RVing 101: A Guide to Water Pumps

Having ample supplies of fresh, potable water when out on the road is a necessity many of us take for granted. Water is essential when washing hands or dishes, making coffee, flushing the dunny, or taking a hot shower. Basic systems in caravans and motorhomes consist of fresh and wastewater tanks, the appropriate pipes and fittings, and pumps to get water to where it’s needed. Extras, such as strainers and filters remove contaminants in drinking water, and heaters provide hot water for showers.

What do Water Pumps do?

To get water flowing when turning on taps, pumps provide the needed pressure to push water from the tanks, and through the piping. Most pumps are electric and are powered by on-board secondary batteries. 12-volt types are more common and rely on 12-volt batteries, but 24-volt varieties are also widespread, mainly in larger recreational vehicles.

Types of Pumps in Caravans and RVs

There are two basic types: submersible and diaphragm pressure pumps. They differ in how they work, where they are located, how much water they provide, and of course, price. Each type has its pros and cons and meets different needs.

Submersible Pumps

Most caravans are fitted with this type of 12-volt water pump. They are submersed directly in the tank. The water reaches taps, showers, and toilets by a micro switch that starts the pump motor, and an impeller that pushes water through the piping.

Submersible pumps can provide adequate water pressure and relatively good flow. And they are cheap to buy, easy to install, run quietly, and work well even with hard or unfiltered water. Another plus is that they need little maintenance. Even cheaper types have an auto shut-off system that detects damage or plumbing faults, so the chances of flooding the caravan are slim. On that note though, any part that breaks down means you’ll need to replace the whole pump.

Pressure Pumps

Pressure pumps are more widespread in larger motorhomes and RVs. They are diaphragm pumps, relying on a series of diaphragms moving quickly back and forth to create pressure. This draws water from tanks through an inlet valve and pushes it out through an outlet valve. A pressure switch inside senses when taps are open, turning on the motor.

Compared to submersible pumps, pressure pumps have almost twice the water pressure and a much higher flow rate, so water gets to taps much faster. Users can also adjust the pressure to their liking, say when taking a shower. Besides being more powerful, a 12-volt pressure pump is also more durable, doesn’t overheat, and is easily repaired. The only cons to think of are that cheaper models can get noisy and that you’ll be paying a bit more for the convenience.

Choosing a Water Pump that Meets Your Needs

There are three things to look out for when choosing your next water pump for your caravan or RV. These are the voltage they run on, the flow rate and the water pressure. The last two determine whether you’ll be getting enough water for the outlets you have.

12 or 24 Volts?

As mentioned, caravans and smaller motorhomes usually have a 12-volt water pump and this is enough power to get water through the vehicle plumbing. Larger motorhomes with more taps will be better off with a 24-volt unit.

Flow Rates

This is the amount or volume of water the pump can push. It’s measured in litres per minute or LPM and depends largely on the number of taps. A single tap system will be good with around 10 LPM. If you have a kitchen sink as well as a shower (or a two-tap system), then you’ll be looking at pumps that can provide enough water for both when on at the same time. This is between 10 and 12 LPM. Three-tap systems (with a toilet) require around 15 to 17 LPM.

Pressure

This is the force that the pump exerts on the water to get it running, both within the plumbing and out through the taps. Pressure pumps fare better in this respect, getting up to 55 PSI or roughly the same as what you get at home. They also have cut-off valves that turn the pump off if that pressure is exceeded, so there’s no damage to the system. With that said, even basic submersible pumps reach decent pressure.

Accessories Used with Caravan and Motor Home Water Pumps

Depending on the model, pumps can have integrated (or use attached standalone) strainers to clean tank water from sediment and dirt. This is a preventative measure, and if you’re in an area where the water is less than perfect, a separate filtering system also makes sense. Ensure that tanks are clean before filling up, and use a tank cleaner solution when needed.

Cut-off and tempering valves are used with pressure pumps to limit pressure and prevent accidentally flooding the caravan or motorhome, or bursting pipes and damaging hoses. Moreover, larger systems that require more pressure may have an additional booster pump near the tank and an accumulator tank to regulate pressure spikes and prevent cycling (continuous on and off operation) that can damage the pump, especially the motor.