We have a fully winterized building, with a 2000-gallon holding tank for grey and black water. With only summer usage, our tank is normally pumped 3 times a year. We are hesitant about using the cottage in the winter because we believe the contents of the tank, buried only inches below ground level, would freeze and be impossible to pump out until spring thaw. Is there anything we can do to change this situation so that the contents could be pumped out during the winter if required?
–M. Pettam, Toronto, Ont.
As long as the truck can get down your road, winter pump outs are not a problem. “We have several cottagers who use holding tanks year-round,” says George Shepherd of Shepherd Septic Service in Coboconk, Ont. Other septic pump-out companies told us the same thing.
That’s not to say it won’t freeze – it probably will especially if you’re using it sporadically and there’s no hot water going into the tank to keep the contents liquified. But haulers come equipped to break through surface ice.
To reduce the likelihood of freezing you can insulate your tank. A five-centimeter layer of Styrofoam SM on top of the tank is equivalent to about 60 cm of topsoil. You could even put insulation down the side walls for added protection.
Holding tanks should be equipped with alarms (usually one visible and one audible) to warn you when they are nearly full. To be safe, you should always do periodic visual inspections of the level. (You may need to clear some of the snow and soil to get at the access hatch.) In the winter, have the tank pumped out when it reaches three quarters capacity. Otherwise, you run the risk of the contents freezing, expanding, and then cracking the the tank. If the tank is filled to capacity, effluent could back up into the pipes, which could burst if their contents freeze.
That said, it’s possible to use your holding tanks all winter long without pumping out. The key is to pump the tank late in the fall, then be extra vigilant to reduce the amount of water that is flushed into it.