Finding a Frozen Spot on a Pipe

[Manguy888]

We recently had our oil fired steam radiators removed and replaced with gas fired hot water baseboards. This has been one of our best decisions ever: warmer house, lower bills, no more clanging pipes (and goodbye asbestos!)

There's only one issue: the second floor zone does a loop all around the upstairs space, including some uninsulated knee-wall spaces (these spaces are common in old new England houses with steep roofs). On cold days, usually 0F or below, the pipe freezes somewhere and our heat stops upstairs. Our only recourse is to wait until it gets warmer, or open all the doors to the uninsulated spaces and crank the heat downstairs.

It's all PEX so there's no worry about burst pipes, but I'd like to insulate better or use heat tape to prevent this from happening. Problem is, I have no idea where in the loop the pipe is freezing. Does anyone know a method to find the frozen spot? I can crawl around and access about 90% of the run.

[Spork]

I'll bite.  Someone will probably have a better idea though.

Can you take an adhesive tape thermometer (like this) and measure the temperature of the pex?  I don't really know the insulating quality of the pex itself, but you might be able to tell if it was below freezing.

I'd wildly guess to start at the farthest end from the heat source.

[worms]

Could you not just add an antifreeze inhibitor to the circulating central heating water?

[LadyStache]

There are infrared cameras that can detect the cold spots. Some Home Depot stores rent them out.

http://www.flir.com/homedepot/

[Greg]

Heat tape and PEX don't mix.  If the tubing is visible, you can use an IR thermometer (no-touch thermometer) on the tubing to find the frozen spot.

[GuitarStv]

Could you not just add an antifreeze inhibitor to the circulating central heating water?

I like this suggestion an awful lot.

Couple that with crawling around and insulating any part of the pipe run that is in a cold, reachable space and that's about the best you could hope to do.

[Posthumane]

Heat tape and PEX don't mix.  If the tubing is visible, you can use an IR thermometer (no-touch thermometer) on the tubing to find the frozen spot.

I'm not sure why you say this. My house (along with every other house in my area) has PEX as the main supply line running through an unheated crawl space under the house. Heat trace is present on all of them, as well as pipe insulation, since we get temperatures below -30C in the winter time. Most PEX piping is rated to pretty high temperatures, much hotter than typical heat tape.

The IR thermometer suggestion is a good one. If you have access to the pipe you can also try flexing it in different spots and you may be able to tell where the hard spot is. When my water supply froze a couple of times due to a heat trace failure the point that it froze was at the shutoff valve, which is brass and a much better heat conductor than PEX.

[Manguy888]

Thanks for all of the advice - I'll be finding an IR thermometer asap.

In regard to the antifreeze comment, this idea is so good (and so commonsense) that I wonder if there's some reason isn't used. Does the antifreeze inhibitor not play nice with some of the equipment (circulator, valves)? Otherwise I'd think it would be standard in every installation in New England.

Good point about the brass shutoff valves as well. The installers of my system used these rounded metal braces to guide the PEX around each corner of my house. The mixture of metal being a good cold conductor and the fact that these corners weren't insulated tells me they could be the issue.

[Posthumane]

Most antifreeze also has corrosion inhibitors in it so it is usually beneficial to most metal parts in the system. Of course you can only use it if it's a closed loop system. If you're going to put some in, I suggest going with something relatively non-toxic such as propylene glycol.

[Manguy888]

I'll double check, but I'm 90% sure it is a closed loop system.

dumb question alert: if the system is closed, where would I add this antifreeze?

[Bob W]

Insulate the Pex.

[ShoulderThingThatGoesUp]

Thanks for all of the advice - I'll be finding an IR thermometer asap.

In regard to the antifreeze comment, this idea is so good (and so commonsense) that I wonder if there's some reason isn't used. Does the antifreeze inhibitor not play nice with some of the equipment (circulator, valves)? Otherwise I'd think it would be standard in every installation in New England.

Good point about the brass shutoff valves as well. The installers of my system used these rounded metal braces to guide the PEX around each corner of my house. The mixture of metal being a good cold conductor and the fact that these corners weren't insulated tells me they could be the issue.

Plastic PEX corner rounders are available, which I know because they're installed next to the manifold in my house.

[Posthumane]

A closed loop system has to have drain/fill valves somewhere, since at some point it had to be initially filled and they have to be occasionally drained for maintenance. It should also have an expansion tank somewhere since the working fluid expands and contracts as it heats/cools. I imagine these would generally be located in an accessible area along with the pump, thermostat, and other hardware.

[James]

Anti freeze isn't a horrible idea, but please don't use that as a solution to the problem. Think of all that lost heat!!! And don't use heat tape, that would just add even more heat loss!


Insulate all the areas, both the pex and surrounding area. If well enough insulated you won't have any problems. The thermometer is a great way of finding problem areas after you insulate, but you don't want to limit your insulation to areas that are actually freezing, insulate all areas that aren't adequately insulated.