Water systems in motor homes and caravans

Truma Water Systems Guide

The most important features at a glance

Bathrooms and kitchen units have long been standard features in motor homes and caravans. The vehicles contain an elaborate water system so that sufficient cold or hot water flows from the tap when you need it. Individual accessories can be retrofitted or replaced. Here, we present a typical water system with all the important components.

Water tanks

The choice of water tanks is as varied as the range of caravans on offer from the manufacturers. In caravans, fresh water is either carried in a canister or transported in a water tank. This tank is either fixed or mobile. Mobile tanks have rollers that allow them to be pulled easily to the water tap. For example fixed water tanks are filled via a water inlet outside the vehicle.

The volume depends on the size of the caravan, among other things. Small tanks hold about 25 litres, larger water tanks have capacities of up to 70 litres. In some caravans the fixed tank is installed, insulated and heated beneath the floor. But they can also be installed under the bench or under the sink.

In motor homes, clean water is mainly kept in a fixed water tank. This is filled via an outside nozzle. Depending on the space in the motor home, the tank can hold between 40 and 200 litres of water.

All water tanks and canisters must be made of high-quality material that is suitable for drinking water.

Tips for the water tank

  • In order to prevent germs, water tanks should be emptied, cleaned and disinfected regularly, as well as when they have not been used for some time.
  • Before you add fresh water, the tank must be completely empty. Remaining water is shaken out if you drive a short distance with the tap open.
  • For water treatment, we recommend chemical and biological additives from specialist outlets and drinking water filters for the piping.
  • The freshwater tank must be emptied in winter so that no frost damage occurs.

Water pumps

Water is pumped from the tank through a piping system into the water heater and then to the withdrawal points in the vehicle. A water pump ensures that water flows through the pipes. In the camping area, two different types of pump have become established.

submersible pump is suspended directly in the water tank. When you open a tap in the vehicle, a micro switch in the tap starts the pump and the water flows. Submersible pumps are used mainly in caravans.

On the other hand, pressure water pumps are used more frequently in motor homes. They can be installed anywhere in the water system and maintain constant pressure in the piping. When a tap is opened, the pressure drops and the pump starts. Pressure pumps are generally more powerful than submersible water pumps – but they are also more expensive. However, they usually last longer. Individual parts can be easily repaired or replaced. Pressure water pumps have one big disadvantage compared to submersible pumps: if the system has a leak, the entire water tank can empty into the vehicle.

Tips for water pumps

  • If you want to shower in your vehicle, the water pump should pump at least 10 to 12 litres of water per minute.
  • Do not allow a submersible pump to run dry for an extended period: the pump can overheat and break down completely.
  • Regularly clean the pre-filter of your pressure pump.

Water pipes and hoses

In hoses approved for drinking water, fresh water is transported in both systems (hot and cold). Hot water hoses are available in red or colour combinations, hoses for cold water are blue. Pipes are installed so that they are easily accessible. This allows you to recognise and repair leaks quickly.

Dirty water generally flows through a spiral or corrugated hose. This is connected to a wastewater tank or canister with a screw connection.

Tips for water pipes

  • Leaks in hoses and pipes occur less frequently if you avoid branches in the piping system.
  • Check pipes regularly for leaks.

Water heater

In most caravans and motor homes, an appliance to heat water is integrated in the water system. Various water heaters are available depending on the requirements. 

A Therme uses the existing warmth from a caravan heater to heat the water. This saves energy and you always have hot water available when you heat the vehicle. If the heater is not being used, water is heated with an electric heating element. A professional can retrofit a Therme in your caravan with little effort. 

A boiler holds more water than a Therme. If you use the shower in your caravan when you are on holiday, you will need a boiler with a volume of at least ten litres. These can be installed in caravans and motor homes. Boilers run on electricity, gas, or a mixture of gas and electricity. 

Combination appliances
With a combined heater/water heater you have a warm vehicle and also sufficient hot water. The integrated water container holds ten litres. A combination heater such as this allows both functions to be used together or separately. You also save space and weight in the vehicle. Whether you have a caravan or a motor home – combination appliances are suitable for

Installation overview Truma water heater


Water systems in caravans and motor homes also include all the fittings in the kitchen and bathroom. To save weight, taps used in camping are made from lightweight plastic. Like in your bathroom at home, the cartridge inside a mixer tap is the core of the fitting. The cylindrical insert, made from plastic with two ceramic discs, ensures that water has the right temperature when it flows form the tap.

Tips for fittings

  • Ceramic cartridges can usually be replaced without having to replace the complete fitting.
  • Frost can damage fittings in the vehicle. When you empty the water tank, adjust the mixer tap to the middle setting (hot/cold) and disconnect the water pump from the power supply. This ensures that no more water can flow through the pipes into the tap.

Wastewater tank

Like with freshwater tanks, there are also mobile tanks and canisters and fixed tanks for wastewater. The latter are either installed beneath the vehicle, inside or in the access floor. Slightly dirty grey water from washing hands, showering or washing dishes flows into the wastewater tank.

Campsites have special disposal facilities for dirty water. You take mobile tanks and canisters to the disposal facility yourself and empty them there. With fixed wastewater tanks, you park your vehicle at the marked place, connect a wastewater hose to the nozzle and hang the hose into the drain. Then open the drain valves for grey water.

Tips for wastewater tanks

  • Clean the wastewater tank regularly with chemical cleaning products from specialist retail outlets.
  • Do not allow the products to remain in the tank for longer than specified by the manufacturer so that it does not attack the piping or tank material.