Why do you need an Insulation Resistance Test?
If you want to avoid unnecessary cost and inconvenience, let alone disruption to the comfort of your home due to pump failure, regular maintenance and testing of your home sewage pump is crucial.
Watch this short video to understand how an insulation resistance test can protect your home and alert you early to a problem with your pump.
What is an Insulation Resistance Test?
An Insulation Resistance Test measures the total resistance of a product’s insulation (in this case, a sewage pump). The test involves applying a pre-determined level of voltage to the sewage pump and there will be a minimum acceptable value of resistance for a sewage pump to pass the test.
There are two types of insulation in a sewage pump; insulation of the motor and insulation of the cable which is providing power to it.
The Insulation Resistance Test measures the health of the insulation between the copper wiring and the earth.
Motor coils are generally coated in shellac which insulates the copper wire, protecting it from itself and from the motor casing. This insulation prevents the voltage/power supply from being lost to earth i.e. keeps it contained. A Residual Current Device (RCD) is used to measure the earth leakage in a circuit.
Resistance test readings and what they might mean
| 999 MΩ | New Pump |
| 999 – 100 MΩ | Normal Operation |
| 100 – 1 MΩ | Plan for replacement |
| 1 – 0.01 MΩ | Failure Imminent |
| 0 MΩ | Pump Failed |
Low insulation resistance will cause the motor to draw higher current (it thinks it needs more because its losing electricity) and will eventually result in motor fail due to an open circuit on the motor stator (static bit) coils.
Any electrical appliance/machine will always degenerate over time due to heat.
There are two key reasons why insulation resistance reduces;
- Age and heat (heat generated by the motor)
- Moisture ingress into the motor – this degrades it faster and is why you should always have a cover for your pump – especially if it is outside.
Peace of mind with PASLR Servicing
If you have a home water pump or a sewage pump on your properly, PASLR can provide you with programmed servicing and testing of your pumps. We record the readings of each visit and maintain a history of the state of your pump/s, which means we can help you plan ahead if there are signs of potential failure to avoid inconvenience and unnecessary costs (due to emergency call out for a failure). We will also remind you when servicing and testing is due and we’ll give you a full report after every visit.
FAQ’s
How long is my pump going to last?
Pump lifespan isn’t one-size-fits-all. Factors that will impact the length of a pump’s life are:
- Pump type and quality – higher-quality brands and correctly sized pumps generally last longer
- How often the pump runs – pumps that cycle on and off constantly wear out faster than those that run efficiently
- Water quality – sand, silt, iron, or aggressive water can shorten a pump’s life if filtration isn’t in place
- Wastewater pumps deal with solids, grease, wipes, and debris, which all increase wear
- Installation quality – incorrect sizing, poor wiring, or bad pipework can significantly reduce lifespan
- Ongoing maintenance – simple checks and regular servicing can improve your pumps’ working life
- Electrical condition – moisture, heat, and age slowly break down motor insulation over time.
If the pump is still running, do I really need a new pump?
‘Still running’ doesn’t necessarily mean ‘still reliable’. Many pumps continue to operate past their most efficient lifespan.
How likely is it to fail tomorrow? A pump can appear fine while hidden issues are developing behind the scenes. Electrical insulation slowly breaks down over time, internal components wear, increasing heat and load, efficiency drops, causing longer run times. Small faults grow until they cause sudden failure.
When pumps fail, it’s usually without warning. Think of it like tyres – your car might still drive on worn tyres, but waiting until they fail isn’t smart or safe.
How often should I have my pump tested?
For most properties, having your pump tested once a year is a good rule of thumb, however the ideal frequency depends on how critical the pump is and the environment it operates in.
More frequent testing (every 6 months) is recommended for commercial pumps, older pumps, and some wastewater pumps, especially where failure could cause flooding, sewage overflow, or downtime, or where pumps operate in damp or harsh environments.