Water service freezing

Zman

I am working on a single family residence that has a 4" ductile service line (yes that is four inch) which is about 270 feet long. The middle section of the pipe was installed at a depth of about 6' (9' is minimum in this area) due to a rock ledge which was encountered. I believe the line is insulated with 4" blue board and shares a trench, and insulation with the sewer line.

The main froze this winter due to a lower than usual snow pack and the house being occupied part time.The blockage was about 80 feet long. I don't believe it has frozen in the past 17 years with the original owner.



I am looking for solutions. The obvious first choice would be to dig up the pipe (under the driveway) and reinsulate with spray foam, possible instal heat trace.



Other thoughts would be an "internal" solution. Has anyone used an internal heat trace or recirc tube. The access to the end of the main is quite good. It is part of a municipal system. I am sure there will be concerns about potential contamination that will need to be addressed.

Thank you in advance,

Carl

Jamie Hall

I'm glad I don't live

in Alaska!  Which is, I assume, where you are...



If you have standing water in a pipe, and the pipe is above the depth to which the ground freezes, the pipe will freeze.  Insulation -- unless it is wide enough to extend the path for the heat (or cold, as you prefer) to the required depth, isn't going to help (for example, in your case, with the pipe and six feet and the required depth nine feet, you would need to extend the insulation above to pipe to a distance of three feet on either side).  Insulation all around the pipe won't help either, if there is no flow (if there is flow, insulation will help by reducing the flow required to avoid freezing).



Nor will recirculation within that one pipe -- say from the service tap to the house and back -- unless you have enough flow in the pipe so that the friction heat loss is enough to keep the pipe from freezing (you'd need a lot of flow even in a small pipe to do that, never mind 4 inch).



So... I expect your best bet will be a heat trace (which, incidentally, will also keep the sewer from freezing, in the event there is a small flow or standing water in it).  If you were to put the water main, the sewer line, and the heat trace all within an insulated enclosure, you could probably get away with relatively little heat (I'd have to run the numbers to quantify "relatively little").  The idea of threading it through the existing water line is rather attractive -- say a hot water pipe within the other pipe, sort of a coaxial arrangement -- but you would have some interesting fittings at both ends...

SWEI

trenchless replacement

would be my first choice.  Do you have anyone there with the equipment?  If the line thaws, you might even be able to pull a replacement without bursting.  Surely something smaller (possibly a 1-1/4") would serve the needs of a residence?



You could pull either an electric heat trace or a pair of hot water heating lines at the same time.

Zman

Trenchless

I am actually in Colorado at about 9500'

The water system has no tank for this neighborhood. It is  constantly pressurized by a pump station at the bottom of the hill ( I am working on getting a tour). The house has a fire suppression system with a 1 1/2" line and a domestic/irrigation 1". I think the main is oversized. I am not sure by how much. I believe the static pressure is about 55#.

Swei, I like the direction you are going. Do you have more information?

Thanks,

Carl

icesailor

Kind of an unusual situation.

I look at this problem differently but there are "considerations".

You could install heat traces but you need to dig it up to install the wires. I understand that the problem is in an area where there is a ledge issue so you can't get the pipe deep enough. Where the ledge isn't a problem, and it is deep, the ground is well above 32 degrees. If you have a good snow pack, or this is not a shaded area, it won't freeze. If the house is near the problem area, run a poly line from the house to the far side of the bad area and connect it to the main with a Corporation Cock, connect it with a pump and circulate the water when the water temperature goes below a set point. The flowing water will provide enough BTU's or warmer cold water that the freezing will not occur. You can also rig a electric solenoid as a "Dump Valve if the water gets too close to 32 degrees. The warmer water from the water system will keep the water flowing and stop freezing. When you run the water in the house, if the water hurts your hand, it's going to freeze. Ice water in a lakes is 32 degrees and COLD. 

It won't matter how much you try to put insulation around the mess. Insulation only slows down the rate of heat gain or loss. I've had freeze-ups where you had to rip the insulation off to thaw the pipes. The pipes froze when the cold worked through the insulation and got to the insulated pipes.

Zman

Digging

I think the problem can be solved by digging it up, insulating and adding heat trace. With at least 80' of effected pipe it would be intrusive to say the least.

I am really intrigued by some of the trenchless solutions out there. Especially ones that water districts have approved.

Thank you all,

Carl

SWEI

thought it was already insulated?

If the replacement bundle is smaller than the ID of the 4", you should be able to winch them in without having to burst the old pipe.  A 2" along with either a pair of 1/2" snowmelt pipes or some heat trace tape should be easy (barring inconvenient elbows.)  2" PEX with a heat trace and some insulation might be another option. 

Steve Whitbeck

redundency

If you run heat tape I would run at least one spare for when the first one burns out.

Hate to dig it up again.

Zman

Agreed

Thanks Steve,

If we dig, I was thinking (2) heat trace runs and 12" of closed cell spray foam. The dig solution is looking ridiculously expensive.

How crazy would it be to cap a 200' piece of pex and put heat trace in it. This could then be slid inside the 4" ductile from the house. I have never heard of this being done, what would be the drawbacks?

Thanks All,

Carl

SWEI

cap a piece of 2" PEX?

Not quite sure what you are describing (thanks.)

Zman

Inside

I was exploring the idea of suspending a piece if 3/4" or 1"  inside the 4 " ductile. The heat trace would be inside the pex and dry.

I am not sure if pex is exactly the same on the inside and out. Would the chlorine damage the outside of the pex?

Soft copper would be another thought, would it have an adverse reaction to the ductile?

Carl

icesailor

Freezing Water Services:

FWIW,

If it is 4" Ductile Iron, and it is straight run pipe with gaskets, and there aren't any 90 degree turns between the inside if the house and the area where the service is freezing, and there is a "Tee" fitting that you can get into, push a length of 3/4" 200# PE pipe into the inside of the 4" DI pipe. Use a double tapped bushing, push the 3/4" pipe past the shallow area, connect the house end to a bronze circulator and circulate the water through the effected area. Like a closed loop ground water heat pump. The warmer water in the deeper area will provide enough heat to stop the freezing. If the affected area is under a driveway that is shaded for part of the day, it will get frost. You can spend a lot of money on energy to try to heat the water but if you circulate warmer water that is available in the service, you will solve the problem.

An easier low tech solution is to bleed off potable water from the service during times of cold frost times. If the service is Ductile Iron, it is metal the whole way. It can be thawed with an arc welder if the metal goes into the building. Connect a ground lead to the inside from the welder and have a connected point on the DI service. The electrical current will do the rest.

You can bury 24" of solid foam insulation around the pipe. Unless you find a heat source to overcome the cold source, the service will freeze.. Why not use the warmer soil in the deeper area as a heat source? Its free.

But you guys seem to see this problem from a far more complicated solution than I do. Keep It Simple but don't be Stupid, KISS.

Here's an example of what you are dealing with.

A customer called with no water in September a year or so back. The building was condo'ed shops from an old auto repair facility, done on the cheap. No plans for anything. HVAC was gas heat and AC through furnaces. The compressors were in three locations. Between the buildings was a pit with the water services. Everything seemed to go under the buildings with an unaccessable crawl space. The gas piping had leaked and it had all been replaced to an overhead. The only way to look under the floor was to cut holes. Whatever obstruction was in the one unit was total. 300$#  of air wouldn't move it. I decided that somewhere under the building, there was spome kind of an obstruction and I would need to snake a new water line under. I ran fish tube to pull it back for the new service. I dug up outside the water meter pit to make the connection. I found this solid mass of dirt. I noticed it was very cold. In September. Then, I noticed that huge clumps of frozen dirt came off the dirt mass that had the form of the piping. I realized that the ground had frozen because the HVAC installer had run all the liquid/vapor lines for the HVAC units from the compressors in the outdoor space. One of the compressors was low on liquid and was super cooling. One of the other units was super cooling and the thermostat was set to 60 degrees but it was 75 degrees in the unit space. The refrigeration lines were insulated. The water service was not. I knocked off the frozen frost soil, shut off the compressor, and in a while, the water started to flow.

Zman

Recirc

Ice,

I think you are right. Not sure about the water dept. folks.

I have a tee in place and the line is a straight shot.

Carl

SWEI

did not realize the 4" was still intact

frozen and burst are two different beasts.  Spent nine days this January without water thanks to a shallowly buried main on the north side of the house we are in.  Fortunately it was galvanized so once it thawed out, all was well.  Frost depth here averages about 10" and code requires 18", but some people never learn...

icesailor

Something to remember:

Something to remember about freezing water pipes. If they are buried and the ground freezes, the freeze pressure is equal around the entire perimeter of the pipe. It should not ever split because the pressure is equal on the outside circumference of the pipe.

If the service is freezing from a shaded spot, get some mulch and cover it as deep as you can. In the spring, mulch your gardens with it. Also, if the ground is cold, and the service might be getting ready to freeze, you can often tell in the AM when you run cold water. If the water is so cold that it hurts, it is probably getting ready to freeze. Or if the water comes out discolored.

Another thing about split pipes. It's the full pipe that splits because the water doesn't have a place to go. But I found that by blowing out systems with air, there may be water still in the pipe, but it doesn't fill the whole pipe. The water freezes like in an ice tray and rises up. With the ends open, there is a place for expansion.

I don't know if anyone was living in the CO house with the 4" DI Service, but if there was or wasn't, it takes a lot to finally block a 4" service. If you use a test thermometer on the water coming out of the service, and it is close to 32 degrees, it is time to let it run somewhere, The municipal water company had some places where they have bleed offs to keep the water fresh. The downstream water will always be way over 32 degrees And if it is from a well, the ground water can be quite warm, in the 40's and close to 50 degrees.

It would be a fun project to circulate that service. I have it all thought out.

SWEI

freeze pressure on a buried pipe

never thought about that - make perfect sense, of course.  Out here where things (mostly) don't freeze that much, we lack a few basics my grandparents understood quite well.



Thx...