by 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 ! !