Most premature pump failures trace back to the installation, not the pump. Air leaks on the suction side, an undersized inlet, a pump left to bake in the sun, or a first start-up run dry — all avoidable, all common.
Electrical work. Plug-in pumps connect to a suitable outdoor-rated socket on an RCD-protected circuit. Any hard-wiring, new circuits or switchboard work must be done by a licensed electrician in accordance with AS/NZS 3000. Plumbing connected to a potable or mains-connected supply may also need a licensed plumber — check your state’s requirements.
Before you start
Confirm the pump suits the job. Total dynamic head and required flow should already be worked out — see Understanding Flow Rate, Head and Pump Curves.
You will need: suction pipe and fittings sized to the pump inlet, a foot valve or non-return valve, thread sealant tape, hose clamps, a level, and a bucket of water for priming.
Step 1: Choose the position
Get the pump as close to the water as possible, and as low as safely possible. Every metre of suction lift and every metre of suction pipe costs performance and makes priming harder.
Requirements for the position:
- Firm, level base. A concrete pad or paver. A pump on soft ground vibrates itself out of alignment and stresses the pipework.
- Above flood level. Surface pumps are not submersible. Even the IP-rated models are not designed to be underwater.
- Sheltered. Out of direct sun and rain. UV degrades plastics and seals; heat shortens motor life. A simple pump cover or small enclosure is enough — but it must be ventilated, because motors need airflow to stay cool.
- Accessible. You will need to reach the priming plug, the drain plug and the electrical connection.
- Away from bedrooms. Pumps are noisy on start-up. Consider where the noise lands, especially with automatic controllers that may start at any hour.
Step 2: Build the suction line
This is where installations succeed or fail. On the suction side the pipe is under vacuum, so any imperfection pulls air in rather than leaking water out — and air is what stops a pump priming.
Never reduce below the pump’s inlet size. The RM-JP100 has a 1” inlet, so 1” is the minimum. On runs over about 10 m, or where suction lift is significant, go one size larger than the inlet.
Keep it short and direct. Every bend adds resistance. Use long-radius sweeps rather than sharp elbows.
Rise continuously toward the pump. The suction line must slope upward the whole way with no high points. A dip followed by a rise creates an air pocket that will never clear, and the pump will never prime properly.
Seal every joint properly. Thread sealant tape on threaded joints, correctly rated solvent cement on PVC, and double hose clamps on barbed fittings. A joint that holds water under pressure can still admit air under vacuum.
Fit a foot valve at the water end, below the surface, with a strainer. It holds the prime between runs so the pump does not start dry. Keep it at least 300 mm off the bottom to avoid drawing sediment, and at least 300 mm below the lowest water level so it never sucks air.
Never use lay flat hose on the suction side. It collapses flat under vacuum. Lay flat is a discharge-only product — see Choosing and Using Lay Flat Discharge Hose.
Suction line checklist
| Requirement | Why |
|---|---|
| Same size as inlet or larger | Undersized pipe starves the pump and causes cavitation |
| Continuous rise to the pump | Prevents trapped air pockets |
| As short as practical | Reduces friction and priming time |
| Airtight joints throughout | Vacuum pulls air through any gap |
| Foot valve with strainer | Holds prime, keeps debris out |
| Rigid pipe, not lay flat | Lay flat collapses under vacuum |
Step 3: Connect the discharge
The discharge side is easier — it is under pressure, so leaks are obvious.
- Fit an isolation valve near the pump so you can service it without draining the system.
- Fit a non-return valve on the discharge if the system feeds a tank or elevated storage, to stop backflow through the pump.
- Include a union or flexible connector so the pump can be removed without cutting pipework.
- Support the pipework independently. Its weight must not hang on the pump body.
- Consider a pressure gauge at the outlet. It makes commissioning and future fault-finding far easier.
Where you are fitting a pressure tank or an automatic controller, do it now — see Pressure Tank or Pump Controller?.
Step 4: Prime the pump
Running a pump dry, even briefly, damages the mechanical seal. Never switch on before priming.
- Close the discharge valve, or leave one outlet open depending on the pump’s instructions.
- Remove the priming plug on top of the pump body.
- Fill the pump casing and the entire suction line with clean water. This is the step people rush. Keep filling until water sits at the priming port with no more going in.
- Replace the priming plug and seal it.
- Open the discharge valve part way.
A jet pump with a properly filled suction line and a working foot valve should prime within 30–60 seconds. If it has not moved water after about two minutes, switch off. Running longer will cook the seal.
If it will not prime
| Symptom | Likely cause |
|---|---|
| Motor runs, no water at all | Suction line not fully filled, or foot valve stuck |
| Primes then loses it between runs | Foot valve leaking, or an air leak on the suction side |
| Draws briefly then stops | Air pocket at a high point in the suction line |
| Noisy, rattling, erratic flow | Cavitation — suction line too small, too long, or lift too high |
To find an air leak: with the pump running, brush soapy water over each suction joint and watch for bubbles being drawn in.
Step 5: Commission it
Once water is flowing steadily:
- Check for leaks at every joint under pressure.
- Listen. Smooth running, no rattling or gravelly noise. Rattling means cavitation, which will destroy the impeller if left.
- Check flow at the furthest outlet. If it is well below expectations, revisit pipe sizing.
- Check the pressure gauge stabilises rather than fluctuating wildly.
- Confirm automatic operation. If a controller or pressure switch is fitted, open a tap and confirm the pump starts; close it and confirm the pump stops within a few seconds.
- Feel the motor after 15 minutes of running. Warm is normal, too hot to touch is not.
Step 6: Set it up for the long term
- Fit a run-dry protection device if the pump does not have one. Tanks run out; a RMPC-10 or RMPC-30 controller includes run-dry protection as standard.
- Insulate exposed pipework in frost-prone areas, and add a drain point at the lowest part of the system.
- Record the model, serial number and installation date, and keep the manual with them.
- Set a reminder for the first service — see the Water Pump Maintenance Schedule.
Common installation mistakes
Suction line too small. The most frequent error. Match the inlet size at minimum.
Pump mounted too high above the water. Beyond 7–8 m, no surface pump will prime reliably.
Air leaks on the suction side. Invisible, since nothing drips. Check with soapy water.
No foot valve. The pump loses its prime every time it stops, then runs dry on the next start.
Pump left in the weather. Sun and rain halve the service life of an otherwise good pump.
Dead-heading the pump. Running against a fully closed outlet with no relief. The water in the casing has nowhere to go, heats rapidly and destroys the seal.
Skipping the prime on first start. One dry start can damage a seal permanently.
