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GeeJay 03-01-2011 01:27 AM

PEX Brass Fittings Turning Inside Tubing After Cinch Clamped
First off, PLEASE, I don't need debate on which PEX connection system is best, I have read enough of that to decide all systems, properly installed, will work well and users all seem to tout the system they use.

I have just started re-plumbing my RV to bring the fixtures and connections up to quality residential standards and to fit stop valves and SS flex connections where there are none.

Most of the OE main waterlines are PEX with plastic PEX fittings, which are the standard in many RVs, and Otiker type SS cinch clamps. However, the manufacturer uses clear vinyl reinforced (braided) tubing (hose) for faucet connection lines, something out of circa 1960 RV plumbing technology, using the same cinch clamps to connect to PEX tees.

I had a leak last summer at the tee for the kitchen hot water connection , which is only a couple of feet from the water heater, because the vinyl hose had swollen so much that it lost the seal on the plastic PEX tee. I removed the SS cinch clamp and fitted a SS hose clamp, which I could tighten more. But that only lasted a few weeks before that also leaked and I felt I couldn't tighten the clamp further without deforming the plastic PEX fitting.

As I already had major plumbing renovations in mind, I then removed that section of the PEX line and replaced the tee with a brass one and ran PEX from the tee to a new stop valve and a SS flex connection line to the faucet.

That worked out well and made me decide to stick with that for the renovations. Also, I have had no problems with any of the OE joints and they are numerous, as their policy seemed to have a "if it's too short - don't replace it -just add another bit". I decided to use all brass PEX fittings rather the plastic type common in RVs.

I removed the OE PEX lines to be replaced and after pre-fabricating one replacement section and before installing it, I found to my dismay that the tubing would turn on the brass PEX fittings. I then tried turning one of the OE sections that I had removed and found the PEX would not turn on the plastic elbows and tees but would on the brass stop valve use as a low point water drain valve. I suppose the plastic fittings deform slightly when crimped, making it impossible to turn on them.

Before I panicked I decided to test this new section, so I fitted the 3 OE stop valves I had removed to the open end fittings and hooked it to the 70 PSI RV park water supply, and to my relief all the joints were leak free. I have my outside water supply connection regulated to 60 PSI and my water pump for the fresh water tank set at 50 PSI, so this would seem to indicate I should not have leak problems ether when connected to an outside water supply or when operating self contained from our water tank.

On the plus side, the ability to turn the PEX on the fitting does make it easier fitting a prefabricated section in the tight spaces in the RV.

So... my query is, is it usual for these type of connections to turn on the fitting without losing the seal?



Daniel Holzman 03-01-2011 07:06 AM

I have Wirsbo PEX and fittings in my house, both plastic and brass fittings. I have had the same experience, the plastic fittings do not movcannot rotate, sometimes the brass ones do. Neither of them leak.

However, you may want to read about the series of lawsuits against manufacturers of brass PEX fittings, including Zurn and recently, so I understand, Wirsbo. Seems the issue is corrosion of the brass in the case of acidic water. I have decided to use plastic fittings when possible, brass only when absolutely necessary, due to the fact that my water is quite acidic, and I do not want to replace fittings again.

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