Black plastic Water pipe - what is it?

[Gordon Henderson]

Another daft question, (thanks for all the screwfix shop replies - works a treat!), but the incoming mains to our house is a black semi-flexible pipe of about an inch in external diameter. This has what looks like an odd coupling that looks like some sort of compression joint to 15mm pipe where I fitted a stop c*ck some years back... (works fine).

Our water pressure is high (8 bar), but flow rate low (under 10 litres a minute) I think due to some external restriction in the pipe work - which I'm not prepared to dig up at this point in time.

I'd like to remove the join to the 15mm pipe, fit a coupler to 22mm pipe, a quarter turn full-bore "stop c*ck" to make it fool-proof for wifey, then fit a pressure reducer to 3.5 bar, and then run 22mm pipe from there - hoping to get a better flow rate at a pressure that'll reduce the possibility of burst pipes (not a plesant sight round here when it happens - as it did to our neighbours recently)

Googling finds various names for plastic pipe - mostly seem to refer to blue alcathene or MDPE pipe, but I'm not sure that's what I have. It's black!

So can some kind soul tell me the name/official size of the pipe and suggest a coupling device?

Thanks,

Gordon

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Gordon Henderson saying something like:

It will probably be black alkathene - is it thick-walled, ie, 1/2" bore in a 3/4" outer diameter, or metric equiv? The thin-walled stuff is commonly used by farmers for shed and field cold water supply. If thick-walled, you can simply treat it like copper pipe and use a normal compression fitting on it, tightened well. I have a 150psi mains supply with a compression fitting on it that's survived a decade like that.

[<me9]

Got same, 1/2"(bore) alkathene pipe -- the norm in the 60s/70s before the (metric) blue took over

Hmm I've 2.5bar, and similar, possibly higher, flow rate. Approx 15metre run of 1/2" alkathene.

I thought of upgrading internally to larger pipe but decided it was a waxte of time with the pressure and flow I had. In you case I'd estimate teh length of black alkathene and see if it is that causing the low flow or an obstruction upstream.

BES will do something suitable It is 21.5mm external, and will fit a 22mm compression with suitable 3/4" olive (and possibly pipe stiffener but pipe wall is thick).

[BigWallop]

Is the pipe plastic, or are you looking at an old lead pipe? Lead can feel, look and act like plastic in some cases, and the coupling you talk about could be a lead to copper fitting which was used when the solder wipe joint was outlawed back in the eighties, early ninties.

So look at the black pipe again and gently scrape the outside of it with a small blade to make absolutely sure that it is what you think it is.

..

[Gordon Henderson]

So... Thanks for the replies...

Proper investigation has found the following:

It's plastic and black. Not lead - it bends easy and feels plasticy. Scraping the surface reveals more black plastic!

Outside diameter is very close to 20.5mm. Wall thickness hard to determine without cutting it, but it's fairly stiff to try to bend. (but it also has 8 bar inside it)

It could very probably be dated to the early 60's for initial installation.

So shouldn't be hard to get the right fitting now.

Cheers,

Gordon

[tinnews]

Are you sure it's not just standard black MDPE pipe for use above ground? It's identical (in dimensions) with the more common blue stuff but for use above ground.

[Tim S]

Gordon Henderson coughed up some electrons that declared:

Not daft - been there done that.

Mine was 1/2" black alkathene (phone call to water board who took a stab at identifying by description). As other's have said, yours is almost certainly the same.

I would say you have a restriction. I have 12-13m of that pipe at 7 bar and I can get 50+l/min out of it.

went via blue MDPE - not sure if that's your intention. Or do you want to go direct from 1/2" to copper 22mm?

If the former, I used

(part 11330) to go from 25mm MDPE to copper (don;t forget the pipe insert).

and 13544 on the same page to go from 1/2" to 25mm MDPE.

If going from 1/2" to copper I suspect you could just use the latter as it's rated for 22mm copper.

1/2" alkathene can be made off with a compression joint similar to 11330 above, but I'm not sure where you'd get one with the correct olive and insert.

Peglar 1/4 turn full bore valves are good - and for the pressure reducer I recommend

doesn't mess with the flow at all. I still get 50+ l/min through it at any pressure setting.

You'll need some gas PTFE (or a *lot* of water PTFE or some other potable threadlok type stuff) to seal the pressure dial on. For some sick reason they used parallel BSP threads and there's no seat to seal against - and if there were, you'd not get the dial in the right place.

Cheers

Tim

[Tim S]

[e-mail] coughed up some electrons that declared:

That's a point. My alkathene stuff has concentric rings on it - very faint but it's not smooth. If someone could confirm if black MDPE is as smooth as blue, then that would be one possible indicator.

Cheers

Tim

[Gordon Henderson]

It sounds now that that's exactly what it is.

Didn't realise it came in black though which is what put me off the scent earlier!

It (crudely IMO) comes out of the wall at ground level, is bent sharply upwards to fit in a narrow gap where the compression fitting to 15mm is, then the stop-c*ck and rest of house piping.

The plumbing in this house seems rather ... "creative" and I'm slowly trying to sort it out..

Thanks,

Gordon

[Gordon Henderson]

Going by other posts - it may be standard (modern) MDPE piping, but black rather than the usual blue...

More investigations earlier this evening found a crudded up stop c*ck outside the house, but on our land. We did get the waterboard to check the street valve and connection when we moved in. I think it's this external siezed up valve that's cusing the restriction. Don't have the means to dig it up right now though.

I've seen the results of a leak in a neighbours house...

What I was really after was moving the system to mains fed rather than tanks in the loft... The bath can fill quicker by gravity than the tanks can re-fill from the mains.

Thanks for the links - good reference though. I'll pull the dishwasher out tomorow (Which the pipe runs along the side of) and get a better look at it and see if there is any identifying marks and I'll be better able to size it then too.

Gordon

[RubberBiker]

From the description, size and your probable date - black alkathene.

I have exactly the same stuff.

I lopped off the naff transition fittings from various bodges down the years, and fitted an all-plastic MDPE stopcock (brilliant thing, light to turn and shuts off to the last drop).

fittings will go straight on - no pipe insert required.

[Tim S]

Gordon Henderson coughed up some electrons that declared:

On an aside -

I found these clips (so called hospital clips) to be very good for mounting the stopcock. They give an exceedingly solid mount and tight clamp to copper pipe:

6504

When I ran my new bit of MDPE into the house, however I rotate and tighten the fittings it always seems to develop a bit of torsional stress and these clips hold it solid.

Cheers

Tim

[BigWallop]

I think they're called hospital clips because they are fully enclosed, with no bits to gather dirt in crevasses and nooks, so easily cleaned with a wipe of a cloth.

(but don't quote me on it)..:-) ..