Winter Maintenance of Wastewater Pumps: A Practical Checklist

Wastewater pumps work harder in winter than at any other time of year, and they are also at their most vulnerable: residual liquid freezes in the casing, lubricant thickens, packings stiffen and seals fail. The checklist below covers preparation, routine running checks and the winter-specific measures that prevent a pump from being lost to frost.

1. Checks Before Starting

(1) Check the pump pipework and its joints for looseness. Turn the pump shaft by hand to confirm that it rotates freely.

(2) Add bearing lubricating oil to the bearing housing and check that the oil level sits at the centre line of the sight glass. Change or top up the lubricating oil in good time.

(3) Unscrew the priming plug on the pump casing and prime the pump with water (or with slurry, where that is the duty).

(4) Close the gate valve on the discharge line, and close off the outlet pressure gauge and the inlet vacuum gauge.

(5) Jog the motor briefly and check that the direction of rotation is correct.

(6) Start the motor. Once the pump is running normally, open the outlet pressure gauge and the inlet vacuum gauge, confirm that both show suitable readings, then open the gate valve gradually while watching the motor load.

2. Checks While Running

(7) Keep the flow and head of the pump within the range stated on the nameplate, so that it runs at its point of best efficiency and delivers the greatest energy saving.

(8) The bearing temperature must not rise more than 35 °C above ambient, and must never exceed 80 °C.

(9) If the pump makes an abnormal noise, stop it immediately and investigate the cause.

(10) To stop the pump, close the gate valve and the gauges first, then stop the motor.

(11) For a horizontally split casing pump, change the lubricating oil after 100 hours of running in the first month, and every 500 hours thereafter.

(12) Adjust the packing gland regularly so that leakage from the packing chamber stays normal — a steady drip is what you want.

(13) Check the wear on the shaft sleeve at intervals and replace it once wear is significant.

3. Winter Measures

(14) In cold weather, after the pump stops, unscrew the drain plug at the bottom of the casing and drain the medium completely. This is what prevents the casing from being split by ice.

(15) If the pump is to stand idle for a long period, strip it down completely, wipe off all water, grease the rotating parts and the joints, and reassemble it.

4. Preventing the Pump from Freezing

Draining is only one of several options; the right one depends on the installation and on how the pump is used.

(1) Drain the water out of the pump when it is not in use, and fill it again before use. This is the simplest way to stop frost from cracking the casing.

(2) If the pump does freeze, pour hot or boiling water into it to thaw the ice, or heat the pump casing from outside.

(3) Use a downhole pump. A pump set deep in a well is far below the frost line and will not freeze.

(4) Use an insulated or jacketed pump, with steam or hot water circulated through the jacket to keep the pump from freezing.

(5) Use a non-self-priming centrifugal pump, which simply needs water added at start-up.

(6) House the pump in a space kept above freezing — anything above 0 °C is sufficient.

Applied together, these measures keep a wastewater pump available right through the cold season, which matters most in plants where a stopped pump means an overflowing wet well within the hour.