Hydrochloric Acid 36.2%

One of the problems of using acid in heads outlet pipe is that the scale can come off in lumps or flakes and block the seacock.
 
As ever with this type of treatment, prevention is better than cure. Regular dosing with HCl is far more effective than trying to remove a serious accumulation of salts. As has been pointed out, it takes a lot of acid to remove a relatively small amount of deposit. Even though I do dose from time to time I still needed to remove the hose and bang it last year and a surprisingly large amount of unpleasant stuff came out. Also of course, it is very difficult to fill an upward looped hose.
 
PlanB said:
One of the problems of using acid in heads outlet pipe is that the scale can come off in lumps or flakes and block the seacock.
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That isn't the case with this stuff that I'm using!
It goes to work and totally desolves the calcium that it comes into contact with.
Also, I am working on the section of pipe from the anti syphon valve down to the heads, not the section from the anti syphon valve down to the seacock.
 
thalassa said:
Where would the CO2 come from? At that concentration, the fumes are indeed HCL gas. I've seen two patients in Intensive Care because they had used the stuff in a badly vented room. The gas solves in the lung lining, causing pulmonera edema ('water in the lung')
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It would come from the reaction with the calcium carbonate that the OP is attempting to remove. And yes, HCl gas would be a problem if there was a large surface area, but the OP is using it in the constraints of a toilet system, where there would be a limited free surface compared with the volume of acid required. He suggests introducing it at the anti-syphon loop, as well, so there would be very limited free surface. I think I suggested that ventilation was a good thing; if I didn't I should have! I'd also dilute the acid before use; as you say, 36% HCl would require care in its handling, and that strength is not necessary for removing lime-scale.

You make a good point that HCl gas is dangerous stuff!
 
There are a number of "plastic" types of polymer that are indeed affected by stray HCl gas (fume).
For example most standard cable ties are no use in a galvanizing plant which has low level HCl floating about. They just disintegrate.
I'd take extra care to avoid any HCl fume in a cabin full of devices and items made with plastics.
 
Fumes are a problem with concentrated acid, 36%

For domestic use, branded Tile Cleaners and toilet cleaners use concentrations below 30%, often referred to as moderately concentrated acid. See safety sheet:
http://www.cleapss.org.uk/attachments/article/0/SSS20.pdf?Secondary/Science/Student+Safety+Sheets/

Your stomach produces 0.5% solution.

Generally, if you dilute concentrated with about twice as much water, you have a safe acid to handle in almost any conditions, with no fume worries and very little chance of damaging any seals or fittings.

Many stainless steels corrode in dilute hydrochloric acid, and should not be exposed to it for any period of time.
 
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MM5AHO said:
There are a number of "plastic" types of polymer that are indeed affected by stray HCl gas (fume).
For example most standard cable ties are no use in a galvanizing plant which has low level HCl floating about. They just disintegrate.
I'd take extra care to avoid any HCl fume in a cabin full of devices and items made with plastics.
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Thats because they are nylon ITYWF.

The majority of common plastics should be unaffected
 
AntarcticPilot said:
It would come from the reaction with the calcium carbonate that the OP is attempting to remove. And yes, HCl gas would be a problem if there was a large surface area, but the OP is using it in the constraints of a toilet system, where there would be a limited free surface compared with the volume of acid required. He suggests introducing it at the anti-syphon loop, as well, so there would be very limited free surface. I think I suggested that ventilation was a good thing; if I didn't I should have! I'd also dilute the acid before use; as you say, 36% HCl would require care in its handling, and that strength is not necessary for removing lime-scale.

You make a good point that HCl gas is dangerous stuff!
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Yes, sorry, I thought you were referring to the bottle of concentrated acid, not the reaction. I was aware of the chemistry involved in that. My neighbour, an avid DIY fan, wanted to varnish his oak floor. One of the most durable products is two-pack polyurethane lacquer. One part is hardener/accelerator, and was in that case concentrated HCL, about 10-20%. It was winter, and he kept the windows closed, otherwise the hardening process would take too long or it wouldn't fully cure. We had an interesting chat after he came out of Intensive Care four days later. I believe the product is now 'reserved for professionals'.
 
Units

There seems to be a lot of confusion over units. Concentrated hydrochloric acid is 36% approx. That is as strong as it gets for normal purposes.

A 30% solution of that is 300 ml of concentrated per litre of water ie about 12% hydrochloric acid. Toilet cleaner is generally about 10% acid so 100 ml of concentrated acid per litre (3.6% acid).

The fumes are very nasty indeed when mixing the concentrated acid with water. I make up large quantities of 10% acid daily in a fume cupboard, and just washing the empty bottles produces a lot of choking gas.

I would dilute the concentrate by 1:10 for descaling, and with great care. I wouldn't want to keep a bottle of the concentrated acid around anyway. And don't forget to put fresh water in the loo not salt, or some of the acid will be used up by the sea water.
 
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