Heater isolation tool for winterising Duetto?

I've read on Another Site that there is a Carver isolation valve tool that I should be using on the water heater. It sounds as though this is in addition to draining it down with the big screw, for which I just use a big.... screwdriver. I don't really understand --- do I need this? This is what they say on the Auto-Sleepers Owners Club website:

" For the last 4 years, during the time that the Carver Rapide water heater has been fitted, an isolation tool has been supplied with each vehicle. Once the heater is drained this isolation tool should be fitted into the lower left-hand externally accessed chamber on the outside of the water heater, concealed behind the large screw in the lower left-hand corner. Inserting this tool, thick end first, will lock the non-return valve preventing the filling of the water cylinder - the thinner section thus allowing the claws of the drain plug to fit around the tool and to allow it to be re-fitted. The upper drain screw, immediately above the aforementioned upper screw, should be left open for a good length of time to allow any residual water to drain out. If you do not have this isolation tool these are available at a cost of £9.95 + VAT inclusive of carriage and VAT from the Motor Home Service Centre on the above number. The Carver water heater, the earlier model being the Cascade, does not have the screw on the top left-hand area of the gas module cover; however the isolation tool may still be used." [You must be registered and logged in to see this link.]

I'm confused.  


Any advice appreciated!
Thanks
Jinny

My last van with a Carver water heater had one of these, supplied from the factory.

I never used it, because you only need it if you want to use the rest of the water system while the water heater is "winterised". I never did - if I used the van after winter drain-down I just carried a separate water carrier in the van rather than filling the tank.

It's not complicated to make one very cheaply (very easy indeed if you happen to have a lathe) - mine was just an aluminium rod with one end turned down a bit. IIRC someone on the forum was making them for other people on the forum only a couple of years ago.

Aaah -- many thanks. That all makes sense. I've had the van for 3 years now and being a bit of a wuss (and over anxious about getting it wrong!) I've always paid someone to winterise for storage. But I finally decided I could do it. One more question --Should I empty the loo flush tank? I read somewhere that you don't have to, but should put in antifreeze. Seems a bit extreme -- you'll have antifreeze in the cassette when you start using it again which could be weird.

Empty everything Jinny, and don't forget to run the pumps (fresh water tank and loo flush) for a few seconds after the tanks are empty. That helps to ensure there's no water left in them.

Dave

Thanks to both of you ( Gromit, your Thanks button is greyed out. )
I have run the water pump, I'll do the loo flush too and I'm also going to go for a wee spin round some corners with the drain tap open and I'll leave all taps open for store.
I presume I don't have to remove the LPG cylinders -- the guy who has done it in the past never has. I will remove the leisure battery and trickle charge occasionally.
Nearly all set. Seems very early in the year but I'm experimenting with doing a SORN until April. :(

Jinny

Leave all the taps open (including shower), it can split your taps during freezing weather if they still have water in them.