Poly Plumb piping sucks?

[whiteoaks7]

Anyone know if PolyPlumb piping (or plastic plumbing piping generally) works in a suction line? In this configuration the pressure inside the pipe will be lower than atmospheric so air will try to get in through the 'o' seal joints. It's probable that the system is designed such that internal pressure is required to push the 'o' seals against a sealing face - hence my question.

 

[philmayfield]

I've tried this with pneumatic airline pipe with similar o-ring push in connectors and yes, it did leak liquid pulled through by suction. I would imagine the Poly Plumb system would be similar.

Phil

 

[pete]

Most domestic plastic pipe systems can use there own push fit fittings or standard compression fittings (with the correct inserts)
You should be safe using compression fittings.
We only use plastic pipe marked "barrier" as the old none barrier plastic pipe could let oxygen pass through it into the pipework causing corrosion in central heating systems.

Pete

 

[Danny Jo]

I had the devil of a job getting my fresh water pumps (both hand and electric) to deliver any water to the galley sink. It wasn't until I took the filter unit out of the circuit that the penny dropped. The filter's feed and outlet connections were attached to the filter with O rings designed to prevent water getting out, not air getting in, and the filter was connected just below the hand pump. Air was getting in through the connection and back to the negative pressure side of the electric pump.

Mark

 

[tcm]

Polypipe and the assoc all-compresion fittings has designsuch that they compress a rubber o-ring against face whilst static so in othr words twill be fine in suction, i believe, tho not actually tried it.

You haveto make v sure that you havete little reinforcing inserts in all the ends of course, so you can screw tight the fittings, but hand tight is good enough. But not having the inserts means it leaks. I *have* tried this, tho not on purpose...

oh, yes, and whilst re-living a distant nightmare, be careful with the little metal grippy washers, as they won't come off once on the pipe...

 

[richardandtracy]

If you use the solvent weld stuff rather than the screw up compression fittings, then it can be. I'm using the solvent weld over-flow stuff (19mm pipe) in my garden as a syphon for distributing rainwater.

Regards

Richard.

 

[pappaecho]

I am assuming that you refer to 15mm polythene pipe used to replace 15 mm copper.
If you buy the stainless (13mm od inserts) and then use 15mm brass compression fittings, when you tighten up you get a 100% gas tight fit, because the olive bites slightly into the plastic. It also has the advantage that there are no rubber O rings which can be affected by oil, petrol, diesel etc.
I use such an arrangement to pump out diesel from inaccessible tanks.