Copyright ©2016 Paul F Greig

Caravan Water tank flusher.
When we return home from a trip I like to drain and flush our water tanks, especially if have have been out bush where the water is not always sparkling clean.
I would like to say however that we usually do not have an issue with using rural bore water, most folks west of the Great Dividing Range have little choice, they use either tank water or, in times of little rain they use bore water, we feel that if these people can use the water, so can we. 
We do use a particle filter to protect the water pump and I am always amazed at how grit and stuff can get into the water tanks given the fine screen filter it goes through!.

However, as I said earlier we do like to drain and flush the tanks and the entire water system once we get back home.
The water tank drain plugs on our van are just 13 mm in diameter, this means that when the plugs are removed the water does not rush out but drains rather slowly over quite a period of time...this got me to thinking: if the water is coming out slowly it will likely not be carrying out much debris with it, ie, sand and grit and any other contaminants, ideally the tanks should be shaken before draining but this is of course would mean removing them from the van, a big job.

There is some argument about wether water tanks should be left full, partly full or empty, my thoughts here would depend on just how long between trips, for more than two months I would drain them and leave them empty, I would then flush them with fresh water before the next trip however.

So, I have come up with a system to clean the tanks insides, using material I had sitting in my garden shed I developed a sprayer....scroll down to see what I have done

The components for the flusher can be obtained from any hardware store. Note that the fittings are of the type used for home irrigation systems, they are barbed but must have clips installed to prevent them popping off. The tap connection is followed by 2 short lengths of 13 mm pipe with a tap installed centrally, at the end I have installed an end flow fitting which allowed me to insert the 5 mm piping.
The small dimension pipe must be of sufficient length to reach right across inside your water tanks, in my case my 80 L tanks are 1200 mm from one end to the other, I therefore used a piece 1500 mm long.
At the end of the 5 mm pipe I have installed a full circle sprinkler...these can also be obtained from a hardware store for very little cost..., the type I used has a push on barbed fitting, I feel this type has a superior grip and will not blow off under pressure. With the tap turned on fully a good spray is directed from the sprinkler.
Fortunately our van has removable drain plugs, once removed the opening is 13mm and this is where the sprayer nozzle is inserted. If your van does not have a drain plug don't despair..go to the next slide.
If your caravan does not have a removable drain plug you will still be able to use the flusher by removing the filler hose, the larger on in the centre in this photo, you will also need to remove the pipe from the out hose. (in this picture there are two out outlets, you may have only one.
Ensure to apply thread sealing tape to any threaded connections when refitting.
The flusher is fitted to the garden hose and inserted into each tank via the drain plug hole. (or filler hole if you prefer). Note that these tanks have built-in baffles, these are just moulding's in the base designed to reduce water sloshing around when driving, by 'wriggling' your flusher hose you will be able to get it to reach all the way to the far side. At that point, with the water pressure up and with a wrist twisting motion slowly draw the flusher back and forward from one side of the tank to the other several times.
You will be surprised at the amount of gunk you will flush from the tanks.
Of course the water tank flusher can also be used to flush a hot water system, handy when the sacrificial anode is up for inspection or replacement.....to read about that tip, click here
You might be surprised at the gunk you will flush out, especially if it is some time between flushes.
The Website of Paul and Pam Greig - Queensland Australia
Calliope River Camp -  Central Qld - 2017
The Website of Paul and Pam -
Queensland, Australia.
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