Sleeving leaking copper pipe in slab with pex?

bk9

I've got a gas boiler two zone baseboard system using 3/4" copper piping. One of the pipes in the slab has a leak. This zone has other sections of pipe buried in slab, and it's all 60 years old, so I'm leery of doing a reroute in walls/ceiling for the leaking section and discovering a leak in another section shortly afterward. And the other sections would be more difficult to reroute overhead.

I've seen it suggested that 1/2" pex (oxygen barrier pex in this case since it's baseboard heating) can be shoved through the 3/4" copper pipe. I picked up a short piece of pex B to test (no short pieces of oxygen barrier pex available). I tried cutting the end of the pex to shape it like a spear, and used lube, and tried to shove it through a 3/4" copper 90* elbow fitting. No way will that fit through. But it will fit through if the bend is more gentle.

The pipe in slab comes up through the slab vertically at both ends. I don't know if 60 yrs ago when they installed this whether they used a bender to bend the pipe, in which case sleeving with 1/2" pex might work, or if they soldered on 90* elbows, in which case this will not work. Any ideas what common practice would be 60yrs ago?

Another sleeving option would be 3/8" pex. Assuming I could fit 3/8" oxygen barrier pex through this leaking copper pipe, would this cause issues with the boiler? I'm guessing that water in a baseboard loop is flowing slowly (and is ideally a perfectly closed loop with no leaks), so maybe the restriction and pressure increase before/decrease after the 3/8" pex isn't a big deal and won't harm the boiler?

If that would work with the boiler, then I guess it would just be a matter of using two adapters at each end to adapt from 3/8" pex to 3/4" copper?

EBEBRATT-Ed

The chances of getting 1/2" pex to slide through 3/4 copper for any distance is pretty low . Even if the 3/4 tubing has bends as soon as you hit one it will stop

GroundUp

Even if you were able to get the tubing in, heat transfer would not be great. Can you just locate the leak using thermal imaging and repair it? There will come a time when more leaks appear, this is going to keep happening. Maybe start considering a more "final" solution?

Solid_Fuel_Man

If I'm reading this correctly, this is a 3/4 copper run like under a doorway to feed baseboard on either side? 

I've seen that many times. Around here that was usually done with soft copper so you may get lucky....  but if there is something soldered, forget it. Time to either saw cut the floor, or reroute. 

JUGHNE

What type of room does this go under....entry....bedroom etc?

bk9

Solid_Fuel_Man said:

If I'm reading this correctly, this is a 3/4 copper run like under a doorway to feed baseboard on either side? 

I've seen that many times. Around here that was usually done with soft copper so you may get lucky....  but if there is something soldered, forget it. Time to either saw cut the floor, or reroute. 

Yes, for this particular zone, there are 3 sections between baseboards where the connecting pipe is in the slab, one of which is in the slab under garage, which is where the noticeable leak is.

For all I know, the other 2 sections have as yet undetected leaks. Won't know until I pressure test those sections separately (without the known leak).

Rerouting all 3 sections would be difficult, so it's kind of a last resort.

bk9

GroundUp said:

Even if you were able to get the tubing in, heat transfer would not be great. Can you just locate the leak using thermal imaging and repair it? There will come a time when more leaks appear, this is going to keep happening. Maybe start considering a more "final" solution?

I can see the wet spot on the surface of the slab (in attached garage), so yes, I could probably locate and repair it. But this is 60yr old pipe, so it probably wouldn't surprise anyone here that more leaks are likely.

bk9

Given that 1/2" pex probably wouldn't make it thru the 3/4" copper, is the idea of sleeving the buried 3/4" copper pipe with 3/8" oxygen barrier pex crazy?

Another sleeving option would be 3/8" pex. Assuming I could fit 3/8" oxygen barrier pex through this leaking copper pipe, would this cause issues with the boiler? I'm guessing that water in a baseboard loop is flowing slowly (and is ideally a perfectly closed loop with no leaks), so maybe the restriction and pressure increase before/decrease after the 3/8" pex isn't a big deal and won't harm the boiler?