Hydrochloric acid to remove uric crystal buildup?

Tim Good

Tim Good

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When our toilets get a layer of uric buildup in the actual bowl, I find hydrochloric acid is one of the only things that will dissolve it in seconds. However, I've very quick to rinse it all through as I;m paranoid about having acid in the pipes which might weaken or hole them.

Bascially am I being paranoid? Could I actually put a reasonable amount of hydrocholric down the loo in an effort to remove uric scalling in the pipes? Over the years the ease of pumping has slowly got more difficult and I suspect the pip diameter is getting smaller as the build up grows. I'm careful to flush well and leave it full of fresh water when wintered but still I think there is a gradual build up. I suspect the pipes are original 25 years old.
 
I've found brick cleaner, basically HCl, to be very effective. I don't think it has any adverse effect on plastic pipework etc but I wouldn't leave it for many hours in contact with metal fittings, although bronze or brass should be OK with it. This just precautionary.
An alternative could be to remove the pipes and beat them with a piece of wood.
 
earlybird said:
I've found brick cleaner, basically HCl, to be very effective. I don't think it has any adverse effect on plastic pipework etc but I wouldn't leave it for many hours in contact with metal fittings, although bronze or brass should be OK with it. This just precautionary.
An alternative could be to remove the pipes and beat them with a piece of wood.
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Yeah is the removal that would be a big job and I’d replace with new if I went that effort. One of our heads has a fairly short run. The aft cabin has a strange set of pipe work via a black tank that can be isolated so the pipes are long and wind behind cabinets.
 
northcave said:
When our toilets get a layer of uric buildup in the actual bowl, I find hydrochloric acid is one of the only things that will dissolve it in seconds. However, I've very quick to rinse it all through as I;m paranoid about having acid in the pipes which might weaken or hole them.
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What makes you think it is uric acid?
I think you will find that is probably a carbonate deposit

Bacteria in the water and solid waste break down nitrogen compounds in urine producing ammonia
The ammonia raises the pH of the water causing bicarbonates in the water to be converted to carbonates and deposited as insoluble calcium carbonate and possibly magnesium carbonate.

Any dilute acid will dissolve the carbonate. A strong acid like hydrochloric acid will do so more quickly than a weak acid.

Dilute hydrochloric acid will not harm butyl rubber lined sanitation hose

More thorough flushing of the toilet to removes urine from the pipework will reduce the degree of carbonate deposition
 
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VicS said:
More thorough flushing of the toilet to removes urine from the pipework will reduce the degree of carbonate deposition
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Correct
But it will not remove that which is already there & that is the OP's issue.

So the question remains- How long should one leave acid in the pipe & how much acid.
When I removed my tank & pipes last I found that there was a significant build up in the SS bend of the holding tank where the pipe entered the tank.That was in addition to areas along the pipe. With 2.8 metres of pipe that would be a lot of acid & then once disolved into a paste, it still has to be pumped free & not such that it just causes a big muddy blockage further along the pipe.

Really the best answer is- as Vic says, is regular fresh water cleaning AFTER the pipes have been replacedn or properly cleaned. Old pipes get very stiff & it is often better for replacement purposes to get new ones. I had to cut my last ones into sections to remove them. I now have non wired sanitation hose that I can compress with a clamp near the areas that I know, from experience , start to clog. This helps break up pieces from the side walls.
 
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If you run a search for a member called headmistress you will see all you need to know on this subject has been discussed over and over, just flush some vinegar into the pipes when you are leaving the boat for long periods.
 
Whatever you do, don't disturb the pipes!!!

I did when fitting a new pump to the toilet - the deposits inside the pipe started to break away when I moved the pipe and then caused blockage after blockage after blockage at the sea-cock.

Eventually I ripped the pipes out in a fit of frustration and jumped up and down on them on the marina pontoon until all the deposits were gone.

Re-fitted and no problems since.
 
Having dosed my toilet, hoses and holding tank many times with hydrochloric acid, I can say that it takes a huge volume of acid to remove hard carbonate deposits. It is very difficult to fill hoses with acid sufficiently well to do the job and for the tank it is a waste of effort. Replacement of the hoses is really the only worthwhile answer, and clean the tank by scraping and pressure hosing.
 
Prevention is better than a cure. Seawater comes for free so far as I know and there is no law against generous pumping.
 
vyv_cox said:
True enough but a holding tank conflicts with this philosophy.
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There will be build-up in the holding-tank if the residue is left in for any time, but it should be possible to flush out the pipework outside, though this will depend on the set-up. In the case of my boat, the holding-tank is just a side branch of the heads outlet. It is therefore simple to shut off the tank and flush clean water through the rest, if one is prepared to accept a very small amount of waste being included.
 
You can calculate how much hydrochloric acid is required. The equation is

CaCO3 +2HCl -≥ CaCl2 + H2O +CO2

So, 41 grams of HCl will remove 100 grams of calcium carbonate. But even highly concentrated hydrochloric acid is only about 40% HCl, so roughly a litre of concentrated HCl will remove a kilogram of calcium carbonate. There are probably several kilograms of carbonate deposit in a pipe clogged up enough to notice.

The problem is twofold: first, the acid can only dissolve from the surface of the scale, and second, lumps may dislodge and cause blockages. But the point is that you need a lot of acid to clear pipework, and need to be patient.
 
AntarcticPilot said:
You can calculate how much hydrochloric acid is required. The equation is

CaCO3 +2HCl -≥ CaCl2 + H2O +CO2

So, 41 grams of HCl will remove 100 grams of calcium carbonate. But even highly concentrated hydrochloric acid is only about 40% HCl, so roughly a litre of concentrated HCl will remove a kilogram of calcium carbonate. There are probably several kilograms of carbonate deposit in a pipe clogged up enough to notice.

The problem is twofold: first, the acid can only dissolve from the surface of the scale, and second, lumps may dislodge and cause blockages. But the point is that you need a lot of acid to clear pipework, and need to be patient.
Click to expand...
The hydrochloric acid sold in supermarkets in Greece and Spain is about 6% HCl.
 
AntarcticPilot said:
You can calculate how much hydrochloric acid is required. The equation is

CaCO3 +2HCl -≥ CaCl2 + H2O +CO2

So, 41 grams of HCl will remove 100 grams of calcium carbonate. But even highly concentrated hydrochloric acid is only about 40% HCl, so roughly a litre of concentrated HCl will remove a kilogram of calcium carbonate. There are probably several kilograms of carbonate deposit in a pipe clogged up enough to notice.

The problem is twofold: first, the acid can only dissolve from the surface of the scale, and second, lumps may dislodge and cause blockages. But the point is that you need a lot of acid to clear pipework, and need to be patient.
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?? I think that should read 73 g of HCL
Also every 100g CaCO3 will give rise to approx 25 litres of CO2
 
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