Septic tanks are, even from a historical point of view, the most widespread devices for the decentralized treatment of wastewater from households. How to properly prepare them for winter? The third part of the winter series on residential wastewater treatment plants is dedicated to them.
Properly winterizing a septic tank is very easy. It is enough to check whether the septic tank is in good condition, its walls or ceiling are not twisted or collapsing, and whether the hatches are in good condition. It is advisable to secure the fastening and possibly the hatch locks against snow, ice and frost so that you can get into the septic tank even when it starts to freeze.
Also check the sludge level in the individual chambers of the septic tank. You take the fan on a long enough handle, if you don't have one, a long enough perch is enough. You sink the fan to a certain depth and slightly water it. If the thick black sludge does not rise, the level of the settled sludge is lower. You sink the fan a little deeper and repeat the process. You continue until you hit the mud. You can tell how deep the perch is on the handle, you just have to estimate the depth, the anglers can measure it with a meter. Even in the first chamber, the sludge level should never rise higher than about 30 cm from the surface. If the level is higher than about half the depth of the water, it is a good idea to remove the sludge. In winter, balancing is usually complicated by snow, ice and cold, so it is better to do it in autumn. In this way, check all the chambers of the septic tank, follow the condition of the first chamber, the worst one. Septic tanks are usually designed to be removed once or twice a year. I recommend not to extend the intervals, especially if inorganic undissolved substances (mainly sand, clay, etc.) get into the septic tank. The resulting sediment "petrifies" over time and cannot be exhausted.
In case of long-lasting severe frosts, or if you do not use the septic tank much during the winter, it is a good idea to thermally insulate the hatches and cover the septic tank altogether. You can use anything that won't fall inside, can be cleaned again in the spring, will last until your next inspection and will insulate thermally. For example straw, hay, polystyrene, snow and the like.
Today, a septic tank is no longer sufficient as the only stage of wastewater treatment, it must be supplemented by another stage, for example a root treatment plant, an earth filter or a biological pond. But more about them next time.