Acid Concentration Required to Descale Black Water Pipes?

[StuM]

Originally Posted by ontherocks83

Mainesail disproved that myth in one of his articles. It didn't do anything to the build up.

How did he use the vinegar.

All I know is that it certainly worked very well for me the way I used it.

I had a completely blocked hose in the guest head. (Subsequent investigation disclosed that the low point in the hose was so constricted by scale that there was only a roughly 1/2" diameter hole left and the hole was blocked by a single "wet wipe" which my daughter or one of her friends had flushed.

I removed the hose and sat it in a large bucket with the open ends elevated and filled it with vinegar. Judicious use of a stiff piece of wire with a couple of barbs filed into the end combined with several replacements of the vinegar was enough to hook out the obstruction and soften/break up the scaling to the state where I could bang it against the dock and get all of the deposits out.

Every time I applied new vinegar it foamed initially and when I emptied it out scaling in the visible part of the hose was greatly reduced.

[ontherocks83]

Originally Posted by StuM

How did he use the vinegar.

All I know is that it certainly worked very well for me the way I used it.

I had a completely blocked hose in the guest head. (Subsequent investigation disclosed that the low point in the hose was so constricted by scale that there was only a roughly 1/2" diameter hole left and the hole was blocked by a single "wet wipe" which my daughter or one of her friends had flushed.

I removed the hose and sat it in a large bucket with the open ends elevated and filled it with vinegar. Judicious use of a stiff piece of wire with a couple of barbs filed into the end combined with several replacements of the vinegar was enough to hook out the obstruction and soften/break up the scaling to the state where I could bang it against the dock and get all of the deposits out.

Every time I applied new vinegar it foamed initially and when I emptied it out scaling in the visible part of the hose was greatly reduced.

Read the article it's not super long and is informative. I would "assume" that most of the benefit was from your stiff wire brush opposed to the vinegar itself, but like I said I'm just assuming not doing an actual test.

[Dave Lochner]

It's all about the chemistry.

The problem with vinegar is that the concentration of acetic acid in vinegar is very low, about 4%, if I recall correctly. With that level of acidity (ph is a different issue) it takes a long time and a lot of vinegar to clean out a large build up.

Small amounts of scale might be cleaned with vinegar and as a preventative measure may help and does no harm.

Muriatic acid (HydroChloric Acid) sold in hardware stores is about 30% acid and is pretty strong. Out of the bottle it will blast through scale in minutes. Diluting it to 15% might be prudent. If I remember the chemistry correctly, it breaks down into to calcium chloride (a salt) and carbon dioxide and some other salts.

Phosphoric acid will also work. Sew Clean is product sold to clean black water plumbing. The problem with phosphoric acid is that it breaks down into phosphates which is fertilizer and a chemical the US has been trying to get out of the water because it promotes algae growth.

"Agricultural" or "horticultural" vinegar is 30% acetic acid which should work better than plain old white vinegar.

[Kalinowski]

We've been using muriatic acid for years with no problem. When the pump handle starts to give a little resistance, I'll pour about a cup (never measure) directly into the bowl and pump 2-3 times to get it into the hose and let it stand for 15 minutes. Then flush. I follow with a splash of vegetable oil pumped through to lube the working parts. Never had a problem.

Be careful with pouring the acid in the water. The fumes are noxious.

[Dave22q]

From the posts I gather that acid will not damage the pipes but what about the tank. Is mureatic acid safe on plastic and aluminum tanks? I have seen that scrubbing with vinegar can remove early scale buildup in the bowl but that is very different from rushing past old build up in the pipes. That might be ok as a prophylactic but not as a built up deposit remover in my humble opinion. On an experiment with a plastic urine jar I found that soaking for over an hour in pure vinegar was worthless but I did not try scraping, just soaking. I suspect a brief exposure to a stronger acid would do no better.
As for cleaning the holding tank, it seems to me that if some acid would do it we would see a dozen high priced acid tank washes in West Marine and the like.

[Dockhead]

Originally Posted by Dave22q

From the posts I gather that acid will not damage the pipes but what about the tank. Is mureatic acid safe on plastic and aluminum tanks? . . .

Hydrochloric acid will eat up an alu holding tank so fast it will make your head spin. Don't even think about it!

But an alu holding tank? Does such a thing exist? Seems like an entirely unsuitable material for holding tanks.

[Dave Lochner]

Originally Posted by Dave22q

From the posts I gather that acid will not damage the pipes but what about the tank. Is mureatic acid safe on plastic and aluminum tanks? I have seen that scrubbing with vinegar can remove early scale buildup in the bowl but that is very different from rushing past old build up in the pipes. That might be ok as a prophylactic but not as a built up deposit remover in my humble opinion. On an experiment with a plastic urine jar I found that soaking for over an hour in pure vinegar was worthless but I did not try scraping, just soaking. I suspect a brief exposure to a stronger acid would do no better.
As for cleaning the holding tank, it seems to me that if some acid would do it we would see a dozen high priced acid tank washes in West Marine and the like.

I would be hesitant to use any acid in an aluminum tank.

Plastic tanks and fittings should not be bothered by weak solutions (under 30%). After all, vinegar and muriatic acid come in plastic jugs.

Here are some before, during, and after photos of a clogged Y valve. It took less than 5 minutes to completely clean the valve with 30% muriatic acid.

In this months Sail Magazine, Don Casey writes about cleaning a very dirty holding tank. In recent months Practical Sailor also wrote about cleaning water tanks, probably the same method would work on a holding tank.

(In the 3rd photo it appears that the y-valve was bleached, it was not. Just the difference in lighting between my basement and side yard.)

[JimsCAL]

I use oxalic acid each spring to clean my waste lines. Less aggressive than muriatic/hydrochloric but much stronger than vinegar. I also use it in the fall to clean my waterline after being hauled. Available in most hardware stores as a box of crystals for $5 or so that makes several gallons of liquid.

[peghall]

muriatic acid will not damage anything in a sanitation system. Until Raritan began marketing SewClean under their own private label brand name "C.H. Cleans Hoses," their instructions for cleaning the LectraSan called for a 12% solution of muriatic acid.

As for vinegar...all those who tested it and declared that it doesn't work only put whatever they were descaling in it and let it sit for days...not realizing that was the reason it didn't work...that vinegar loses effectiveness in an hour or so....a heavy buildup requires multiple reapplications. It does work...it's just more of a PITA to use as a cure. A cupful once a week is a lot easier and does do a great job of preventing scale buildup.

[reed1v]

We used white vinegar once a week followed by a cup of veggie oil, olive oil, or whatever food grade oil we had on hand. Kept heads clean and easy to work. Worked for us over many decades.

[jamhass]

Originally Posted by peghall

muriatic acid will not damage anything in a sanitation system. Until Raritan began marketing SewClean under their own private label brand name "C.H. Cleans Hoses," their instructions for cleaning the LectraSan called for a 12% solution of muriatic acid.

Peggy:

I've always been a bit leery of using muriatic acid with my stainless steel holding tank, as it is HCl, and SS + Cl often makes for unhappy result. Since you have more experience than the rest of us put together ... any comments on HCl + SS?

[Dockhead]

Originally Posted by jamhass

Peggy:

I've always been a bit leery of using muriatic acid with my stainless steel holding tank, as it is HCl, and SS + Cl often makes for unhappy result. Since you have more experience than the rest of us put together ... any comments on HCl + SS?

"The common stainless steel types, 304 and 316 should be considered non-resistant to hydrochloric acid at any concentration and temperature.
Higher grades of stainless steel can have limited resistance, up to around 3% maximum at ambient temperatures, but may suffer local attack, mainly as crevice and pitting corrosion, even at such low concentrations.
The steep curves for 316 and the higher alloyed grades on the iso-corrosion diagram illustrate their very limited resistance."

Article: Selection of stainless steels for handling hydrochloric acid (HCl)


But all this begs the question of whether stainless steel is at all a suitable material for a holding tank. I think it's really not.


Another begged question:

Would it be better to be using something like citric acid? It's not all that expensive.