When I installed the electric water pipe heating I thought I was done. Until the temperature hit -22°C. We had that temperature for about 2 days and when that happened it resulted in a frozen water pipe.
Water pipes inside the house
The former owners of the house dug a new water line years ago and build a small hut around the house entrance point. Combined with in-pipe heating this was a state of the art system back in the 90s. My wifi temperature logging showed me that the newly insulated points are all fine. So we got an Infrared Thermometer (Amazon DE, Amazon UK). With that we were able to check the in-house piping system. We found some points near freezing or even below 0 which were to near to the floor or to the wall. We insulated them with a little styrofoam, just to make sure that they have no contact with the cold wall or floor. We also used an electric heater to warm up the too cold points. But still we had no water running.
Water pipe outside
Within the hut I had to dig deeper. I removed the wooden floor in order to get below it. I then found that the pipe wasn't insulated between what I insulated and the point it hit the ground. I used the Infrared Thermometer to check the temperature of the water pipe, and it was -6°C. Equipped with a hair dryer I started unfreezing the pipe. After some minutes the thermometer showed +° and I couldn't feel any hardness inside the pipe. But still we had no water running.
I started to examine the ground and found that there was no actual soil around the pipe. Instead I found a mixture of Styrofoam and mineral wool. The mineral wool was completely frozen. I guess what happend was that the water which was leaking from the now fixed T-Connector ran down and the Mineral wool soaked it up. Once the temperature dropped it started to freeze easier than soil. So, Lumia and I started to remove all that "insulation" until we reached ground at about 1.5 meters. Removing all that stuff took us about 2 hours. With the thermometer and checking the pipe by hand we then found the frozen part of the pipe, heated it and after some minutes had the water running.
Using a fan heater
We didn't have any additional pipe insulation around so we used a fan heater over the night. On the next day we went to Bauhaus in Tampere to get PE-foam insulation and additional Styrofoam pipe insulation. At Motonet we bough 6m of electric heating cable. We installed it and we should now be ready for the next -22°C. Hopefully!
Thoughts about the hut
The hut inside which the water pipes enters the house is pretty decently made. In order to have access to the water pipe at all time we are looking into building some kind of cellar with a concrete floor. As the pipe itself is now insulated we don't need to fill up all the way from the bottom to the top with insulation. We also need to remove more of the old "insulation" of which there still is quite an amount above the water pipe outside the hut. We can't do that at the moment because it would be to risky as too much snow is resting on it. It is now on our todo list and we are getting it done in Spring.