I have an onboard tank which now doubles the cold water we have available when using the aquaroll. It is filled via the aquaroll but just gives us that extra when using the shower when we are on a site with no facilities. My wife loves it because the time she takes to rinse her long hair means we never run out at an inconvenient time.
We have had tanks for the last 17 years DIY fitted until the Oklahoma
We always travel with the tank just full until the low level light goes out and that means less rushing on arrival at a site especially if its raining and there is water available to brew up/wash hands etc en route
People say that it can cause instability but we haven't found that
Its 20lb of water in a ton of caravan .
We also like the extra water available to pump in from the aquaroll when showering
I find the smaller aquaroll just fills the tank when the low level light comes on
I have a pump saver switch on the fill tank pump and so it cuts out just as the aquaroll is empty
My Royale has two on-board tanks, but I've never used them. I don't see the point of pumping water twice,once out of the Aquaroll into the tank, then back out of the tank into the kettle(or whatever) Pumping straight out of the Aquaroll saves time and battery power.
The point which has been made twice in a few postings is that you have not an aquaroll full but a tank and an aquaroll full that can be usec to increase the capacity of water available when showering
It also means the its not essential to refill the aquaroll at the exact moment when it runs out which is good if its asummer like the last one
Water is also available for use on tow as explained above
Those are some of the reasons but if they don'e suit anyone then there is no need to change the ways that do.
We put about 5 litres in the onboard tank so that there is enough for a cup of tea etc en-route and on arrival at a site.
As we always use showers on the site there is no need for the aquaroll which we leave at home and the onboard tank holds 40 litres. It is easy to fill up with a watering can which is lighter and smaller than an aquaroll.
My experience with fixed on board tanks is not good. The submersible pump in the tank constantly needed to be hooked out and re-primed, and it was very difficult to clean out thoroughly.
Since those days I've always fitted a removalble on-board tank in the form of a 20l container and a second pump connection (availalble from Whale). This means we have water en route and overnight if it's cold and freezing e.g. going down to Spain in the winter.
The container is easy to remove for cleaning and fits neatly below the fixed bed, quite close to the axle so not affecting the loading significantly.
We had one on our last van, Avondale Osprey and on our new Fleetwood Heritage.
The Avondale system used two pumps and we found that it was very simple to operate either from the aquaroll or from the tank. The system could also be used in "auto" mode where the onboard tank filled as required.
The Fleetwood system uses just one pump and is not so easy to use. There is no cut out on the tank fill, so if your not standing there watching it you lose your water out of the overflow.
You also have a valve position to change and a solenoid to operate to run the system.
So in short find out how the system works before you buy!