Cleaning out caravan watwer tank

KenG · Member

Cleaning out caravan watwer tank

Tony Bev · Guru

Hi KenG

Welcome to the forum

I am led to believe, that there are potable water tank cleaning agents, in the caravan/camping shops

I am a part time traveller, and my motorhome is parked up for weeks/months on end

I usually leave whatever water is in the tank, when I park up, then empty and refill with fresh water, the day before I start travelling

Also, I do not actually drink, the potable water from the water tank, except when I use it to make a cuppa
I use bottled water for drinking, just as an assurance, that I will not get any tummy upsets, while on the road

jade46 · Senior Member

Believe it or not 2litres of red cordial in the tank go for a drive and then drain it. Jayco Brisbane told me this and it works fine. I cannot explain but I figured it was worth a try and better then chlorine in a plastic tank

Possum3 · Guru

Ken, I use chlorine beach to sterilize tank, drain tank wash out with hose and like Jade46 put Cordial (1 X cup Cottees Lime) to neutralise any "taste" in tank. I believe you can also buy (hate that word), sterilizer wherever home brew supplies are sold.

outlaw40 · Guru

Liquid pool chlorine if your worried about your tanks ( its in the water that comes out of the taps in town ) but normally just fill the tanks when you get home and all will be good . if the van is idle for a long period of time then just drop the water and refill with fresh before you go away , i just use the water in the tanks to water the garden then refill .

outlaw40 · Guru

section 10-4 of this document covers using chlorine for disinfecting water www.health.nsw.gov.au/environment/water/Publications/private-water-supply-guidelines.pdf
obviously these quantities are for household size tanks so will need to be scaled down . have been personally using this approach for my household tanks (30,000 Gallons ) for over 30 years and i aint dead yet .

Radar · Guru

outlaw40 wrote:
Liquid pool chlorine if your worried about your tanks ( its in the water that comes out of the taps in town ) but normally just fill the tanks when you get home and all will be good . if the van is idle for a long period of time then just drop the water and refill with fresh before you go away , i just use the water in the tanks to water the garden then refill .

Like outlaw40, I drain my tanks when we get home on to the garden, fill them back to store the caravan, like this time as the caravan been sitting now since mid March I will drain them and refill with fresh water as we will not be going anywhere before July.

Bacteria grows in the tanks where there is air space, some say empty right out, others say completely full.

I have one empty tank and two full tanks. Third tank I leave empty as we may not need it and when I do, we run about 10 or so litres of water though it before closing the valve and filling.

We fill our tanks using a in line silver/carbon filter about $110 from caravan shops gets rid of most nasty things.

FMC · Veteran Member

Hydrogen peroxide is very good for cleaning the water tank, available at chemists, fill tank and add the required dose, I think it is on the bottle, fill with water and let sit for 24 hours, drain and flush.

oldbloke · Guru

Dose with in scented domestic.

Mike Harding · Guru

Go to a supermarket and look at their home brand bleach, if it contains *only* sodium hypochlorite and sodium hydroxide buy it and mix 45ml of into the 140lt tank as you fill it, leave for a day or two then flush and refill the tank with fresh water. NB. 45ml is not much *do not* significantly exceed this figure. If you intend to drink the water you are chlorinating then reduce the dose to 15ml per 140lt tank.

If you cannot find the above bleach go to the baby section and buy Milton instead - use 250ml for tank cleaning or 70ml if purifying for drinking.

Sodium hypochlorite will kill all viruses and bacteria with the possible exception of the protozoas and is the method recommended by the WHO for cleaning unsafe water.

Edit: Correction of the quantities for Milton - messed up my mental arithmetic.

-- Edited by Mike Harding on Monday 8th of June 2020 11:14:12 AM

inthegloaming · Member

The saying is the water tank should be absolutely empty or absolutely full when in storage. When you fill the tank from a town reticulated supply that has been treated and filtered there is always a tad of chlorine in that and this keeps the tank free from most bacteria. I always flush and refill before a trip. The cordial trick works because most harmful bacteria are destroyed by the strong sugar concentration. Adding a splash of chlorine to the full tank is an extra protection. Not a good idea to fill your camper water tank with tank water unless you add chlorine. I also use a food grade hose (blue colour) to avoid the contamination from PVC over time.

StewG · Senior Member

outlaw40 wrote:
section 10-4 of this document covers using chlorine for disinfecting water www.health.nsw.gov.au/environment/water/Publications/private-water-supply-guidelines.pdf
obviously these quantities are for household size tanks so will need to be scaled down . have been personally using this approach for my household tanks (30,000 Gallons ) for over 30 years and i aint dead yet .

Thanks, Outlaw40, for the link. Based on my reading of the NSW Health guide, My two 90 litre tanks need only 11 millilitres of White King bleach each to kill the bugs. That is so easy...

Someone please let me know if I've got it wrong.

Mike Harding · Guru

StewG wrote:
Based on my reading of the NSW Health guide, My two 90 litre tanks need only 11 millilitres of White King bleach each to kill the bugs.

I'd say that's a little low. White King is 4% chlorine so your 11ml equates to 44ml at 1%.

My research indicates that 0.5ml of 1% chlorine will purify water so I'd suggest 100ml of 1% bleach (or 25ml White King) for your 2 x 90L tanks - call it 200L.

Also *double check* White King does not have other additives - see my post above.

If using a bleach (as opposed to Milton) I find it easier to water it down to 1% chlorine solution before use, it's easier to be more accurate with measurements then. Additionally it's worth buying a few syringes from E-bay for more accurate measurement.

If I'm using (say) Murray River water just for washing then I double the above numbers - no way would I drink Murray water!

Edit: Sorry, just noticed you said 11ml for "each" tank. Yep, I'd say that's about right. Don't overdo the bleach or you *will* hate the taste.

-- Edited by Mike Harding on Tuesday 9th of June 2020 02:24:08 PM

StewG · Senior Member

Mike Harding wrote:
Sorry, just noticed you said 11ml for "each" tank. Yep, I'd say that's about right. Don't overdo the bleach or you *will* hate the taste.

-- Edited by Mike Harding on Tuesday 9th of June 2020 02:24:08 PM

Thanks for the confirmation, Mike, I said each tank because they have separate inlets. NSW Health seem to be fairly adamant that the concentration of 5mg/litre of free chlorine must not be exceeded. Whether that is just taste, corrosion or we would be poisoned, I don't know, but it is worth complying.

My plan, because the tanks are currently full and have been for many months, is to carefully dose the tanks, wait a week or six - until we are allowed to set off interstate - then empty and refill. The cordial treat might also be implemented, although we generally drink bottled (10 litre casks) water when travelling and only use the tank water for washing. If I was really keen (I'm not), I would get a testing kit and monitor the chlorine in the tanks to maintain potable water conditions.