If you are buying a replacement for a homeowner-grade machine, the first fork in the road is a residential axial pump versus a triplex. Nearly everything else follows from that choice, including what you should expect to pay and how long it will last.

What an axial pump is

An axial cam pump, also called a wobble plate pump, has pistons arranged in a ring running parallel to the driveshaft. A tilted plate spins and pushes them in and out. The whole assembly is compact enough to bolt directly onto an engine or motor shaft with no belt, no gearbox and no coupling.

Because it mounts direct, it runs at engine speed, typically 3400 RPM. That is the key fact about axial pumps and it drives everything else about them.

What you get with residential axial pumps

• Lower cost. Fewer parts, simpler machining, and no drive components to buy.
• Smaller and lighter. Most of these pumps weigh 8 to 9 pounds. A comparable triplex assembly with its drive is bulkier.
• Direct mount. It bolts to a standard engine flange or a NEMA motor face. No alignment, no belt tension, nothing to adjust.
• Plenty for the job. A 2.5 GPM at 3,000 PSI axial handles cars, patios, fences, siding and furniture without complaint.

What you give up

• Service life. At 3400 RPM the pump makes roughly three times as many strokes per hour as a 1000 RPM industrial pump. Seal wear tracks strokes. That is the whole story, and it is arithmetic rather than build quality.
• Heat under bypass. Leave the trigger off with the engine running and water recirculates inside the pump, heating up. On an axial this happens faster than on a triplex because the pump is smaller and there is less water and less metal to absorb it. Ten minutes in bypass can cook the seals.
• Rebuild economics. Axials are technically rebuildable and rarely worth rebuilding. When it goes, you replace it.
• Continuous duty. These pumps are designed for intermittent residential use. Running one all day, every day will shorten its life dramatically.

Axial models we stock

Two things in those part numbers are worth decoding. V is horizontal and W is vertical, which describes the engine orientation the pump mounts to. SX on the end means left-hand shaft. Getting either of these wrong means the pump physically will not fit, so check your existing unit before ordering.

When to step up to a triplex

A triplex plunger pump uses a crankshaft and connecting rods with three plungers, phased 120 degrees apart. The crankcase is oil-filled and sealed away from the water. It costs more, it usually needs a belt or a reduction drive, and it lasts several times longer.

Buy the triplex if any of these are true:

• You use the machine more than a few hours a month
• You are doing any work for money, even occasionally
• You want a pump you can rebuild rather than replace
• You need more than about 3.5 GPM

We stock triplex pumps in residential sizes too, so the step up does not mean an industrial machine. The RSV3G30-PKG at 3.0 GPM and 3,000 PSI and the SJV3G27-PKG at 3.0 GPM and 2,700 PSI are both complete packages that drop into homeowner-grade machines.

Making either one last

Three habits account for most of the difference between a pump that lasts two seasons and one that lasts eight.

1. Never run it dry. Water lubricates the seals. Start the water first, purge the air with the trigger open and no nozzle fitted, then start the engine.
2. Do not leave it idling in bypass. If you are going to set the gun down for more than a minute or two, shut the machine off. This is the single most common way homeowners kill pumps.
3. Winterize it. Water expands when it freezes and a pump head is a closed cavity. Run pump saver through until it comes out the discharge, then cap the ports. Do not use automotive antifreeze, since whatever is in there comes out of the nozzle in the spring.

Browse the full residential pump range, or if you are replacing a pump and are not sure what fits, send us the model number off the machine and the shaft size and we will match it. Contact us here.