Unsolvable Problem? Frozen pipes at end of line behind shower above unheated garage

[Eric Wininger]

I have a 2nd floor bathroom above an unheated garage. There is insulation but no heat in garage. This winter these pipes froze three times and on the final freeze both the hot and cold lines burst. It froze towards the end of the line, behind the shower. The line runs from the unfinished basement up the wall (between garage and heated mud room) to a 2nd floor vanity, toilet and then shower in that order.

For those that ask why not keep the water running I will answer that I tired that and the drain froze and flooded the bathroom. In addition, the Moen faucet on the shower at the end of the line is designed to only allow cold to drip. For hot you need it on full blast.

I brought in a professional plumber. He wants to reroute the hot and cold lines into the ceiling above the adjacent heated room (below heated bedroom above heated library room) so only the last foot of the pipe is above the garage (rather than the whole line). He will add insulation. Will this work?

The idea of heat tape was brought up but I believe it is a fire hazard to put heat tape on pipes behind sheetrock?

I asked about installing a Watts Recirculating pump but he said this won't work. His explanation was cryptic but he said "because hot freezes faster than cold" it won't work. He said the line will still freeze. He said because the shower is last on the line it would require me to leave the faucet running. It would also require me to find a new faucet that allows hot and cold to drip, if this exists for a shower.

He further agreed to install a third return line and a recirculation pump to further prevent freezing. I assume this will only protect the hot and return, but not the cold line?

Price for this is $2200.

Comments?

 

[Jadnashua]

Insulation only slows down heat loss, and in certain instances, could make your pipes freeze faster by blocking their access to any heat in the area! You'd want no insulation between the pipes and the heated room, and as much as possible between the pipes and the unheated areas so that some room heat can get to them as easily as possible.

Since you need to warm both the hot and the cold lines, you may want to use a retrofit recirculation system that uses the cold line as the return. Otherwise, the cold line would just stay stagnant and freeze. Most of these work by having a temperature controlled cross-over at the point of use...only opening when the temperature of the hot line is below some value (often around 105-degrees). THen, that valve opens and flows water back in the cold line until the hot line reaches the cutoff point, and then the valve closes. It would depend on how far apart the shower and the vanity lines were whether you'd need one or two of those crossover valves. This has a much better chance of preventing freezing lines. But, if you have a power failure, all bets are off (same if the pump or cross-over fails).

When you have a dedicated return line, it would do nothing to the cold line itself.

The reason that once-heated water can freeze faster than one not run through the WH is that heating it forces out any trapped air and can end up making it purer by having some of the minerals removed. But, that assumes both the hot and cold were allowed to get to the freezing point from no flow...then, once they both were cold, the one that had been heated normally freezes faster (impurities often lower the freezing point).

 

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[Eric Wininger]

Forgetting about the cost, am I better off with A or B or C?

A) Rerouting pipes (between two heated rooms) and adding a third return line along with a recirculating pump? Presumably I would still have to keep the cold only dripping on cold nights? (The last one foot of the pipe would be above the unheated garage)
B) Rerouting pipes (between two heated rooms) and NOT adding a third line but adding a recirculating pump. (I guess I'm totally screwed if the pump fails since I can't drip hot and cold on the shower at the end of the line at the same time)
C) Don't reroute and just add a recirculating pump and turn it on when it is cold.

 

[Terry]

"I brought in a professional plumber. He wants to reroute the hot and cold lines into the ceiling above the adjacent heated room (below heated bedroom above heated library room) so only the last foot of the pipe is above the garage (rather than the whole line). He will add insulation. Will this work?"

This sounds good. The pipes should be in warmed areas, with the pipes within the insulated shell.
Warm inside, then pipes, then insulaton, then cold. You want to trap warm with insulation of the far side of the pipes like a blanket.
The warm interior should keep that section from freezing.

Then you need to worry about the last bit. Is there a reason the bathroom has no heat?

 

[Eric Wininger]

"Then you need to worry about the last bit. Is there a reason the bathroom has no heat?"

Bathroom has heat. But it is above an unheated garage. So the last foot of the pipe will be above the unheated garage but between the heated bedroom and heated bathroom.

"This sounds good. The pipes should be in warmed areas, with the pipes within the insulated shell."

Should I bother with the third return line? Recirculating pump? Get both? Get neither?

 

[Terry]

"Bathroom has heat. But it is above an unheated garage. So the last foot of the pipe will be above the unheated garage but between the heated bedroom and heated bathroom."

In that case, I would be pulling insulation out and moving it to the cold side of whereever the pipe is.

 

[Jadnashua]

As I said, a third (dedicated) return line will do NOTHING for your cold water pipe. Having the pipe on the warm side of the insulation should be all you need, but if you also want hot water faster, I'd consider using the cold line as the return rather than a new line. With mine, I find that flushing the toilet purges the warm water from that line, and cold then runs cold.

 

[Eric Wininger]

As I said, a third (dedicated) return line will do NOTHING for your cold water pipe. Having the pipe on the warm side of the insulation should be all you need, but if you also want hot water faster, I'd consider using the cold line as the return rather than a new line. With mine, I find that flushing the toilet purges the warm water from that line, and cold then runs cold.

Plumber started work today and he was thinking of the possibility of adding heat tape over the last foot of the plumbing line, which is above the unheated garage (the rest of the line will be moved to ceiling of heated library which is below heated bedroom).

Is heat tape behind a wall a fire hazard? If we add an access door does that make it safer?

Will one foot of line freeze if it is properly insulated?

 

[Jadnashua]

Insulation only slows heat loss. IF there is an air leak, no amount of insulation (assuming fiberglass which acts like a great air filter when moving air is there) will prevent things from freezing. But, moving the pipe to the room side of the insulation is usually enough IF you don't' have air leaks.

 

[Eric Wininger]

Insulation only slows heat loss. IF there is an air leak, no amount of insulation (assuming fiberglass which acts like a great air filter when moving air is there) will prevent things from freezing. But, moving the pipe to the room side of the insulation is usually enough IF you don't' have air leaks.

I am having quite an unsolvable problem here. I am rerouting my pipes to a heated room but it still has to terminate above unheated garage behind shower. Apparently:

1) Insulation only slows heat loss so this won't work
2) I was told today installing Watt's Sensor Valve Kit (for recirculating pump) behind drywall behind shower is a code violation (see picture)
3) Installing heat tape behind drywall behind shower is code violation

What is the solution? Best we can come up with is installing a third line with a recirculating pump. Cold will remain unprotected. Any better answers?

 

[Jadnashua]

If you keep the pipe on the room side of the insulation AND keep the room heated AND you don't have lots of air leaks, the pipe won't freeze in the wall. Enough heat from the heated room will go through the wall to the pipe. But, as I've said, if the walls aren't sealed well, and you're using fiberglass insulation, the fiberglass won't stop the breeze. Normally, with no breezes blowing in the wall, the temperature gradient means the room side is just that, room-temp, and the far side of the insulation is the outside ambient, and it is fairly gradual change from one side to the other.

To be code compliant, you may be able to get there with an access panel. If that's possible, you might be able to use a valve there and a recirculation system that uses the cold line for the return line...then, both the hot and cold should stay above freezing. I'm by no means fully up to speed on all of the code issues, but I think the problem is access, and a panel would solve that.

 

[Reach4]

I am having quite an unsolvable problem here. I am rerouting my pipes to a heated room but it still has to terminate above unheated garage behind shower.

I would say that the pipes to the shower terminate at the shower. So I think you are saying that the pipes will pass through an unheated space. I think Terry described the solution in reply #6 -- put the insulation between the pipes and the unheated space and not between the pipes and the heated space. Does that work for you?

I have heard that PEX survives freezing better than other types, but that you should not plan to have it freeze.

I thought your idea of bundling your pipes with insulation and having a hot water recirculation pump and line in the bundle was good thinking. I am not a pro. Terry is.

 

[Jadziedzic]

How about making the area where the pipes run behind the shower part of the heated portion of the room? If you can route a 2x10" rectangular duct into that area from the ceiling of the heated room in front of the shower (with a rectangular grille in the ceiling) and provide a return path back into the room (another rectangular duct along the joist cavity below the floor - which hopefully runs the "correct" direction into the room and is terminated by another rectangular grille in the floor) convection currents would keep the area relatively close to room temperature. You might even get by without a return path. Enclose and insulate the heck out of the portion behind the shower where the pipes are located, and likewise for the joist space in the ceiling above the "supply" duct.