Converting a SS Grey Water tank to Drinking

I suggest a biological treatment first, left sit for several days to ensure all the food stuff is degraded. A serious chlorine treatment and lots of flushing should then get things back to safe drinking standard.

Iza

Frank,

Grey water leaves behind a lot of foamy residue, that would stick like you know what to a blanket. If you could get to it, it could be cleaned quite easily, but as that's not the case here, I'd suggest a diluted acid, to etch the interior, then followed by some sanitising, and deodorising. And as said above, lots of flushing.

But thanks all the same, I'll pass on that offer of a cup of tea, coffee, or a glass of water.

Bob.

Hi Frank,

I have just gone through a thorough cleaning of my camper 120l water tank.
I have been attempting to clean it on numerous occasions.
My problem was a persistent brown water contaminant that I just couldn't flush out in the normal way. I believe the tank may have been filled at some stage with muddy river water.

My final solution was to drop the tank so I could invert it in all directions.
I discovered this tank also had internal baffles.

Following a vigorous flush, I added a couple of cups full of household bleach, filled the tank fully and left it to stand overnight. (eg about 12 hours). The tank was left standing on one end, with the filler inlet and the drain and breather outlets uppermost.

I emptied the tank, filled it with clean water and emptied it again.

I again filled the tank, this time adding 1/2 packet of baking (bi-carb) soda to the water and again filled it. This was to neutralise the bleach taste.

Emptied it again and filled and flushed it again before re-installing it into the camper.
Filled it a final time and the water is now running clear and tastes normal.

I think the main problem with camper/caravan water tanks is the inability to completely flush it via the normal drain outlet, which is both small and not necessarily at the absolute bottom of the tank.
By being able to invert the tank after its removal, I could empty it completely via the larger filler inlet which was now at the absolute bottom. This allowed all deposits to be flushed out as much as the bleach could remove. The tank could be manually shaken about as the water (and therefore the weight) was reduced.

I would not recommend anything else but normal household bleach to use, after I did some considerable research on the web.
I used White King Regular bleach and two cups was a little more than was recommended for the 120 litre tank, but still within an acceptable limit.
Anything stronger could affect the stainless steel surface and seams and welds, etc.

I think the task is worth the effort, especially if, like my case, you can remove the tank.
It is not a simple job, but reassembly was assisted in my case by the use of a trolley jack to help locate the tank back into its recessed compartment.

Having only completed the job the weekend before last, I have yet to run the taps to check water quality for a final time but I am confident that I have been able to fully recondition the tank back to an acceptable water quality standard.

A multi stage atack is probably best in conjuction with a road blessed with a lot of traffic calming.

I recon napi san..lots of it.... would be a good starter.......its pretty usefull and inocuous....... and is designed to shift greasy slimy stuff.

a couple of slow laps over a series of speed bumps.....preferably diagonally.

Citric acid is a pretty good cleaner and is used for everything from cleaning roofs to sterelising medical equipment.....one of its big advantages is it rinses out cleanly.

cheers

I think you are on the right track.
With grey water, there might be a lot of body fats stuck to the insides of the tank.
I'd start with some caustic soda to eat out the fatty sludge. Then rinse and go with bleach and rinse with water and a little dilute acid to take out any left over caustic soda.
You'll either be left with a clean tank or no tank!
Whitworths sells a nice Stainless waterproof hatch that you might be able to hole saw into place. That might give you better access.
Stainess deck port
You might have to put a couple of blobs of Sikafles on it to stop it unscrewing. I'll be using them in my tanks.

Frank - Use only bleach and citric acid for cleaning (separately, of course), and only sodium bicarbonate for neutralising.
Tank removal is the only sure way of getting all the crap out.
If it's possible, after putting a few litres of your cleaner in the tank, strap it or clamp it firmly to a rotating item - a tractor wheel, a concrete mixer, or something similar.
This is the method we use to clean rusty fuel tanks when doing restoration work. It works very well.

Cheers, Ron.

Thanks everyone for your replies, I think I have a handle on it now.

If I were to use bleach, caustic soda solution, citric acid and bicarb soda as a neutraliser, what do you think would be the best order. (I understand the need to neutralise between caustic soda and the acid and vice versa)

Wish I had a tractor (Thanks for the idea, Ron), but not much use for one of those in suburbia. A hired concrete mixer will have to do.

Cheers

Try one of the citrus cleaners ie. Citra clean that will strip any fat or grease from the tank
We use it at 3 times the label rate as a grease remover works a treat
Kev