The House Projects Thread

[Simon]

I'd go with 22mm for now - you never know what'll happen to the internal pipework in future. 25mm seems overkill though and I've never seen a rising main in that size internally.

Most new builds are 25mm blue mdpe incoming main now

I stand corrected.

[Jobbo]

Go 25mm MDPE. It's future-proofed then. It's all about maximising flow.

What Mike says. The pressure will be the same whichever size you choose; the volume flow rate is what is limited by the size of the pipe.

We have a 15mm supply pipe and while it's fine for a good shower, flow drops off when someone flushes a loo elsewhere. I'm definitely putting in the largest diameter supply pipe I can when we start works.

FWIW, the cross sectional area of a 22mm pipe is 2.15x that of a 15mm pipe; a 25mm pipe is 2.78x the area. In a smaller pipe the boundary layer has a greater effect too; with a 25mm supply pipe you will be able to get three showers running simultaneously at the same flow rate as one with the 15mm supply.

[Swervin_Mervin]

Go 25mm MDPE. It's future-proofed then. It's all about maximising flow.

What Mike says. The pressure will be the same whichever size you choose; the volume flow rate is what is limited by the size of the pipe.

We have a 15mm supply pipe and while it's fine for a good shower, flow drops off when someone flushes a loo elsewhere. I'm definitely putting in the largest diameter supply pipe I can when we start works.

FWIW, the cross sectional area of a 22mm pipe is 2.15x that of a 15mm pipe; a 25mm pipe is 2.78x the area. In a smaller pipe the boundary layer has a greater effect too; with a 25mm supply pipe you will be able to get three showers running simultaneously at the same flow rate as one with the 15mm supply.

You going for a 32mm MDPE then?

My parents' place has 25mm and will happily run 2 showers at full tilt and someone can wash up, all off a WB 42CDi Combi. Ours hasn't changed much at all since switching to the 25mm MDPE supply but I'm hoping that's all down to the internal pipework and the far too small combi.

[GG.]

Ours hasn't changed much at all since switching to the 25mm MDPE supply but I'm hoping that's all down to the internal pipework and the far too small combi.

This is the root of my question - I know a larger diameter pipe will provide better flow if it splits or feeds into several smaller ones for example but if the whole thing is strangled by it feeding directly into a stopcock and then 15mm copper I'm sceptical as to whether it will make a difference.

Obviously it would future proof the system but I'm not sure realistically that we're going to rip out all the pipework after the main stopcock/upstairs to remove that bottleneck. I've seen some references online to the larger pipe acting as a "reservoir" but that would seem more relevant to pressure difficulties rather than flow. Our system is approx 10l/min so could be better but not abysmal - pressure will drop in the shower if a toilet is flushed or other taps run, as with Jobbo's house.

The only reason I'm not just telling him to go with 32mm MDPE (which would be my normal approach as I hate coming back to something which could have been sorted properly the first time) is that we have tight access at certain points on the new route we have to take to avoid digging up the concrete sub-floor of the kitchen. If I order x metres of 25mm MDPE and he can't get it fitted that would be most annoying!

Thanks v much for the input everyone.

[Jobbo]

You going for a 32mm MDPE then?

My parents' place has 25mm and will happily run 2 showers at full tilt and someone can wash up, all off a WB 42CDi Combi. Ours hasn't changed much at all since switching to the 25mm MDPE supply but I'm hoping that's all down to the internal pipework and the far too small combi.

Haven't specced it yet - I doubt the cost of the pipe is going to make any difference so perhaps! 25mm looks more than adequate though; we almost certainly won't have more than 3 showers in the house even if we do a loft conversion.

[Swervin_Mervin]

Ours hasn't changed much at all since switching to the 25mm MDPE supply but I'm hoping that's all down to the internal pipework and the far too small combi.

This is the root of my question - I know a larger diameter pipe will provide better flow if it splits or feeds into several smaller ones for example but if the whole thing is strangled by it feeding directly into a stopcock and then 15mm copper I'm sceptical as to whether it will make a difference.

Obviously it would future proof the system but I'm not sure realistically that we're going to rip out all the pipework after the main stopcock/upstairs to remove that bottleneck. I've seen some references online to the larger pipe acting as a "reservoir" but that would seem more relevant to pressure difficulties rather than flow. Our system is approx 10l/min so could be better but not abysmal - pressure will drop in the shower if a toilet is flushed or other taps run, as with Jobbo's house.

The only reason I'm not just telling him to go with 32mm MDPE (which would be my normal approach as I hate coming back to something which could have been sorted properly the first time) is that we have tight access at certain points on the new route we have to take to avoid digging up the concrete sub-floor of the kitchen. If I order x metres of 25mm MDPE and he can't get it fitted that would be most annoying!

Thanks v much for the input everyone.

As Jobbo says though, the cost of the pipe will be pennies, so may as well have it imo. 25mm that is. Is he proposing to mole it in?

10l/min is pretty poor for a bigger house tbh. The bigger combi's are capable of pushing out hot water at over 20l/min. I think my parents CD42 does 15l/min. That might not sound like much more but it makes a very big difference trust me, as our lowly 28cdi will only do 11l/min and one reasonable shower is its limit.

[GG.]

No its going under the suspended floor through the hallway and dining room and then there's a drop down several steps to the kitchen at which point it is going to feed behind the kitchen cabinets at floor level. Its this part that had him nervous about the diameter of the pipe, particularly given it will need to do a 90deg at the end of the run in order to turn back up behind the undersink cabinet to attach to the old stopcock.

We're only a three bed two bathroom terrace though and its unlikely both showers will be running simultaneously so it doesn't irritate me overly at present. The flow is probably still better that the previous flat in a victorian conversion that we owned! I'd need to check but think our boiler is only probably a 30cdi.

I think 22mm plastic barrier pipe is the minimum I'd want to risk really. Probably also rather the barrier pipe than the MDPE as well given it isn't being buried (though given we're current imbibing lead infused water anything is going to be an improvement!).

[JLv3.0]

suspended floor

NO.

Raised floor.
Suspended ceiling.

[Swervin_Mervin]

No its going under the suspended floor through the hallway and dining room and then there's a drop down several steps to the kitchen at which point it is going to feed behind the kitchen cabinets at floor level. Its this part that had him nervous about the diameter of the pipe, particularly given it will need to do a 90deg at the end of the run in order to turn back up behind the undersink cabinet to attach to the old stopcock.

Seems an unusual solution!

Have you had a quote to mole it? Ours was £750, including internal connection.

[Rich B]

suspended floor

NO.

Raised floor.
Suspended ceiling.

Ummm, is suspended not the correct term for a timber floor on joists that are suspended between suppprting walls?

[ste]

It's how I've always heard it referred too. *shrug*

[Simon]

Indeed. In my parent's 1930s house the floor is on joists which are suspended across brick pillars under the floor.

[JLv3.0]

Oh yeah that does sound right actually - good thing I don't work in construction! Erm......

[GG.]

I don't work in construction!

Isn't this technically true right at the moment

[JLv3.0]

No mate I've been working since last November.

[GG.]

In that case congrats on the new job!

[JLv3.0]

Thanks GG but it's only some freelance work - claims which I hate but it's easy, good money and the appointments (finished the first phase of it late December, two more months work now awarded) have just landed in my lap without me having to chase them so I can't really complain. I mean - I do, but it's not worth listening to

I don't want a grown-up full time job right now - I can't really be bothered with it.

[Jobbo]

Planning application was sent off on Saturday by our architect. I don't anticipate any hurdles so we should get consent without having to alter anything. Not sure whether we'll be starting the work this year; I suspect it'll be more sensible to do it next spring/summer.

[Rich B]

Planning application was sent off on Saturday by our architect. I don't anticipate any hurdles so we should get consent without having to alter anything. Not sure whether we'll be starting the work this year; I suspect it'll be more sensible to do it next spring/summer.

which option did you go with?

[GG.]

Planning application was sent off on Saturday by our architect. I don't anticipate any hurdles so we should get consent without having to alter anything. Not sure whether we'll be starting the work this year; I suspect it'll be more sensible to do it next spring/summer.

which option did you go with?

And did you spec "man loitering by back door"?