Much of it might be hidden but the average plumbing system of a modern RV is quite a complex setup. Many will remember when the water/plumbing system of a caravan consisted of not much more than a small single water tank and a hand or foot pump that delivered cold water to the kitchen sink. Hot water was supplied by a kettle and there was certainly no such thing as a bathroom, complete with washing machine.
TANKS A LOT!
These days, of course, things are very different. Many RVs come with a complete bathroom, hot water service, a second or third water tank, cassette or black-tank toilet, an external shower, and sometimes even a grey water tank.
The advent of modern RV accessories such as washing machines has increased the demand for more sophisticated plumbing setups
Even fresh water tanks can be quite a sophisticated setup. The basic ones are usually between 60L and 80L, made of plastic, and protected with a sheet of galvanised steel sheeting. Tougher, and not requiring additional protection, are the roto-moulded polyethylene tanks, which are quite popular with the offroad brigade.
A well-protected water tank on the van’s underside
Generally speaking, an RV with a shower would have two water tanks. Some manufacturers, such as Bushtracker and Kedron, fit separate drinking water tanks but many will simply have a filtered supply, which is separate from the main taps.
Water tanks should always be protected from road debris
All fresh water tanks should be food grade. Most can be filled with a hose, or even a bucket if you’re desperate, but some RVs have a pressure connection, which means mains water supply can be directly connected to the RV. A small number of manufacturers, such as motorhome builder Trakka, have developed a system that collects rain water off the roof and drains it into a dedicated tank.
The RV industry has, in recent years, been assisted by the adoption of cross-linked polyethylene (PE-X) piping for both hot and cold water. Some readers might remember the clear plastic piping that attached to the hand pump – that is no more! The flexibility of polyethylene piping makes it ideal for both hot and cold water, and it is very easy to fit. An additional benefit is that water hammer is fully absorbed. A point of note is that when water piping is fitted underneath any RV, it should be well strapped up and out of harm’s way.
PUMPS AND HEATERS
Hand pumps are, generally, no longer fitted to new RVs. Instead, very efficient 12V water pumps deliver the water to the sink, washbasin and shower. Once very noisy, 12V pumps tend to be considerably quieter these days. Sometimes they can even offer a clue to a water leak: if left on overnight, a sharp ‘brrrr’ in the middle of the night is not only a reminder to turn off the pump, but also to look for a leak, as it may indicate the pump is trying to maintain pressure in the lines.
Few modern RVs come without a water heater of some sort. The most popular types in Australia are the gas/electric (240V) Suburban 23L unit and the smaller Truma 14L model, also gas/electric. Some motorhomes use an intercooler unit that uses engine coolant to heat the water. A more recent addition seen in some European RVs is a Truma Combi, which is LP gas-fired and not only heats the water but also acts as a space heater.
A 23L Suburban hot water system
TOILET TANKS
Although generally isolated from the rest of a van’s plumbing system, the toilet still has some relevant components. A fair percentage of RVs are fitted with a cassette toilet, usually made by either Thetford or Dometic. Both have a removable tank or cassette with an opening directly under the toilet bowl. Most toilets are, therefore, in a fixed position but Trakka is one manufacturer that has thought outside of the box. The company’s ‘Switch Mode Bathroom’ incorporates a toilet and cassette that can be remotely powered out of the way (under the washbasin) when it’s not being used.
Toilet cassettes are now a common feature in many modern vans
Once quite rare, small washing machines are now often fitted in larger RVs, usually in the bathroom but occasionally elsewhere. They, too, are quite simple to fit but do require additional water tank capacity.
Toilet cassette plumbing
In many ways, the plumbing system in any RV is quite simple when compared to, say, the electrics, but it’s vastly different to what was used in earlier times. Without a doubt, the advancements in RV plumbing have enhanced our RV style of living.
ENGAGING THE GREY MATTER
It is a total mystery to me why just about all motorhomes and fifth wheelers come with grey water tanks but most caravans do not. Do caravanners have cleaner grey water than other RV travellers?
I suspect it’s partially historical and I do understand that there are many places in Australia where watering the ground with grey water is seen to be a good thing.
However, there is a growing number of places in Australia where dropping grey water is frowned upon, in particular eco-sensitive areas. I’ve been to a couple of motorhome rallies where the showground owners requested that no grey water be dropped at all – a minor problem for those with grey tanks but much more difficult for those without.
An additional issue is that there are a growing number of caravans that are not only fitted with shower cubicles but also with washing machines, both of which use soaps and detergents.
There are several caravan manufacturers who offer grey tanks as an option and there are many cases, particularly with larger vans, where retrofitting a grey tank wouldn’t be too difficult. In theory, doing so should not affect the load capacity too much, if the grey water tank is emptied at the same time as the fresh water tanks are filled. I do understand that this assumes every caravan park and most towns will have a dump point but it’s within reason, especially if there are places where grey water is welcomed.
Another factor to keep in mind, especially with larger tanks, is shifting the weight of the water from a fresh water tank to a grey water tank. Eighty litres of water can have some effect on caravan stability if, say, moved from a forward fresh water tank to a rearward grey water tank.
WATER WEIGHT
I might be stating the obvious here, but water is a weight factor to the tune of 1kg per litre. So when doing your weight calculations, always work on a full fresh tank. Some years ago, I came across a fifth wheeler importer who, in order to get under the 4500kg limit for air brakes, de-rated his fifth wheelers. There’s nothing wrong with that per se, except that it allowed no capacity for carrying any water. His suggestion to customers was to drain the water tanks every time they travelled. In outback Australia? I don’t think so.