Compression or capillary joints

[Tin Gill]

Hope there's a plumbing expert out there who can help!

I've heard that compression joints shouldn't be used underneath floorboards or where they can't be reached easily as they aren't as reliable as capillary joints. Is this true?

I've used loads of compression joints fitting a new bath but am a bit worried I should have used soldered capillary joints. Anyone, any ideas?

Thanks.

 

[Scoby_Beasley]

I'm no expert but personally prefer capillary over compression especially in those tight corners you cant quite get to and tighten the comp nuts up enough.
Having said that if you can do a comp up tight enough you shouldnt have problems.

 

[keyplayer]

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[breezer]

sorry if you know this. but you should clean the outside of the pipe and the inside of the joint with wire wool, then smear flux on it first , put joint and pipe together and heat with blowtorch

 

[Tin Gill]

Thanks guys...do compression joints 'deteriorate' after a while or is that just a myth?

 

[breezer]

never had one go, they have been known to come ever so slightly loose, but its out with the spanners to tighten them up, but thats one thing you can't do with soldered joints, you have to drain the whole lot to re solder them

 

[Scoby_Beasley]

The only downside I know of with comp joints is if you need to remove one (say, changing a sink) you can't get the olive off and the pipe needs to be replaced. BUT If this happens, you get some hemp (unravelled string), wrap it round like you would p.t.f.e. tape on the screw threads and then put GLOSS/OIL BASED paint on it, tighten up and give it half an hour. Believe me, it works.

 

[breezer]

yes you can take the olive off, put a junior hacksaw through it, fiddley but it can be done

 

[masona]

The biggest problem with compression joints is when it's overtighten.If you're worried then put some White Halk compound on the olive ring and just hand tight the nut.They are 100% reliable if done correctly.

 

[BFG]

I go for pre-soldered capilliary. I thought I was cheating, until I spoke to a lot of plumbers recently looking for boiler technical advice.

Almost to a man they recommended plastic tube with push fittings. Suitable for mains, central heating etc. I was amazed.

Haven't tried it yet, but I keep an open mind.

 

[tazkb]

plastic pushfit are every diy dream and make the whole job a piece of cake just remember to use the inserts in the ends of the plastic pipe and make shure you push the pipe fully into the sockets i now only use pushfit fittings they are brilliant

 

[ChrisR]

Yes compression joints can come loose particularly if used on hot pipes due to the constant movement. Water regulations preclude their use in inaccessible areas such as under floors.

Life expectancies on push-fit are not known. How long would you expect a rubber "O" ring to last?

Endfeed capillary joints can fail dramatically, soon or years later, if poorly made. Solder-ring capillary joints are easier to make more reliably. Heat should should be concentrated on the fitting not the pipe.

Cleanliness is key, as is getting the amount of heat right. Beginners are apt to overheat things so the solder doesn't stick. With a solder-ring fitting you stop when you see the solder appear, so it's easier to get it right.

 

[Tin Gill]

I guess it all comes down to personal preference...having said that I've now finished all the piping in the bathroom and with that behind me I think pre-soldered joints are the best of the bunch. I found that with the compression joints, if you move them too much once you've fitted them, they seem to work loose or are actually quite tricky to get watertight and there's always that nagging doubt that they might come loose once the floor tiles have been laid! Then again, I guess if I was a professional, I would have fitted them right first time!

Soldering joints might sound a bit tricky for an amateur but after wasting a few practicing, they're not too bad and none of the ones I fitted leaked at all. Compression joints sound easier but turn out to be a bigger pain than anticipated!

Also they're an awful lot cheaper!

 

[corgiman]

not allowed to use compression joints for gas if that are not readily accessable ie under floors!!

used them plenty of times for water pipes thou

 

[ChrisR]

As I said, similar rules apply to water pipes.
This is a DIY forum so I donlt think giving advice on how to do gas piping is sensible. DIY'ers are unlikely to have a guage or know how to test for leaks - more to it than it might appear.