Evaporative Cooler Pump Sizes Explained: JRM28 vs JRM38 vs JRM50

The pump is the hardest-working part in an evaporative cooler. It runs every time the cooler is on, lifting water from the tray to the top of the pads so they stay evenly wet. When it fails, the pads dry out and the cooler starts blowing warm air. This guide explains how to choose the right replacement so you only buy once.

Quick answer

• Order the same pump that came out. Use the part number or model on the pump label (for example JRM38 or 6050812SP).
• If the label is gone, use your cooler model from the compliance plate and check the fitment list on the product page.
• Never downsize. A smaller pump may run, but it won’t wet the pads fully and cooling drops.

What do JRM28, JRM38 and JRM50 mean?

JRM pumps are a universal family of submersible cooler pumps used in many Australian coolers, especially Bonaire and Celair. The number is the nominal flow in litres per minute, so a JRM38 moves roughly 38 litres per minute.

The cooler manufacturer chose the flow to suit the pad area. Matching the original size keeps the water distribution even across every pad.

Brackets and fittings matter too

The same pump is often sold in different versions – with a side mounting bracket, a different outlet, or brand-specific leads and plugs. Check these against your old pump before ordering:

• Mounting: side bracket, base mount or clip-in
• Outlet size and direction: it must connect to your existing hose
• Power connection: plug-in lead or hard-wired (hard-wired pumps need a licensed electrician)
• Voltage: most cooler pumps are 240V

When you need a brand-specific pump

Some coolers use a pump designed only for that range, and a universal JRM pump won’t fit properly:

• Breezair, Braemar and Coolair – many models use Seeley pumps such as the Tornado. See Breezair pumps.
• Brivis – some models use a pump base and pump assembly. See Brivis pumps.
• Bonaire Durango window and portable models use their own 240V pump. See Bonaire pumps.
• CoolBreeze – see CoolBreeze pumps.

Signs your pump is on the way out

• Pads are dry or only partly wet, and the air feels warm
• The pump hums but no water flows
• Water flow is weak or uneven across the pads
• The pump trips the cooler or the safety switch

Before replacing the pump, check that the tray actually has water in it. A stuck float valve or failed solenoid valve can leave the tray empty, and the pump will look faulty when it isn’t.

Make the new pump last

• Clean the tray and the pump filter or basket before fitting the new pump.
• Scale and debris are the most common cause of early pump failure.
• Don’t let the pump run dry – check the float valve sets the right water level.

Ready to order? Browse all evaporative cooler pumps, or read our step-by-step guide to replacing a cooler pump. Not sure which one fits? Send us your cooler model and a photo of the old pump label and we’ll confirm it for you.

This guide is general information only. Always follow your cooler manufacturer’s instructions, and use a licensed electrician for any electrical work.