Camper Trailers Tech Tips

hot water heater





custom hot water system
for indoor or outdoor use



     Initially I purchased a Primus hot water unit to cater for our hot water needs, however I found the Primus inefficient for what we required. It needed to be operated by two people if the water flow was turned on and off several times during the shower process. My idea was to have a hot water system that could heat itself automatically when turned on, turn itself off when the water flow was stopped, wouldn’t use huge quantities of water and could be used out in remote camping areas.


the heater unit

    Having looked at similar setups this is what I eventually put together. The main water heating unit was purchased on ebay . It is called a Red Hot Water Heater which is all I can find as a brand name. The unit is very similar to the Mercury instant hot water unit with the main difference being a LCD display built into the unit showing the water temperature. This I felt was a great advantage over similar units as you can readily tell what the water temperature is going through the unit.

    The water heater automatically shuts off if the water temperature reaches 77 degrees C. It also shuts down after 20 minutes continuous usage. However, it can be turned back on immediately but I couldn’t imagine this being a problem. On my initial run it took approx. 4 – 5 seconds for the water to go from 20 degrees C up to 44 degrees C which is more than enough to enjoy a warm shower. The horizontal window above the winter/summer switch is the viewing window for the gas light. It does not operate with a pilot light but activates itself once the water flow commences running through the unit. The unit weighs 2.5 kg.


    I also purchased a regulator and had a 2 metre gas hose made up to go onto a 2kg gas bottle. The reason for the extra long gas hose is that the gas cylinder can be some distance away from the shower tent and water heating unit.


the pump

    The next item for the system was the pump. The pump is perhaps the main piece of equipment in the system as it drives the water through the unit and draws the water from a source.

I am using a Jabsco 12volt pump as my main pump mounted on a piece of timber to provide some stability. I also have a spare pump should anything unforseen occur to the Jabsco pump. I purchased an XTrail pump which is also a 12volt automatic pressure pump which will generate up to 40psi and more than capable of operating the hot water unit.

Jabsco 12v automatic switch pressure pump

    The Jabsco Par-Mate is a 12v automatic water pressure pump with the following features:
It can run dry without damage to the pump
Very quiet when operating
Smooth water flow
Low current draw – 4.2 amp
Small and lightweight – 1.5 kg
23.3cm x 13.3cm x 8.5cm

    The pump will generate up to 36 psi pressure which is sufficient for the hot water unit to operate. Both pumps are fitted with water filters to eliminate any foreign objects from running into the hot water unit.



I then purchased a 12v plug and cable to connect the pump to the power source in the camper. The camper has several 12v outlets.



    The next step was to acquire all the necessary hosing and connections to suit both the pump and the hot water unit.


    This hosing did the job nicely and provided sufficient to use for connections and have sufficient left over to use if pumping within 16 metres of a water source (dam, river or lake etc). It is non collapsible reinforced nylon hosing used in caravans and campers.


    Next was to extend the shower hose that came with the unit so that we could run the shower hose under the shower tent from the hot water unit and up onto a hook inside the shower tent.

    Also I added to the hose a stop valve which enables the user to stop the flow of water and subsequently turn off the unit. When your ready to restart the hot water unit you simply turn the valve back on within the shower tent and the unit automatically starts up again. This is extremely convenient if your on your own.

    The hot water unit has an automatic electronic ignition which operates from two D cell batteries inside the unit. I’m told the batteries should last up to 2 – 3 years with normal use.


final result

whole unit looks like this


hot water unit $207
12v pressure pump $82
hosing  $54
hose clips  $8
gas hose and regulator $42
12v plug $7
water valve $3
shower hosing  $12
total cost  $415


 thanks to Paul McDougall for sharing this idea


april 2009