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Expansion joint for PVC?

Author: Learning2 (NC)

I want to run a 110' straight line of 3/4" PVC under a dock. Fastened to the joists. But there is 2" of thermal expansion per 100 feet per 50 degree change in temp. 110' 0" becomes 110' 2".

For electrical PVC conduit they make plenty of expansion joints for this purpose - because they often come from 2-3 feet underground to above ground. And I see expansion joints for PVC DWV also. Of course neither are under pressure.

Do they make an expansion joint to meet my need? I have used expansion repair couplings before but I doubt they are meant for routine, long-term expanding/contracting. I figure they are meant to be installed and pretty much stay in one place.

Or maybe I need a different idea altogether?

Thanks!

Re: Expansion joint for PVC?
Author: Learning2 (NC) I found that Spears Manufacturing makes an expansion joint. In either 6 inch or 12 inch travel. But $250!!! There must be another way. What is it?

Re: Expansion joint for PVC?

Author: bernabeu (SC)

leave this fitting in an accessable 'box'
see: [www.plumbingsupply.com]

else:

you will need to have a 'expansion loop' in the line (from your description about 36" x 12" x 36")

only the ends should be 'anchored', all other 'straps' / 'hangers' should allow pipe movement

see: [www.bing.com]

- - - - - - -

Measure twice, cut once.

Retired Plumbers Local Union #1

Edited 2 times.

Re: Expansion joint for PVC?
Author: Learning2 (NC) I did not think the expandable repair coupling you mentioned was intended for long term expansion / contraction. Which is why I was looking for another solution.

Re: Expansion joint for PVC?
Author: bernabeu (SC) i gave the other option .... an 'engineered' hard piped expansion loop .... see link under pic or spend $250 .... either way you will still need straps/hangers/supports which permit the expansion movement w/o binding - - - - - - - Measure twice, cut once. Retired Plumbers Local Union #1

Re: Expansion joint for PVC?
Author: hj Four elbows in a "U" shape is all the expansion loop you need.

Re: Expansion joint for PVC?
Author: Learning2 (NC) Would I be better off using PE pipe - the kind used outside to bring, for example, water into the house from a well? Would it be more forgiving?

Re: Expansion joint for PVC?
Author: hj If you "snake" it.

Re: Expansion joint for PVC?
Author: jblanche (WI) How about using the PE pipe with a 360 loop? I am not sure what hj means by snaking. ***************************** Links to the State of Wisconsin Plumbing Code: [dsps.wi.gov] *************************** I am not a plumber. *****************************

Re: Expansion joint for PVC?
Author: hj zig zag it rather than going straight. This allows for both expansion and contraction.

Re: Expansion joint for PVC?
Author: North Carolina Plumber (NC) You would be much better off using PE pipe.

Re: Expansion joint for PVC?
Author: Learning2 (NC) Why do you recommend PE pipe?