Chasing 10mm plastic central heating pipes into the wall

[Chris Skrimshire]

My son has just moved into an old house and wants to hide some radiator pipes by chasing them into the wall. The thinking is 10mm., for smaller channels, and plastic for simplicity and less heat loss.

I've never used or worked with plastic pipes so the questions I have are:-

Is plastic accepted now as being reliable, if so what makes are/are not recommended? I was looking at the HEP20 website, but have heard negative views of them in the past.

Are there radiator fittings/adaptors for 10mm plastic pipes that look OK?

Is it best to insulate plastic pipes or is this unnecessary?

Should the plastic pipes be in some sort of conduit or covering?

How deep/wide a cut channel (into brick, not breeze block) can we get away with?

I'm guessing that with plastic pipes some sort of metal tape would be a good idea so the pipe channel could be detected?

I'm assuming that chasing out channels (in the main living room) will be very messy (never done it myself). Any tips/advice on the best way of tackling it?

What are the chances of plastering over the channel without unevenness or cracking?

Any views or experiences would be very useful. Thanks.

Chris

[Owain Lastname]

Plaster on the hard, or lath and plaster? Lath and plaster doesn't chase and fill neatly as you cut through the laths.

On the other hand, it may be possible to go behind the laths, but watch for heat loss in the cavity.

Owain

[Murmansk]

I'd have thought it would look better if you were to join the 10mm plastic pipes to 15mm copper a few inches from the radiators

[nothanks]

My son managed to drill through a plastic pipe that someone had buried in a wall. He'd checked with a pipe/stud/cable finder but that didn't show anything. If I was burying plastic in plaster I would put something over it.

[Andrew]

You can get plastic coated 10mm copper tubing in a roll.

I bought 3 rolls for £10 when some numpty B&Q employee accidentally reduced the wrong product :-)

[David]

I would go with the John Guest ones. Easier to take apart again if you need to. The ones with metal teeth are a bugger to deal with IMHO.

Perhaps consider replacing the skirting boards and hide the pipes behind? Easier than chasing out walls then making good.

Remember that the 10mm is the external diameter. Plastic pipes have thicker walls than copper pipes so you get less water flow because the hole in the middle is less. This may not be an issue depending on the installation.

Unless you have solid floors it might pay off in the long run to run the pipes under the floor. I assume that the rest of the pipes are copper? Where do they run? I have vast experience of "That is too much trouble and disruption, let's just.....". But not in a good way.

HTH

Dave R

[alan_m]

More reliable if no joints inside your buried pipework.

Is the pipework coming down from the ceiling or up from the floor? Is the channelling to individual radiators or just for the runs that go floor to ceiling just to run the pipes between floors?

In old houses you may find that the plaster is 10+mm thick so you may get away with not having to channel out the brick too deep.

Some internal walls may be lathe and plaster - you may/will have other problems channelling this out. As soon as you cut through a lathe you will have unsupported plasterwork. If lathe and plaster you may be able to feed a flexible plastic pipe down from the floor above or loft down the cavity and cutting holes in the wall where you need to get through horizontal noggins or to gain access to the final end of pipe.

Before you install anything in the chasing channel thoroughly soak/paint it with a 50:50 PVA:water mix and let it dry. This will seal porous brick and existing porous plaster from almost instantly sucking out the water from your filling material. It's the quick removal of the water from new plaster in the chasing that will cause it to crack. Before filling the chase with new plaster again paint it with a PVA:water mix and let it go tacky.

Also, fill as a two stage process- perhaps use a bonding plaster first and leave 1mm to the existing plaster surface. Maybe then use a jointing filler for the final 1mm. Jointing filler is much easier to sand than plaster.

Maybe use the jointing compound for the whole fill in two/three coats but if you have a lot of chasing to fill it could become expensive. Bonding plaster is less than £10 for 25kg).

What may cause a cracking problem is the expansion of the pipe when hot so maybe fitting some form of loose cover over the pipe before plastering may be beneficial.

This link may work (without jumping through sign-in hoops) for chasing methods

[RJH]

Yes, that's what I did with several radiators, looping the pipe behind skirting under the floors. Works well - if you have suspended timber floors.

[Chris Hogg]

When the DHW and CH systems were replaced in my bungalow, I asked for the pipes to be run around in the loft with fall-pipes chased into the walls. Much air sucking through clenched teeth from the plumber! He said the expansion and contraction would crack the plaster. I insisted I didn't want the piping visible, so eventually he chased it into the solid concrete floor.

The plumber installed PEX pipe everywhere, aluminium pipe coated inside and out with HD polyethylene such as this

and push-fit connections.

All OK so far, three years later.

[Brian Gaff (Sofa]

Be a nightmare to sort out a leak though, what about below the floor? Brian

[Tricky Dicky]

Daughters house is a new build with dot and dab drywall throughout. All the pipes to the downstairs radiators are plastic and drop down from the ceiling. The pairs of plastic pipes emerge out of electrical back boxes with a special cover that tends to bend the pipes outward, these exit points are hidden behind the radiators and you can just about see them as they enter the valves using a 90deg bend. When my daughter moved in she was told by the builders representative that the location of the pipes could be found with the likes of a stud detector set for metal as the pipes were covered with a foil type insulation.

Richard

[Dave Plowman (News]

More reliable than copper? Not sure plastic has been around long enough to say that. I've got copper in this house over 60 years old.

[Andrew]

I thought all 'plastic' pipes for central heating had a metal oxygen barrier as part of their construction ?. You can see it after cutting a pipe (not with a hacksaw though :-) )

[Andrew]

Women don't care about minor details like after-maintenance, they have an aversion to exposed pipes.

Andrew

[alan_m]

I meant that a join or fitting is more likely to leak so try and avoiod buried joins

This year I've had 30(ish) year old copper develop a pin hole leak - luckily under the suspended ground floor void.

[Nick Cat]

I presume you've worked out that 10mm is big enough for some rads. It's usually not enough for all CH piping. Burying iron wire with it makes it traceable. You'll need to use barrier pipe, it blocks O2 diffusion. Pipes expand & contract with thermal cycles. Pushfit, and to a lesser extent other types, come undone with enough such cycling if the pipe isn't free to move. Wrap with denso tape or anything else that lets it all move.

NT

[alan_m]

15mm copper is not always enough.

IMO it would be very unwise to change the inside diameter of the pipes already in situ. As others have said, 10mm is the outside diameter not the inside diameter, which also will be reduced when using inserts for joins.

JG Speedfit give a figure of 1% expansion on length between the temperatures 20 to 82C. That could be a 24mm (approx 1 inch) expansion on a floor to ceiling run. Copper would be more like 2mm on the same length of run over the same temperature difference.

[Dave Plowman (News]

Can't say I've seen a domestic rad that doesn't take the standard 1/2" gate valves, etc?

[alan_m]

The OP hasn't indicated which pipes are to be buried. If it's just a short pipe to a single radiator then it may be feasible but if its anything like my installation floor with ceilings runs (and much of the underfloor) in 22mm copper it's likely to result in non-working CH system if replaced with 10mm plastic. My boiler input/output are 28mm fittings, albeit reduced to 22mm copper for the pipes.