A Little Icing On The Scuppers

Iced - Up Scuppers on a Flat Roof

A couple of days ago we had a small ice storm (January, 2018). Rain, at +6C, transitioned to freezing rain around 0C and the ice started accumulating on the roof in front of and inside the drainage scuppers and down the drainage "rain chains", as the weather got colder.  It also accumulated on the solar panels as well.

Frozen rain all the way up
 to and through the scupper

We have eight scuppers. All are partially blocked / iced-in, several are mostly blocked and a couple are completely iced / blocked.

The first time this ice blockage happened I rushed up to the roof with kettles of boiling water, a heavy duty hairdryer, and a bucket of anxiety laced with a pint of adrenaline. We got them open, with some effort.

Hindsight being 20/20 I now use Plan B.

Following consultation with the manufacturer of our white TPO roofing material, it has been determined that TPO is not sensitive to common salt : NaCl, especially in the clumped form used in domestic water softeners.

A heap of salt.

So today I carefully deposited about 3 litres of water softener salt upstream from / on top of each scupper.  The 3 L volume is based solely on the capacity of the windscreen washer container that was pressed into service to carry the stuff up the ladder.  

The standard 3L container

This is a "3 L" session: a bit larger than "several hands-full", or a "litre (yoghurt) container", but smaller than a gallon or half a bag of salt. 

As the weather warms and in time, the salt will burrow down and melt the ice that plugs the scuppers.  Any spare salt will hang around keeping the water near the scupper a bit saline and liquid and flowing.

Salt within the scupper proper.

In a couple of the scuppers I actually put a handful of salt directly into the opening of the scupper. Safe access was the determining factor.

I might need to add more salt later in the winter, especially if we get another freezing rain / ice event. 

I can see one of the scuppers from my office window, in some detail, and can monitor progress, or the lack thereof.  This one is the "canary in the mine", and 

the indicator of risk.

I will concede that this is not the first time I have used salt in the scuppers.  For the first 2-3 years we were here I would add about half a bag to the front of each scupper in December when access is easy and distinctly safer. Never had blocked drain problems.  

Last winter I was away for the snowy part of it: no problems.  Likely by good luck and not good management.

This winter I was slow off the mark, and for my sins, had to remedy the problem in arrears and under more arduous conditions.  

Next winter I think I will revert back to the "half bag in snow-free December" system.