Hydrochloric acid to remove uric crystal buildup?

[AntarcticPilot]

?? I think that should read 73 g of HCL
Also every 100g CaCO₃ will give rise to approx 25 litres of CO₂

Quite right - I forgot the 2! And I did do the atomic weight of Chlorine from ancient memory. So where I said 1 litre of acid, it should be 2. And, of course, that's highly concentrated hydrochloric acid, which is not exactly over the counter stuff.

 

[starfire]

The hydrochloric acid sold in supermarkets in Greece and Spain is about 6% HCl.

Useful stuff for regular maintenance is cleaning vinegar, about 80c a litre in Spain

 

[Mistroma]

?? I think that should read 73 g of HCL
Also every 100g CaCO₃ will give rise to approx 25 litres of CO₂

I did some very rough calcs. many years ago and seem to remember that the 38mm ID pipe holds a little over 1 litre per metre length. I assumed that hydrated calcium carbonate wouldn't have a density higher than 3, meaning a completely choked pipe would hold about 3kg of crystals. I seem to remember that I'd need about 40 litres of ~6% agua fuerte to neutralise that amount.

It was quite a few years ago and I know that the actual figure would probably be a bit lower for several reasons. Of course it would be pointless with a completely choked pipe, just a bit of mental arithmetic to satisfy my curiosity. I think even a 5-6mm thick lining on the pipe would need about 10 litres of agua fuerte. I bet many people try to clear a badly choked system with about 500mls and worry that they are using too much.

I rely on copious flushing plus some agua fuerte every 6 weeks to remove any tiny deposits. I saw no sign of deposit after about 10 years use when I last checked the hose. I'm lucky to have 2 heads and only pee in the forward head to allow minimal flushes in the aft. head with its holding tank. I have a different cleaning regime for the aft head and tank. Zero build up there as well. I think it pays to give some thought to these matters instead of leaving it until blocked.

 

[Mistroma]

Useful stuff for regular maintenance is cleaning vinegar, about 80c a litre in Spain

I suspect that it will also be about 6% and is also a weak acid. Hydrochloric acid is a strong acid and will react more rapidly. I also keep vinegar and use it sometimes if short of agua fuerte and it also has other uses.

I tend to keep a small collection of acids, alkalis and misc. bits on board.

Agua Fuerte, vinegar, caustic soda, sodium bicarbonate, sodium meta-bisulphite, bleach, citric acid, malic acid, oxalic acid and so on.