What is the different between grey water
and black water? What types of
pumps can be used to dispense water? How many water tanks do I need?
for your caravan or RVs come in various holding capacity sizes. They
can range from 55 litre (11.5 gallon) up 127 litre (28
gallon), are normally black in colour, and the plastic type
are usually covered by a bash plate to prevent puncture.
Water tanks also come in stainless steel and as there is a
need to conserve weight when towing these are less likely to
be used in caravans.
Some RV’s have one water tank and others come with several.
Usually there is one separate tank specifically for drinking
water and at least two others for shower facilities, washing
up and general washing.
Where there are several tanks, they are
normally joined by a piece of hose or plumbing between each
to allow for multiple filling and it may be worth
considering installing a shut off inline valve, which is
similar to a tap, between each tank.
The purpose of this is
to avoid loosing the water from all tanks in the unfortunate
event that one of the tanks is punctured. Another
purpose is that you can avoid filling all your tanks if you
do not need to do so for say short trips, although care
should be taken when doing this to ensure the 12V pump
operates from the useable tank(s).
An ‘accumulator’ tank is a tank with a
bladder inside. These are often used in motorhomes. One
side of the bladder is pressurised by compressed air and the
other side contains water. The flow of water, with a 12V
pump, is smoother due to the constant pressure thereby
eliminating ‘water hammer’.
When filling a caravan drinking water tank use a food grade
hose (often white in colour) as filling the tank with a
garden hose will make the water taste somewhat ‘plastic’.
‘Grey Water’/ ‘Black’ Water Tanks
Although not as prevalent here in
Australia, some campgrounds and National Parks are becoming
more concerned with the environment and do not want ‘grey
water’ dumped onto the ground.
Motorhomes, fifth wheelers and some
campervans have three water tanks. One for fresh water, one
for toilet sewage (known as ‘black water’) and one grey
water for water collected from other drains (eg:
Regular use of the shower facility and/or
sink will often see the ‘grey water’ tank fill up sooner
than say the ‘black water’ tank.
With the demand to retain fresh water
some innovators have installed a 12V pump to use the ‘grey
water’ to flush the toilet.
There is a diverse range of water pumps
Hand operated pump –
this is located on the sink and is a plunger type, operated
by hand pumping in an up and down motion. There is
also a model called Fynspray Hand Pump which has a black
moulded nylon body with a chrome plated brass handle and
Foot pump –
this is designed for flush fitting on the floor. It is
operated by depressing and lifting your foot in a pumping
action. It is often located on the floor in front of the
12V pumps –
there is a range of either
or Flojet pumps varying
in size and flow capacity from 4.3 litres per minute to 12.5
litres per minute. Some promise smooth running without
the need for an accumulator tank and are able to run dry
without any harm to the pump. These pumps can be
located under the sink or refrigerator and are connected to
the 12V power system and the water tanks.
Most pumps have a built-in pressure
switch that activates the pump once the tap is turned on.
There is normally an electrical on/off switch located near
the sink which also must be turned on as this
activates the power supply for the pump.
12V pumps are very useful when you are
not connected to mains pressure. They are also good for
access to your filtered drinking via a separate tap located
on the sink and drawn from a separate drinking water tank
located under the RV.
Some ATV or off-road designed caravans
have a separate 12V pump enabling them to pump water from
creeks directly into their shower water tanks via the filler
on the side of the van.
Pump Control Valves
Some motorhomes have a set up where the
main pump can be isolated from the system to allow water to
be pumped from an external source or between tanks.