Heard of pipes shrinking?

Ging Ging

Hey got a shock a while ago while doing a job in the city centre.
Basically I had to find a major leak on a heating system in a basement. The pipework had been in about 15 years or so and was lagged qualpex or similar and about 4 inches beneath concrete.
I dug a hole exposed four seperate 1 inch pipes and cut them so I could isolate different sections and test for a leak.
As soon as I cut them the ends sprang apart between 20 and 30mm whereas they should really have remained in position. One didnt move, but after a bit more digging I found it had already pulled 40mm out of a fully compressed 318 tee:eek:. That was the leak funilly enough.
So the pex pipe had undergone considerable shrinkage since it was installed. Not sure of the manufacturer as I couldnt see any printed on the exposed sections. Has anyone else encountered this, I could do without it. Thankfully this time the pipe run was uncomplicated so could be narrowed down but could just imagine digging holes all over the places gofer style.

Outkast_IRE

well as you said its in a basement perhaps some sort of shift is occuring where the pipes are buried wether it be settlement of foundations or whatever , never heard of shrinkage to that extent but , have seen qualpex pull out of tightened fittings after being buried underground and a good period of time passing .

Its rare but it does happen , one particular job i was on the heating was pressure tested to 6 bar for 7 days which it passed no problem , pipes were then buried while pressure test was kept on, was fine for over 18 months then major leak on a buried pipe , the qualpex had pulled out of the joint . Happens every now and then incredibly rarely thankfully all you can do is ensure joints are properly compressed etc.

yoshytoshy

I've heard of some systems piped completely in qualpex (older type) ,which have somehow become porous.
Bascially the systems are completely filthy and air is getting in through the piping.

I don't use qualpex myself ,but a lot of new builds are 100% pex.

Outkast_IRE

yoshytoshy wrote: »

I've heard of some systems piped completely in qualpex (older type) ,which have somehow become pourous.
Bascially the systems are completely filthy and air is getting in through the piping.

I don't use qualpex myself ,but a lot of new builds are 100% pex.

The reason the older type qualpex systems leave in air is because that generation of pipe did not have a oxegen barrier encorprated into the pipe . So really it should never of been used for heating in the first place , but thats the benefit of hindsight i guess. The current qualpex does have a oxegen barrier so this air infiltration shouldnt happen through the walls of the pipe.
Nothin wrong with using qualpex but id use copper anywhere i could such as hotpress , radiator pipes or anywhere on display.