When we leave home to go boondocking, I like to have the fresh water tank full.  Really full.  Then going down the road, up a hill, around a corner, water will slosh and escape through the overflow hoses.  Then the siphoning process takes over and a third of the tank may be drained before it stops. 

Now in my old 95 Aerbus with the tank under the bed, I could watch the tank fill.  And I could watch the siphoning process drain out a full half a tank.  I am not exaggerating.  So I was able to insert a T with a short vertical extension into the apex of the drain hose as it arched in the back of the bedside night stand.  Problem solved. 

Now I admit that if I just didn’t fill it quite as full I would be OK.  And that usually only a small amount of water drains out before a swerve or a slosh breaks the suction.  But since when has good enough been good enough? 

There are several “other” (?better?) solutions to the problem, one of which you might want to consider. 

First, after the tank is full, or even just starting to overflow out the overflow hoses, take a rubber stopper (half inch at the big end), and plug up the hoses.  Works great.  Cost, less than 50 cents.  You just have to remove them when you get where you are going, or after you have used some water on the way.  The air has to get into the tank to allow water to be drawn out.  Of course you can pull out a bit of water when corked, but soon the vacuum will build up inside the tank. 

Secondly, you could replace the corks with a valve.  Just turn it open or closed rather than putting corks in and out. 

Thirdly, you could use an anti-siphon valve.  This allows air to move in and out of the tank during draining or filling, but prevents the water from draining out unless the pressure is very high- higher than the normal siphoning situation. 

Fourthly, consider using a T.  My current Aerbus is a bit unique, and getting into the water tank compartment will be difficult.  But normally one should be able to get into the compartment, find the overflow hoses, and be able to insert a T with a vertical vent that probably will have to go up through the floor.  Or accept a bit of spill inside the water tank compartment. 

For me at the moment, the rubber stoppers work very well and are nice and simple.

 

Doug

doug@rexhalltips.com