Long underground water line freeze protection

[JpNH]

Hoping to get some feedback on the best strategy for my unique setup.

Setup: I built an office for my wife in our barn, and ran a water line from our house to supply the barn (for the bathroom). It's a 250ft run, in 1" black poly pipe, in a 4" PVC conduit. It is buried below the frost line except at the ends where the foundations prevented going more than 2-3 feet which leads to:

The problem: we just had a week of sub zero temps. My heat cable that ran the whole length of the conduit shorted out, and I had a freeze-up. That's resolved now (thank goodness for plastic piping) but I'm wondering if heat cable is the best option.

My thought: I can't seem to find heat cable longer than 150' that doesn't require a separate controller. The failed one had a separate controller, but upon failure I realized it's only rated for 75' (chance the failure,likely), and I'd rather not run 2 shorter cables (one from each end)...

So please let me know if I'm over complicating this... But I'm thinking about running a closed loop with two 1/2" radiant heat pex lines through the conduit (next to the supply line) with a temp controlled circulation pump from the office's water heater (return line back to the water heater supply line). Would this be a more effective/reliable option, or should I just shut up and run more heat cable?

Please advise,
Thanks

 

[Twowaxhack]

I’d run a heat cable from each end and only use enough to keep the shallow ends from freezing.

A 500’ loop is a long way

 

[JpNH]

I’d run a heat cable from each end and only use enough to keep the shallow ends from freezing.

A 500’ loop is a long way

That's what I now currently have, a 30' cable from each side. Just wondering for long term

 

[Twowaxhack]

That's what I now currently have, a 30' cable from each side. Just wondering for long term

The best solution would be to bury the pipe deeper.

Next best solution is to drain the pipe when it gets cold.

Next best solution from that is heat tape.

I’d pack a moving truck and move to Florida. That’s the best long term solution.

But if you want a 500’ hot loop and want that expense, it’s doable.

 

[JpNH]

The best solution would be to bury the pipe deeper.

Next best solution is to drain the pipe when it gets cold.

Next best solution from that is heat tape.

I’d pack a moving truck and move to Florida. ✌ That’s the best long term solution.

But if you want a 500’ hot loop and want that expense, it’s doable.

1st and 2nd, and 4th solutions aren't possible, so #3 it is

 

[Mitchell-DIY-Guy]

You are NOT trying to heat the line just keep it from freezing.
Your idea of basically a radiant heat line in your conduit is a sound one. Things like this are done in northern climate car washes all the time.
In a renovation of the car wash I owned, we did exactly that in the “trough” that held all the water and chemical lines that fed each of the five bays. The trough was about 12” x 12” x 120’. We ran heavy duty radiator hose (not PEX) in a loop through the insulated trough; it was probably about 260’ total. The heat source was our primary hot water system. But to do it right we used glycol, not the hot water, in that heated loop. We had a stainless steel plate heat exchanger, a small circulation pump, a small expansion tank, some fittings and valves for filling, draining and control and a thermostat on the pump with a sensor in the attic. If the attic dropped to 35, the system was activated. We didn’t need a second pump for the hot water since we tapped into a line on the hot water system where the water was moving.
That was at a car wash; you couldn’t have a glycol loop and plate heat exchanger on a potable water system.
But your thought is a sound one.

 

[JpNH]

You are NOT trying to heat the line just keep it from freezing.
Your idea of basically a radiant heat line in your conduit is a sound one. Things like this are done in northern climate car washes all the time.
In a renovation of the car wash I owned, we did exactly that in the “trough” that held all the water and chemical lines that fed each of the five bays. The trough was about 12” x 12” x 120’. We ran heavy duty radiator hose (not PEX) in a loop through the insulated trough; it was probably about 260’ total. The heat source was our primary hot water system. But to do it right we used glycol, not the hot water, in that heated loop. We had a stainless steel plate heat exchanger, a small circulation pump, a small expansion tank, some fittings and valves for filling, draining and control and a thermostat on the pump with a sensor in the attic. If the attic dropped to 35, the system was activated. We didn’t need a second pump for the hot water since we tapped into a line on the hot water system where the water was moving.
That was at a car wash; you couldn’t have a glycol loop and plate heat exchanger on a potable water system.
But your thought is a sound one.

Thanks, I knew there had to be some sort of proven application of this lol! Probably going to stick with the heat cable for now (since they're already purchased), but maybe if they have issues again I'll make the switch.

 

[JpNH]

Follow up question for everyone: I installed a 2nd pressure tank in the barn with the intention of not overworking my house well pump. I also put in a booster pump since I was losing considerable pressure sure to the long run. Since the barn water use is pretty low the pressure tank gets at least a day's worth for flushing/hand washing before the pump kicks up, but could this be contributing to the issue since the water is not frequently moving in the supply line? Should I just eliminate the 2nd tank to keep water moving more regularly? Or maybe run a return line back through with a circulator that runs at a regular internal to keep it from sitting still in cold weather? Any thoughts would be greatly appreciated!

 

[Mitchell-DIY-Guy]

Thanks, I knew there had to be some sort of proven application of this lol! Probably going to stick with the heat cable for now (since they're already purchased), but maybe if they have issues again I'll make the switch.

Just a couple of things to consider: first, any kind of heat trace tape MUST BE IN CONTACT with the item its trying to prevent from freezing. So, if you are using this on a water pipe to prevent freezing, you need to have it firmly adhered to the pipe or tube, and then insulated. Follow the instructions very carefully as provided by the manufacturer.

Second, the "hot water" system I used for heating my trough in the car wash was very reliable; never had any issues. Installed once, and forgot about it.

On the other hand, my touch-less automatic car wash had heat trace tapes on the arms to keep them from freezing, as well as on certain other components. The arms were essentially formed 1" x 1" stainless steel tubing, with about 8 bosses welded into them and the high pressure nozzles threaded in. The heat trace tape ran down each arm, and the entire thing was covered with 1" think foam insulation. The electrical connections were made at the top. It was almost a regular occurrence that the heat trace tapes would short out, and cause the arms to freeze. Happened several times in my 6 years of ownership. The wiring was just not robust enough to survive a Michigan winter at a car wash, with thousands of gallons of chemical laden water was blowing around in sub-freezing temperatures.

Surely your conditions will NOT be like a car wash...but just mentioning this to you.

 

[MicEd69]

If the conduit is below the frost line for your area, the best solution is what Twowaxhack said in the first response to this post; “run a heat cable from each end and only use enough to keep the shallow ends from freezing.” That should only be a few feet, not the total 250-foot run. And as Mitchell-DIY-Guy said, the heat tape does need to be in contact with the pipe and insulated for it to work properly. On Black Poly pipe, you also need to be careful with the wattage per foot of the heat tape; 12 wats per foot maximum I believe. My assumption is that both ends of the conduit where the water line enters it are in a controlled environment, and that they are insulated at least down to below the frost line. A heat tape from each end will resolve your problem with the least amount of work.

But if you would like a more exotic systems, instead of installing a recirculating loop of hot water which will increase your water heating bill substantially, you could consider running just a second water line and make a loop between your house and the barn. That second line could be 1/2 inch, not the full 1 inch of you supply line. Then just keep the water in those lines circulating. As you are on well water, I’m not sure what level of water treatment you have in place. But even if you were on municipal water, you would not want the water to recirculate for days without being used. So, you would want to have a control system to continuously purge water from this loop to keep that loop “fresh”. Control wise, this would not be any more complicated than the hot water circulating system, and would be less piping, and much less operating cost.

Being an engineer, the second system is an attractive approach. But being a more practical engineer, buy two short and appropriately watts/foot heat tapes and put them on shallow parts on the pipes on each end of your run. Insulate them and close off the ends of the conduit and you should be good.

 

[fixitron]

I would use a 20-30 ft. heat cable (not heat tape) that is inserted into the black poly water pipe at a threaded Tee on both the house end and barn end. You don't have to keep it turned on, but if you do you they are self regulating and don't need any separate controller. When the water line freezes, then turn on the heat cables and it will thaw quickly. You could also dig down and lay sheets of 2" XPS (blue or pink board) centered on the pipe (preferably 3 or 4 ft. wide sheets), which will use the heat of the earth to keep the line from freezing.

 

[Jeff Handy]

Just another goofy idea.
How about a small blower to push ambient temp air from the house, all the way through that 4 inch conduit?
Might take the edge off enough to keep from freezing.
Also, the old trick of keeping a faucet in the office on a slow trickle during cold snaps.

 

[JpNH]

I would use a 20-30 ft. heat cable (not heat tape) that is inserted into the black poly water pipe at a threaded Tee on both the house end and barn end. You don't have to keep it turned on, but if you do you they are self regulating and don't need any separate controller. When the water line freezes, then turn on the heat cables and it will thaw quickly. You could also dig down and lay sheets of 2" XPS (blue or pink board) centered on the pipe (preferably 3 or 4 ft. wide sheets), which will use the heat of the earth to keep the line from freezing.

Interesting about running it inside the waterline, does it have to be a specific type of heat cable that can be submerged?

 

[JpNH]

Just another goofy idea.
How about a small blower to push ambient temp air from the house, all the way through that 4 inch conduit?
Might take the edge off enough to keep from freezing.
Also, the old trick of keeping a faucet in the office on a slow trickle during cold snaps.

I've been toying with this fan idea also...

 

[Jeff Handy]

Blower fan in the house, suction fan in the barn.
Probably less watts than heating tape also.

 

[JohnRK]

Hoping to get some feedback on the best strategy for my unique setup.

Setup: I built an office for my wife in our barn, and ran a water line from our house to supply the barn (for the bathroom). It's a 250ft run, in 1" black poly pipe, in a 4" PVC conduit. It is buried below the frost line except at the ends where the foundations prevented going more than 2-3 feet which leads to:

The problem: we just had a week of sub zero temps. My heat cable that ran the whole length of the conduit shorted out, and I had a freeze-up. That's resolved now (thank goodness for plastic piping) but I'm wondering if heat cable is the best option.

My thought: I can't seem to find heat cable longer than 150' that doesn't require a separate controller. The failed one had a separate controller, but upon failure I realized it's only rated for 75' (chance the failure,likely), and I'd rather not run 2 shorter cables (one from each end)...

So please let me know if I'm over complicating this... But I'm thinking about running a closed loop with two 1/2" radiant heat pex lines through the conduit (next to the supply line) with a temp controlled circulation pump from the office's water heater (return line back to the water heater supply line). Would this be a more effective/reliable option, or should I just shut up and run more heat cable?

Please advise,
Thanks

 

[JohnRK]

1st off ALL Piping is to be below the frost level. If this is not possible then you can heat trace the Piping which is above the frost level and all other piping that is not protected from freezing temperatures. You DO NOT have to heat trace the entire run