the flow rate will be reduced to whatever the flow at 4 bar through 20mm is?

As JohnD said - that's not how it works. You can increase the pipe diameter at any point in the run to reduce resistance and improve flow.

Iknowcraig · 31 Oct 2018

fezster said:
As JohnD said - that's not how it works. You can increase the pipe diameter at any point in the run to reduce resistance and improve flow.

Thanks for this, so if I were to attach my new 32mm to the 20mm at the edge of my property I may find this improves the flow? I might give this a go before shelling out the £2k and see what I think!

John D v2.0 · 31 Oct 2018

Iknowcraig said:
Thanks for this, so if I were to attach my new 32mm to the 20mm at the edge of my property I may find this improves the flow? I might give this a go before shelling out the £2k and see what I think!

They would be my recommendation, you have nothing to lose!

Dan Robinson · 31 Oct 2018

Water is not compressible. Any significant restriction at the beginning of the run will ruing performance downstream.

OP beware of DIY advisors.

fezster · 1 Nov 2018

Dan Robinson said:
Water is not compressible. Any significant restriction at the beginning of the run will ruing performance downstream.

OP beware of DIY advisors.

Really? Do you think it makes any difference if the severe restriction is at the beginning or the end of the pipe run?

Edit - fixed typo make to makes

John D v2.0 · 1 Nov 2018

If the op or anyone else ls in doubt about basic physics they can easily check for themselves

Dan Robinson · 1 Nov 2018

Indeed

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£2k for water main upgrade, other options?

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