How much use is too much use for a $135 water blaster?

An Auckland man has taken a water blaster manufacturer to task after pulling apart his machine to find his metal engine case has plastic gear cogs.

Jeff Davies thought he'd have a peek inside his Karcher water blaster after it stopped working.

"I thought, well I'll have a look inside and see what’s happened, and see if I can fix it."

Davies told Fair Go he understood opening the machine would void his warranty but he did it anyway. What he found worried him.

"It's beautifully engineered, everything metal apart from two plastic gears."

The gears had been destroyed, Davies believes, by overheating after 90 minutes of continuous use. He said metal cogs would last a lot longer.

However, Karcher told Fair Go the fault was more than likely caused by a failed seal or water leaking into the oil.

"With no oil to lubricate the cogs it doesn't matter whether the cogs are metal or plastic they will eventually fail," the company told Fair Go.

Davies had loaned his water blaster to a friend who claims he was told by Karcher that it shouldn't be used for more than an hour.

Karcher say they don't have a maximum usage although they note Davies' model is designed for smaller tasks like cleaning a car.

"Running the machine for significantly longer periods does bring some risk."

A water blaster repairer we spoke to agreed that metal parts are better than plastic, but metal cogs would also be damaged if the oil gets compromised around them.

Karcher said they've got happy customers with water blasters that are more than 20 years old, and they encourage Davies to contact them to "help him directly".

Davies, a home handyman, ordered his own new plastic cogs — there are no metal cogs available — and installed them. It cost him $30 and after a bit of tinkering, his water blaster is operational again.