PEX fittings vs. Gray RV tubing

[tmsnyder]

Winterizing the RV today. In the past this was a major PITA b/c the hot water heater has no bypass valves.   My local RV store has a kit which add this, but requires unthreading the brass inlet fittings from the aluminum hot water tank bungs.   Mine would not budge, and I didn't want to risk ripping the bungs off of the tank. 


The grey 1990 tubing measured 0.625 OD and the nearest fitting I could get on with the calipers measured 0.500"  To me, that seemed like the same diameters as PEX, so I bought 3 1/2" valves and two T's, and a stick of 1/2" PEX.   Cutting into the tubing entering and exiting the hot water tank, I valved both lines, then T'd the lines and installed a valve connecting the inlet and outlets. 


To my horror, I found that the ID of the gray tubing is bigger than the PEX.  It was a sloppy fit, but once crimped onto the valve or T the connection was watertight!  PHEW!  Pressurized with air to 50psi and checked with soapy water showed no leaks. 


I'm now able to blow out the lines, flush with 1 gallon of antifreeze, then blown clear again easily.   Also drained the hot water tank and blew those lines into the emtpy open tank.   Turned a real PITA job into an easy 20 minute job.   


Long story short, the old grey stuff is close enough to work with 1/2" PEX just fine.  (I did use the copper crush ring style of crimper, not the little ear crimper style)

[RickNC]

For future reference Home depot has the proper conversion kit for Gray polybutyl to PEX.


https://www.homedepot.com/p/1-2-in-Brass-PEX-Barb-Polybutylene-Coupling-UC4008LFA/202270576

[CapnDirk]

Why did you need to put a bypass valve in to drain the hot water heater?

[tmsnyder]

Not needed to drain the water heater, but very helpful when flushing out the lines.   Takes that big volume of the water heater out of the picture.


This way I can flush the water lines from the pump or city water connection with RV antifreeze without having to fill the water heater.  8 gallons of the stuff gets expensive.  Bypassing the heater gets it done with just one gallon.

[tmsnyder]

Good to know, I would have made the trip to HD if I knew those existed, but it actually turned out to be not necessary. There was enough crush with the crimper and the solid copper rings to make the seal.  Might be needed with the other style of crimper though, the one that grabs a little ear on the band.

For future reference Home depot has the proper conversion kit for Gray polybutyl to PEX.


https://www.homedepot.com/p/1-2-in-Brass-PEX-Barb-Polybutylene-Coupling-UC4008LFA/202270576

[Rickf1985]

Polybutyl has a bad habit of breaking down. It was outlawed in mobile homes years ago due to so many lawsuits. For some odd reason they continued to use it in RV's with the same results, constant leaks. It is not so much the tubing but the connections that leak.

[TerryH]

It is not so much the tubing but the connections that leak.

X2

[CapnDirk]

Not needed to drain the water heater, but very helpful when flushing out the lines.   Takes that big volume of the water heater out of the picture.


This way I can flush the water lines from the pump or city water connection with RV antifreeze without having to fill the water heater.  8 gallons of the stuff gets expensive.  Bypassing the heater gets it done with just one gallon.

Makes sense now, maybe have to do it to mine.  Cheers.

[tmsnyder]

X2

I can believe it , the grey tubing fittings are able to spin around at the connections.  They almost seem loose.  The polybutyl crimped onto the brass PEX fitting, even though it started out loose on the fitting, ended up a much tighter seal then the old polybutyl seals.


I'm not going to be pulling all the old grey stuff out to replace it with PEX though, not anytime soon at least.