I had a WB condensing combi installed three years ago. It replaced an old conventional boiler which was located on the outside wall of my attached garage.
Because of the location, there was no accessible internal drain available, and so the condensate pipe had to be taken out through the garage wall where it descends vertically for about 14" before running beneath the concrete path at the side of the garage and terminating in a proper condensate soakaway.
That final 'run' is just three feet long and the pipe is just a couple of inches below the surface of the path and poorly insulated. The reason for the poor insulation is that I had to cut a channel for the pipe in the concrete path and the concrete was bloody tough! I did not cut the channel deep enough to enable insulation to be completely wrapped around the pipe - and so I slit a length of pipe insulation lengthways and laid this over the top of the pipe before filling the channel in with mortar. So, whilst there is insulation over the top of the pipe, there is none underneath it.
There was no problem for the first two winters, but last year, during the very cold spell, the external pipe froze up (not exactly sure precisely where in the run this happened) and shut down the boiler. I was able to unfreeze the pipe using kettles of hot water poured over the top of the path along the channel, and I then laid bin liners full of old towels and sheets over the top of the external pipe run - and this stopped the pipe from freezing for the rest of the winter. It didn't look very pretty, however, and the wheelie bin had to be dragged over the top of the bin liners on bin day!
Before winter sets in this year, I want to do a proper job. I don't want to be messing about with kettles of hot water at 10.30 pm on a freezing winter's night again!
Two alternatives: I can improve the pipe insulation, or I can install a trace-heating cable. The latter solution is fairly pricey, however, and I don't want to go to that expense unnecessarily - particularly as the conditions last year when the pipe froze up were exceptional, in terms of the sub-zero temperatures lasting for a prolonged period.
The short 18" vertical run on the outside of the garage wall is not a problem because I have completely wrapped that in pipe insulation and also boxed it in using some left-over upvc (soffit!). I'm fairly sure that that insulation will be protection enough.
So, if I get to work with my club-hammer and chisel, and enlarge and deepen the channel in the side path to enable me to completely wrap the pipe in heavy-duty 22mm sealed-cell foam pipe insulation, will this be sufficient to prevent a repeat of last year's freeze up? How effective is foam pipe insulation in preventing external pipes from freezing in sub -zero temperatures?