On board water tank

[ctj]

This has prob been covered a hundred times or more but i cannot find anything useing the search bar!!
Anyways we have just aquired a 95 swift 520 with onboard fresh water tank having never had one of these before am i ok to travel with it full or do i need to empty it brfoe traveling? Thanks

 

[GeorgeandAde]

Hi ctj.
Ive never had an onboard water tank but I prefer to travel as light as possible,so personaly,I would travel with it being empty.
Im sure there are more technicaly minded people on here who may also suggest that a "swaying motion"of the water may cause slight instability problems.
Im not sure,but its just my own personal thoughts.
Adrian

 

[Lutz]

I've never noticed any difference in the way the caravan handles whether the tank is full, half full or empty. Probably the relative mass of water swishing about is too small compared with the total weight of the caravan to have an appreciable effect. However, it's obviously preferable to have the caravan as light as possible so I try to avoid having a full tank, but it's useful to have a little inside while on the move, if only to wash hands after a stop en route.
In some cases, depending on where the tank is, it is may also be of benefit to use the contents as ballast to get the noseweight right.

 

[Mel]

Having water moving about in a tank and causing instability is called the "free surface effect" and it can be very powerful; evidenced by the capsize of the Herald of Free Enterprise. However the surface of an in board tank may not be big enough to cause the van over turn although it could just add to the difficulties if you had other factors causing instability. More importantly water is weight and weight costs more to tow. Drain it. If you want to stop for a cuppa on route take a plastic bottle of water in the car.
mel

 

[Lutz]

I have my doubts about your statements, Mel, as Adria fit two on-board water tanks on some of their models, one at the front and one at the rear, for the express purpose of using the content as ballast to adjust noseweight. Surely Adria would not have done this if stability were seriously affected?

 

[Dustydog]

My on board tank is nearly 40 litres and situated on the front offside . I litre of water weighs 1kg. That's 40kgs out your useful load allowance.
Try picking up a full aquaroll. There are no baffles in the tank. and the top access hatch is only a "flimsy" plastic lid. There is always the possibility the tank could burst under the stress and all that water over the floor wont help matters.

Personally we only tow with this tank empty. Similarly we never tow with the toilet flush tank full, maybe just a quarter and the waste tank empty.
I'm sure I read in our handbook not to travel with the on board tank full, I'll check.
IMO Mel's point is valid as the water sloshing around , from side to side cannot be good for all round stabilty.
Lutz I understand your point about ballast but unlike Adria I only have one tank.
If I did fully fill the tank I would have to rejig our current loading methodology putting more heavy things to the rear. Not for me .