Bending PEX with heat

[TDKPE]

I'm adding a pair of ball valves to the PEX plumbing in my little RV to bypass the Truma Combi water heater/space heater for winterizing.  Not supposed to put antifreeze in that unit, probably because it also provides hot air for heating the interior.

It's a really tight space where these valves will go, but I can get the crimper in there (one-handed style) to crimp the clamps.  But I'm severely limited in where I can actually put the valves unless I replumb the whole area, which I'm not about to do.  

It would help a bunch if I could put a little bit of permanent bend in the bypass tube I'm adding, so I don't have to use 90 degree fittings.  Is it possible to put a little bend in the tube with a heat gun, or will that compromise the tube?  I've never worked with PEX, so this is all new to me.  

At least it's a low pressure system.  

[Stwood_]

Take a small piece and do a bench test with a heat gun

[blackhat]

Pex has a strong inclination to return to the shape it was extruded.  Why not find a short piece of rubber fuel hose or similar that fits your pex fittings and use a couple regular hose clamps for that piece?

edit to add A heat gun is how you remove kinks in Pex.

[Stwood_]

Pex has a strong inclination to return to the shape it was extruded.  Why not find a short piece of rubber fuel hose or similar that fits your pex fittings and use a couple regular hose clamps for that piece?

edit to add A heat gun is how you remove kinks in Pex.

How about automotive heater hose...

[Robert Adams]

Is it pex A or pex B? Pex A uses pex rings. Pex B uses copper or stainless rings. B is much more common but A has advantages of larger fitting internal diameters. 

         Pex A you can heat to remove kinks in it. Pex B not quite the same. Pex A is overall more flexible but not quite as strong as Pex B (still way stronger than needed).

        You can use the plastic or metal bending 90s to hold a  bend but that's about it. Heat helps a little with Pex B in my experience but don't expect miracles.

[Roly]

I'm adding a pair of ball valves to the PEX plumbing in my little RV to bypass the Truma Combi water heater/space heater for winterizing.  Not supposed to put antifreeze in that unit, probably because it also provides hot air for heating the interior.

It's a really tight space where these valves will go, but I can get the crimper in there (one-handed style) to crimp the clamps.  But I'm severely limited in where I can actually put the valves unless I replumb the whole area, which I'm not about to do.  

It would help a bunch if I could put a little bit of permanent bend in the bypass tube I'm adding, so I don't have to use 90 degree fittings.  Is it possible to put a little bend in the tube with a heat gun, or will that compromise the tube?  I've never worked with PEX, so this is all new to me.  

At least it's a low pressure system.  

 Tom I was able to put a 2" R  90° bend in 1/2" pex  B with minor flatting of the tube using a conduit bending blanket.  You have hold it in the position you want until it is cold.   That would be the max bend you could make.  I have no idea if it compromised the tube or not as far as long term or how it reacts to a freeze thaw cycle which is probably the quality you want.   Roly

[TDKPE]

Thanks, guys.  It's PEX-b according to the label.  I have the stainless crimp clamps, with the little squeeze bump for crimping, and a one-handed crimp tool, since it's pretty snug where I have to do this.  I also bought a bag of 90's, as I think I have to use one due to the way one of the two valves will have to be oriented.  But the PEX line may (probably will) have to bend around a sink waste line, which is why I was asking about bending the stuff, and I don't want to stress the existing plumbing it will be tapped into.

I'll post before and after pics when I get there.  I wimped out yesterday after doing yard work all day.  I'm feeling my age, unfortunately.  
 

HD had a 5 ft stick of 1/2" white PEX; white so it's obvious when I need to find it on the road, in the dark, with all the other lines being red and blue.  

[attachment=27360]

[barnowl]

Can't you cut the bypass halves further away from the heater so as not to be so cramped for space?

[TDKPE]

Can't you cut the bypass halves further away from the heater so as not to be so cramped for space?

Unfortunately, no.  While the tubes are maybe a foot long, there's a drain pipe right in the middle of where the bypass tube has to go.  So I need to cheat it toward the heater, which is more open than cheating it the other way.  

The blue in front is the cold water supply, which turns 90 degrees to the right to the inlet, possibly using a SharkBite fitting.  It may be possible to put the first valve there, but I'd need to add another 90 and I think it's easier to put it in the horizontal part on the floor and just tilt it back few degrees.  It's also oriented correctly with the handle on top and the common to the left where the incoming water is.  

The red hot in the back is tucked into a bit of a recess in the heater where it goes vertical, so the valve has to go on the horizontal run in the back corner between the floor and the van wall.  Since these valves aren't available in left/right handed versions, the one that'll go in the red line has to lay on its side with the stem pointed up.  That's where the 90 fitting will go, to send it across and past the drain line.  I'll decide if I need to add another 90 for the cold side, but I'm hoping to just land it on the stem of the other valve.


[attachment=27361]

It looks like there's a lot of space in there, but I shot that through the opening for a drawer.  There isn't a lot of space in there.  I removed the coaxial combustion intake/exhaust for the heater (silver round thing at lower-right), and a hot air vent that curled back out of the shot.  With all that stuff back in place, I have to feel around for the heater drain valve, which is at the end of the blue line just out of the shot at the bottom-left (if drains through a tube through the floor when opened).  I'll probably have to feel around for these two bypass valves when I winterize, but that's not a problem as long as I can see roughly where they are.

Oh, and all that junk on the floor is from the coach builder, who never cleaned up the areas that folks don't see when buying. I have to get my mini wet/dry vac in there to clean it out.

[barnowl]

... Since these valves aren't available in left/right handed versions, the one that'll go in the red line has to lay on its side with the stem pointed up.  ...

Just mount one of the valves "backwards"? And maybe re-route the drain line to a different place, and patch the existing hole?