In my latest caravan, there is a sticker on the flush tank , saying to drain the tank before travelling. In all the years I’ve caravanned I have never done this. Will this be something new, should I do this?
The reason why they advise to drain the flush tank before travelling is because if the tank contains any amount of fluid in transit then you will get a bow wave from the remaining water inside which can make the caravan unstable in cross winds and going round bends etc. so removing the flush water before setting off eliminates the risk of snaking. However, at the other end of the spectrum, if you fill the tank up full then that also eliminates the possibility of the caravan becoming unstable as well because no bow wave can be created which is what I have to do each time before setting off to help to reduce the caravan noseweight to achieve the required noseweight specified by the vehicle manufacturer which is 80 kgs.
So the answer is to either have the flush tank empty or full but nothing in between that can create a bow wave in transit.
It's not so critical in a motorhome to empty the flush tank merely because there is more stability having four wheels instead of two so it's just a weight related factor that's all.
Mine (Thetford toilet) advises not to travel with a FULL flush tank, to avoid slopping contents overwhelming the tank and spilling out of tank into the interior (it's not totally sealed at the top)! A partial filled tank is OK.
I usually travel with no more than approx half full, it's NEVER been a problem (6 years, 8k plus miles!), and the toilet is always ready for use on journey for 'comfort' breaks and a day or so on site.
The weight of fluid in the full tank is pretty insignificant, it's only 8 litres (8Kg) filled to brim, compared with the weight of even a lightweight van like mine (1310kg), and as the tank is VERY narrow and mostly vertical, the effects of 'slopping' is going to be insignificant on the dynamics of a towed van, and mine is a rear bathroom!
Can't comment on Dometic toilets, as no experience, but difficult to see much difference, as principles exactly the same!
I also always travel with the flush tank 'primed' ready for use with fluid and a litre or so of water. Tend to empty it before travel if it's more than around a third full though.
The question that the OP asked was why it said to drain the flush tank before travelling so I answered the question as required as to why the manufacturer would advise that. What people do in terms of tanks being full, partly full or empty is besides the point so we really need to stay focused on the question being asked.
The average capacity of a toilet flush tank is 7-8 litres. I think the reason for not travelling with anything more than half full is to reduce the risk of the tamk mountings coming loose because of the weight plus inertia whilst moving. Unless there are additional battens fitted behind the wallboard there is limited strength in 3mm plywood.
I think from memory Bailey advise no more than half full.
Dave.
------------- Never argue with an idiot, they will drag you down to their level and beat you on experience.
Mark Twain.
Always drain the flush tank and water heater. Then we only use plain water in the flush, no additives.
The payload is narrow enough without lugging water around as well.
We do carry a flask of hot water in the car for a brew en- route should we decide to take a break.
Could be either because of weight or more likely due to the flush circuitry in the flush tank being damaged by splashing water, I'm sure I have read that the circuit board is exposed, which isn't a problem when the caravan is static.
A little off topic here..
However, a couple of years ago we didn't use our van for 18 months ( pandemic ). reason.
Anyways during winter had a pop up to storage site just to get out of house, thought I would check on the van. Freezing cold I might add.
Low and behold I had left some tinned food in a cupboard. Not a usual thing I do, but for some reason or another I had.
What did I find! two of the tins of tomatoes had popped and leaked. WOW. Yes the frost must have got into the tins expanded and popped the cans.
So what could the frost / ice do to 7/8 ptrs of water if left.?????
I used to leave water in toilet tank, since I have seen the tins this with my own eyes. I will never leave any liquids in van over winter now.
Just my two penneth.
I also never leave liquids in the caravan over winter but it would never have crossed my mind about liquids in a tin. Worth mentioning. Thank you Kevin.
Quote: Originally posted by Paul_B on 19/2/2024
I drain mine into a bottle ready for next time, the bottle is kept in the front locker where it can't do any damage.
Even the slightest amount of water in the wrong place in winter, will freeze and do damage. This was what happened with the old Thetford CWE250 flush pumps until an extra drain hose mod was fitted. It also happened to shower/tap housings. Been there, got the T-shirt.
Dave.
------------- Never argue with an idiot, they will drag you down to their level and beat you on experience.
Mark Twain.
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Topic: Emptying flush tank
via mobile 18/2/2024 at 7:58pm
