http://www.isco-pipe.com/resource-center/faqask-a-question.aspx

PVC is horrible for dock usage, people use it around here when the original copper or galvanize is no longer any good. Higher winds and lower temps on the water cause things to freeze sooner in the year. any dock work i have done includes a drain line with a valve ran down to help get all of the water out. If i am working on an irrigation system i simply winterize the dock lines when i am doing the pump, all of the clients i service have garden hose laying around i simply run to the dock lines.

 

I think that you should do the test and give us the results.

 

Yes, it does break. PM me if you have any questions about winterizing in this region.

 

I went to a course in HDPE a while ago, and it's my understanding that properly fused, freeze does not affect it. Now with the 160, I can't remember, nor do I have any files on board. Worth checking with the manufacturer or supplier.

 

OK, here's what I do know: October, year before last, I ran a line like this under my dock.
350 feet 3/4" Cresline 160 PSI. The first 200' trenched in underground to get to the dock, then 145 feet under the dock (exposed to the air, but under the dock boards). Have only 1 fitting - a 90 degree barbed fitting threaded on the other end for the brass hose bib.
I tried to get a downhill run on it and I drained it both the past 2 winters, BUT you know how hard it is to get ALL the water out.
That pipe went thru the past 2 winters without breaking, including one spell last winter when the saltwater creek stayed frozen for 2 weeks straight.
So, it certainly appears to work and is far better than PVC, which is a joke in my opinion for an exposed dock pipe (but everyone here uses it).
But, I'm now re-doing the PVC water line on the dock at my work (which has broken - split in multiple places - each of the same past 2 winters).
What I'm really trying to find out is if the poly pipe can freeze and thaw without splitting? I don't know if my personal dock line did that or not, since I tried to drain it.

One more question while I'm at it - any idea how long this line will last if it is in the sun?
It is going to be hard to run it under the dock like I did the first one.

 

Very few of us know much about that pipe, it might be u.v. resistant, it is a type of poly, after all. As I said, check with the locals, google HDPE also.

 

From the following site, supplied by Mjtrole:
http://www.isco-pipe.com/resource-center/faqask-a-question.aspx

Comes this answer:

Will HDPE pipe freeze?
PVC pipe has a crystalline temperature of 32 degrees F, at which point it becomes as brittle as glass. HDPE pipe has a crystalline temperature of - 180 degrees F, which translates into less potential for failure. In fact, water can freeze & thaw repeatedly inside of HDPE pipe, without causing permanent damage to the pipe.

Thanks to Mjtrole for the information.:clapping:

My own research had only uncovered statements like "highly resistant to freeze damage" - sounds like a lawyer will not let them say it won't break.

I'll take the -180 degrees any day. If it gets that cold outside here, I have lots bigger things to worry about!!!

 

If you want freeze-proof you would look at polybutylene tubing, but it can have its own problems aside from freezing

 

Thanks Wet Boots. If it breaks, I'll try the polybutylene. I got a PM from Stuttering Stan that told me he had seen the poly pipes split in the extremely hard winter we had here this year, so apparently it IS possible for poly to freeze break. I have drains at the low points, so hopefully that and the greater freeze resistance than PVC will be enough.

I want to thank everyone for their help.