Pumps
Pumps
The category holds three groups together that differ more than the shared name suggests. Dirty water and drainage pumps are submersible, run off the mains, draw between three hundred and twenty and two thousand two hundred watts, and the strongest gives a thousand litres a minute. Diaphragm and spray pumps work on twelve volts, stand outside the liquid and draw it up themselves. The third group is made of small circulation pumps on twelve and twenty-four volts, with a brushless motor, fourteen or twenty-six watts drawn and seven hundred to eight hundred litres an hour, which is a little over thirteen litres a minute.
The first question is not how much the pump gives but what will go through it, because the liquid decides before the power does. Clean water, cloudy water carrying sand, diesel and spray mix want a different impeller, different seals and different materials. The range shows it plainly, because of the small twelve-volt pumps only one is meant for diesel and says so in its description. On the others the description makes no such promise, so they have no business near fuel, however alike they look.
The second question is where the pump will stand, and the answer cuts the range in half. A submersible pump has no suction side, because it sits in the liquid itself and only pushes it upwards. A self-priming one stands outside and has to lift it first, which atmospheric pressure allows to ten metres at most and in practice rather to six or eight. That is why a flooded cellar gets a submersible pump and a water butt a self-priming one.
The third thing is the voltage, and it is often read wrongly, because the figure on the plate belongs to the pump and not to the socket. The twenty-four-volt circulation pump has a mains adapter in the box, so you plug it into the wall, but it runs on twenty-four volts DC itself and just as happily off a battery. Twelve and twenty-four volts cannot be swapped, though, because a twenty-four-volt pump on twelve volts runs at roughly half speed and often will not start at all. The other way round is worse, because a twelve-volt motor overspeeds on twenty-four volts and the winding insulation will not take it.
The small pumps all carry IP68 protection, only IP68 on its own does not say how deep. The eight is the one grade in IEC 60529 where the depth and the time under water are set by the manufacturer, and the standard asks only that they be harsher than for IP67, that is more than a metre. So before you drop the pump to the bottom of a deep tank, look up the actual depth in its description, because two pumps with the same IP68 can differ by metres.
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