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Does the Water Tank in a Coffee Van Need to Be Higher Than the Pump?

by debbie
(London)

Navy converted panel van coffee unit serving a morning queue of commuters on a London street

Navy converted panel van coffee unit serving a morning queue of commuters on a London street

Hi does anyone know whether the water tank onboard a coffee van needs to be much higher than the pump? our pump is position above the floor level of the water tank and we sometimes struggle with the pressure on coffee machine - could this be the issue? any advice help appreciated.

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Nov 11, 2026
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by: MobCater

Debbie, I'd look at the pump before anything else, but probably not for the reason you think. Most coffee vans use a 12 volt diaphragm pump, and those are self priming, so they will happily draw water up from a tank that sits a little below them. Having the pump above the floor of the tank isn't wrong in itself. It starts to matter when the pump has to pull water a long way through a long, narrow suction hose, or when there's a tiny air leak on that suction side. The pump then sucks air instead of water, and the pressure drops off just as the coffee machine calls for it.

So the first thing I'd check is every joint between the tank and the pump. A loose jubilee clip or a tired washer is enough to do it. If you can see bubbles in the hose, or you hear the pump chattering and racing, that's usually your answer. Check the inline strainer too, as they clog with scale and bits more often than people realise. Also make sure the tank's vent isn't blocked, because a tank that can't breathe pulls a vacuum and starves the pump.

Second, think about whether the pump is really up to the job. A plumbed in espresso machine expects a steady feed, much like a mains supply. A small pump that was fine for a hand wash sink can struggle when the machine refills its boiler while you're also running the tap. Look up the inlet pressure your machine's manual asks for and compare it with what your pump is rated at. A pressure sensing pump with a decent flow rate, with an accumulator tank fitted after it, smooths out the pulsing and gives the machine an even supply. Mounting the pump close to the tank, level with or just below the bottom of it so water reaches it under gravity, helps as well.

Third, keep an eye on your water filter or softener. A cartridge that's due a change can restrict the flow enough to cause exactly what you're describing.

When I've seen coffee vans with this problem, it's nearly always a mix of a pump that's a bit small and a suction side that lets in air. Sort both and the machine usually behaves itself.

Whatever you change, keep the hoses and fittings food grade, and have a competent electrician look over any new wiring. If your water heater or machine runs on gas, anything on that side must be done by a Gas Safe registered engineer, never yourself.

Hope that helps

David

Disclaimer: This is based on my experience in UK mobile catering. Rules and costs can change, so always do your own research and check with the relevant authorities before committing.

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