Do Your Water Pipes Drain ????

[Flybob]

Originally Posted by checkmate99

I don't understand your reluctance to allow water to remain in the plumbing system between your camping trips. Since city water is chlorinated, no harm in leaving the water in the pipes while the unit is sitting.

The chlorine quickly dissipates and you will get nasty stuff growing in the plumbing. If you want to see for yourself. Fill a jar about 1/2 full of water from your chlorinated pipes cover and let it sit in your RV between trips. You will be amazed at what will grow in the jar.

[Thurman]

With all due respect to "pmsherman", post #20: PEX tubing will burst if water is allowed to freeze within the tubing. Many studies have been made and I have been fortunate to attend classes where computer made videos show what happens when water is allowed to freeze within different tubing/pipes. If you have ever seen a run of tubing or pipe that had split as a result of water freezing you have seen the split in the pipe and most people assume that at that point is where the freezing occurred. Not exactly so. A certain place within a run of tubing or pipe gets cold enough for the water to freeze. Once the freezing starts then a "plug" of ice will start to form within the walls of the tubing/pipe. As this plug grows it creates hydraulic pressure from both ends, no matter what is on the ends of the tubing/pipe. When enough hydraulic pressure is built up so that the pressure created exceeds the bursting strength of the tubing/pipe then the point of least resistance of the tubing/pipe will split/burst. Many tests have shown that this point could be near the plug of ice or could be many feet from the actual ice plug. All this is taking into consideration that the tubing/pipe is full of water. When one removes the standing water within an RV's water lines it would stand to reason that this eliminates the possibility of such a plug of frozen water would develop.

[oldtool2]

Originally Posted by pmsherman

As an aside, I've read that PEX pipe is rated to withstand water freezing inside it. I've never tried to verify this and, even if the pipe withstands the pressure from Ice forming inside it, I'd be concerned that the inexpensive compression fittings used at the end of the pipes would give way under that pressure then leak the following season.

Phil

I find that hard to believe.

I have never heard of any piping system that would / could not break. Water expands when it freezes. It is one of the few liquids that does and that pressure has got to go somewhere. Even soft copper will split.

Jim

[pmsherman]

Originally Posted by oldtool2

I find that hard to believe.

I have never heard of any piping system that would / could not break. Water expands when it freezes. It is one of the few liquids that does and that pressure has got to go somewhere. Even soft copper will split.

Jim

Small metal pipe is manufactured using two techniques. Almost all pipe is rolled from flat stock and welded where the ends come together. The weld is a weak spot that usually splits when freezing water expands inside it. (Actually, water contracts as it cools until it reaches 4C when it starts expanding.) Seamless pipe is made by passing a rod through rollers that squeeze it in different directions which opens up a hole in the middle of the pipe. Seamless pipe is much stronger than seam welded pipe and also is much more expensive.

PEX pipe is a plastic which is a lot more flexible than metal. Plastics do not have metal's rigid structure and can have the ability to stretch a little then return to their original size. The following quote is from Black Diamond Plumbing Supply's (Chicago) web site: "Due to its flexibility, PEX has a small margin of expansion under the damaging pressure caused by ice formation. If the weather gets cold enough, PEX pipes can and will freeze like any plumbing. However, PEX may be less likely to rupture as a result of freezing."

The effects of freezing water are obvious to anyone who drives in the northern parts of the US. Potholes arise from water getting into a crack in pavement, freezing and expanding with its resulting damage to the road material. Water freezing in a rock with a crack in it can split the rock, part of erosion of mountains.

Phil

[oldtool2]

Originally Posted by pmsherman

However, PEX may be less likely to rupture as a result of freezing."

The Key words are "less likely". They don't say it won't split if frozen. Water can do some amazing things when frozen or heated to steam.

Jim

[checkmate99]

As a retired plumber with 25 years in the business, I can tell you that Pex tubing can and does split when subjected to freezing conditions. It is less likely to split/burst then any other type of tubing/pipe when exposed to freezing, but it definitely will. So, winterizing your RV is a must if you live in the great white north!