Water Tank, Filter and Pump

Sterlin is fitted with a 50 liter (13 gallon) clean water tank which is connected to an electric pump which pumps the water through a water purification or filter system.

The plan is that the water tank will always hold clean water. To achieve this, we will filter all water before it goes into the tank by using the pump and filter system. And as an added precaution, we will also filter the water when we pump it from the water tank for use.

Components

The first major component is a water tank from Front Runner which  is made from food grade polyethylene and is BPA free. Although the tank construction is very solid, unfortunately the metal outlet valve leaked and we replaced it with a new fitting. The other problem we had to address was a way to let air into the tank to replace the water which is pumped out. Unless we did this, the pump would create so much suction that the tank would collapse in on itself.  One way to address this is to merely open the filling cap when in use. But we need to remember to open and close the cap, which seems unlikely. So instead, we fitted an air intake valve into the cap.

The second major component is a water pump.  We selected the Revolution water pump from Shurflo which is capable of producing 3 gallons or 12 liters per minute at a draw of 7.5 Amps from the 12volt system. More useful is that the pump will automatically cycle on and off based on demand and will even run dry without damage. The water pump is on its own 12volt circuit with an isolation circuit so it can be turned off at night and while driving. When turned off we also relieve the built up water pressure in the hoses to prevent leaks.

The last major component in our clean water system is the filter. We selected the Doulton RIF-10 which is a 0.2 micron ceramic filter capable of filtering out pathogenic bacteria such as E.coli, salmonella etc. It will also reduces dirt, chlorine taste and odor, mold, algae and removes 100% Cryptosporidium and Giardia cysts. Typically there is also a sediment filter before the activated carbon and ceramic filters to protect them. But to save space, we did not install the sediment filter. Halfway through the trip we switched the order of the two filters, using the ceramic filter to protect the activated carbon as it is easier to clean the ceramic filter. The recommended installation order is the other way around.

The three major components are connected with various hoses, piping, valves and fittings.  The water pump and water filter system are mounted on a wooden panel with a simple detachable mount which enables them to be electrically and hydraulically disconnected and removed from the vehicle for cleaning or operation outside the vehicle.

Operation

The operation of the system is very simple.  To start the flow of clean water the outlet valve is opened, the pump detects a drop in discharge pressure and automatically starts and the water flows. To stop the flow the outlet valve is closed, the pump detects a rise in discharge pressure and automatically shuts off after a few seconds. The main trick is to avoid accidentally opening the discharge valve when the pump is enabled, which results in water going everywhere.

Filling the water tank is also a simple system. The inlet side of the water pump can be connected either to the water tank or a external source for filling. The water tank and the external source connections both have an isolation valve, which is typically closed. We connect a short piece of hose pipe to the external connection point, open the valve during the filling process. The short piece of hose pipe is long enough that we can drive our car into a river and directly fill from the river. More typically the water source will be from a hotel and we have a portable and collapsable water bag so to can carry the water from the hotel to our car.  We will have to repeat this process a number of time to fill up an empty water tank.

We will however inspect the filters every month and clean them as necessary and drain the water tank and clean it.