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Replumbing whole house with Speedfix?

Postby Chick21 » Mon Feb 21, 2011 9:58 am

Bear with me, I am currently looking at replumbing the whole house with JG Speedfit and plastic pipes as a DIY job. I am replacing all the radiators in the house, and need to remove all the original pipework (which is above the floorboards and relay them below the floorboards and drill holes through the joists (all doable on the upstairs floors, just need to figure out the best method downstairs (concrete floor).

Basically I'm keeping the length of copper from the boiler, then refitting from there on. Does anyone have a simple plumbing diagram I could follow? I was thinking of using 22mm from the boiler to upstairs and downstairs and then splitting down to 15mm for the radiators.

One of my friends says on his current project the contractor is using speedfit and plastic pipes around the whole house!

What are people's opinions of this and should I even attempt to do this myself?
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Postby htg engineer » Mon Feb 21, 2011 6:45 pm

Personally I do not use pushfi /speedfit, as it is, and does look like a DIY installation.

You really need 22mm flow and returns from the boiler as far as you can, then reduce down to 15mm or 10mm.

The best way for downstairs, is to put trunking/capping up (or chase the wall) from ceiling to skirting, run pipes underfloors upstairs and through ceiling into trunking then run the plastic pipe down to skirting level and fit a plastic/copper elbow, from the capping/trunking to the radiator valve I would use copper - for aesthetic reasons.

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Postby stoneyboy » Mon Feb 21, 2011 7:03 pm

"I was thinking of using 22mm from the boiler to upstairs and downstairs and then splitting down to 15mm for the radiators" - Yes should be OK but look out for any variation to this in the existing system.
I am still dubious about the long term dependability when using plastic pipe inside a house especially on a hot water system. The joints rely on one 'O' ring for sealing and on the installer to fit a metal insert. Too much risk!
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Postby plumbbob » Sat Feb 26, 2011 12:54 pm

Ok, so here's a post from someone in favour of plastic pipe.

About five years ago I was "initiated" into the world of plastic pipework. Up until then I had always used copper for everything spending hours bending pipes and soldering fittings to ensure they looked neat and professional. I refused to even to use flexible tap tails supplied with some taps.

Now I use it all the time. It has so many advantages over copper. It doesn't corrode, scale up or burst if frozen. It is easier to install and you can shove it in places you'd never get copper to go. You can bury it in concrete or run long lengths without joints.

Don't get me wrong, I still use a lot of copper. Always where the installation might be at risk of damage and especially where visible as its neatness is essential.

Many experienced tradesmen steer clear of plastic for a variety of reasons and I respect their decision especially as some of the points are very valid. Having said that, there is a saying, don't knock it until you've tried it and I think once you have tried it, you'll find it is very difficult to knock it.
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Postby jimbob22 » Sat Feb 26, 2011 11:32 pm

Dear, dear . . . 'tis a conundrum this old vs new, isn't it ?

White plastic might not be much cheaper overall due to potential cost of connectors, or last as long as copper but today it looks just fine as supply in modern kitchens and bathrooms, and also, with the barrier pipe for central heating and hot water, has a lot of advantages, esp in reducing installation time.

Just remember to keep the first 100cm of the pipework from, and to, the boiler in copper and keep all the plastic pipe away from any local hot-spots.

Oh, and remember not to mix up pipe inserts from other manufacturers, whether using push-fit or brass compression connectors.

With more than twenty years experience of plastic pipe, I can testify to its general longevity, but have seen a few connectors split or o-rings leak and even snap-rings fail and, whilst those events have, thankfully, not been as frequent as seeing some plastic lock-nuts back-off completely, so I now almost always use brass compression fittings on barrier pipe, preferably with stainless steel inserts and light brass or copper olives - AND they're cheaper, esp in bulk, and last for life ! ! !

But do, always, use three, or so, wraps of ptfe tape on threads 'cos, although the olive should make the seal, with thread and other tolerances not being what they used to be, the tape should help take up any slack.

Better still, fit a PRV for £30 and set your rising main to 2bars and never change a leaking ball-cock again!! Might need to fine-tune final pressure setting to ensure flow is maintained to thermostatic showers, boiler, etc. Also consider a 22m tee, with a stop-cock, to the garden and garage after the double NRV and before the PRV.

As Plumbob mentioned, 15mm copper (or chromed, or snap-covered) pipe (or steel-braided flexibles), to the radiators, are the most pleasing, lookswise (esp laquered polished copper and timber) and mechanically, but unfortunately if hooking up to a mainly plastic system, requires the introduction of an extra connector and, therefore, another potential leak-path, something all designs should seek to minimise...

The alternative, the use of plastic all the way to and from the rads should, at least, result in lesser maintenance.

The great things about coiled plastic are the lack of joints required and the ability to be cabled through joists, etc, and to be bent.
You can't bend it as much as copper.
If trying for a tight radius, ALWAYS USE A PIPE BEND SUPPORT , of the proper diameter and DON'T baulk at the cost - always think long-term (and let the client know why things may seem expensive to install but will pay off ....).

It's better to use pipe snips for a clean square cut and try to give the vertical (or horizontal) rad tail section as long and straight an entry into the rad valve (squarely through the compression olive to the stop) and increase the chances of a long-lasting seal.
A bend supports may help achieve this, is slim and is easlly tacked to a joist, etc.

Olives are best on copper and also give a better grip on barrier pipe than grip-rings - but do remember to keep tightening slowly until it sqeaks three times ! (try it) That way the inner and outer tubing seal around the insert and the olive compresses fractionally and bites in to provide grip on the outer barrier layer.
Use ptfe or Boss on the threads but never on the olive (unless it's a life-saving bodge !)

Think about using a simple (bit pricey, but might pay vs call-outs) centrifugal-type filter (eg Sentinel, Fernox, Magnaclean) to protect the pump(s), valves and esp the boiler, a no-brainer if you're hooking into an existing system, esp after the flushing out, even with plastic pipe there is scale build-up : it comes from the boiler and the steel radiators.
Fit the filter on on the return 22mm line before the pump and look for one with a built-in dosing point (or create one).

Also, try to optimise drainage points, an extra one or two may help but again balance against adding new leaks, Access for future inspection and/or maintenance can sometimes help decide.

Do also remember to further increase efficiency of the installation by foam insulating ALL pipes and clip the lagged pipe (in bundles if necessary) to avoid cold breaks, worth the few minutes extra :D
Don't forget that condensate outflows should be sealed to the drain or trap and insulated with an outer pipe.

Happy Piping ! !
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