Hot water leak under slab

[Ronzo]

I recently went through a repair and restoration process for a hot water leak under the slab of my home. It seems that the hot lines tend to develop leaks more often than the cold lines. Since then I have been trying to find out some info about this. I am using a small recirculating pump on my water heater that gives me much quicker hot water to my faucets. It's an extremely small pump that really works great. However, in talking to several plumbers, I have been told of two possible theories that would affect the pipes developing a leak. One is that the pipes (copper) might tend to corrode faster by being warm/hot all the time by accelerating the chemical reaction of corroding. The second is that without the recirculator, the pipes will expand and contract more frequently depending on temp change, causing stress . Any opinions would be appreciated. Thanks.

 

[hj]

If the pump is oversized, it will circulate the water to fast and cause erosion, so you need a valve on the DISCHARGE side of the pump to restrict the flow. The hot/cool expansion and contraction will cause wear if the pipe was installed with any rocks, stones, or debris touching it. Also if the installers "kinked" the tube where they bent it up into the walls, heating/cooling will flex it like you were bending it back and forth and cause a crack. Keeping the water at a fairly constant temperature will limit these problems.

 

[Sponsor]

 

[Jadnashua]

If joints are not prepped properly, and the water is pumped too fast, the slight lip caused by a tubing cutter if not straightened, can cause turbulence, and eventually, eat holes in the pipe by cavitation. A properly setup recirculation system doesn't move water very fast.

 

[Ronzo]

Thank you for your replies. The pump I am using is a 1/25 horsepower pump made by Grundfos. These pumps are very low output and designed specifically for recirculating hot water in a residential setting. The decision I am contemplating is whether I'm better off keeping the piping constant temp with the pump or going without the pump and letting the pipe heat and cool every time I use hot water in the house???

 

[Jadnashua]

Personally, I'd let it run. The one I have has been in place now for about 12-years...no issues (yet).

 

[Bgard]

Do you have a water softener? If so what is the hardness of the water? Is the copper pipe imbedded in the concrete where it may be contacting steel rebar or wire mesh?

 

[Ronzo]

No water softener or RO. House is 23 years old. Recirculator installed about 4 years ago. Water is not naturally soft, but tastes fine and no corrosion around fixtures, etc. I have no way of knowing the exact condition of the pipe to the concrete or mesh. In Las Vegas they put the plumbing in the ground work and then poured the slab on top. Not supposed to let copper contact steel, but no way of knowing if it does. It could be electrolysis if that is the case?? Right now my only decision is whether to let the recirculator run or disable it. Either way, I'm expecting more leaks sometime in the future. I just don't want to do anything that would accelerate the inevitable. Thanks for your concern and reply.