Fresh / grey water tank descaling

A bit depends on whether you want to remove calcium deposits or iron stains. Calcium is usually there as calcium carbonate and iron as a form of hydrated iron oxide (similar to ochre). You need something to dissolve them, usually an acid, then have something to prevent them reprecipitating or forming a coating that prevents the cleaner from acting on the remaining scale. A strong acid like hydrochloric would work but would not be compatible with metal fittings and perhaps seals and also needs careful handling using personal protective equipment. Acetic acid (vinegar) is a weak acid and will work for calcium carbonate but not so well for iron. I had a look at the msds for CLR and it uses a mixture of weak organic acids and complexing agents, presumably the formulation works as the name stands for calcium/lime/rust. Once you add in soap scum it gets a bit more complicated. Perhaps if you sequentially tried CLR->water->vinegar->water->bicarb soda in water (to neutralise residual acid), then 3x rinse with water. This should rinse out the residue of the cleaners no problem, the issue is while none of these will affect plastic, especially in short term exposure, metal bits could quite easily be adversely affected so if you have pumps, hand pumps etc with metal then they would need to be disconnected prior to cleaning to be safe. Another question is if it iron staining you are worried about, do you really need to get rid of it, as long as there isn't so much that it's clogged things up, it's not going anywhere? The solubility of these iron oxides is very small that's why it coats things in the first place. Good luck

you'll never have looked in ya jug at home then.

Yes we had some slight residue in our vans jug and kettle and citric acid removed it. However after seeing the huge mineral build up on the fresh water tap in a NT caravan park, I was alarmed. Needless to say we did not connect water from this tap into the van. I found all water though, especially from the various bores has mineral content to some degree.

The mineral content will be mostly iron so little to be concerned with as far as health ..... flavour will be more of a problem than anything.

cheers

Don't think you've got too much to worry about, Hooks. As Hoyks said, it would only be a problem if the tanks were allowed to dry out repeatedly. Engine cooling systems are one example where there is constant heating and cooling, and build-up of scale from heat.

Have spent a lot of time around bores, and it's only the really salty, or highly mineralised ones that have rapid scale or residue build-up. Have seen a 40mm pipe choked up with scale, with only a 12mm hole through the centre allowing water flow. This was on a single cylinder stationary engine, that used a 44 gal drum as a cooling reservoir.

That tap you mentioned was probably weeping slightly, and the water was constantly evaporating, causing the scale you noticed. Any bore is worth a "taste test"....if it's not tasty immediately, then maybe give it a miss. Probably the worst it can do is flush the system out! :-)

Bob