Experiment removing brown toilet bowl stains with various acids

[Danny D.]

In another thread, it was determined that porcelain toilet bowls were impervious to commonly available acids such as phosphoric (Naval Jelly) & hydrochloric (pool muriatic acid).

So, I'll run an experiment to see which will remove the brown stains best without destroying the porcelain or tile.

Here is a picture of the brown toilet bowl stains, after scrubbing and household bleach - but before the first treatment:

Here are the next three planned treatments:

1. Pool bleach (12%)
2. Pool acid (28%)
3. Naval jelly

Let me know if you have any suggestions before I conduct the experiment.

[notbob]

I'm definitely paying attention.

nb

[Danny D.]

The most dangerous is the pool acid, so, I'll do that last.

Here's what I just did:

1. I shut the water supply off and flushed the toilet
2. I plunged & cupped & toweled out the remaining water
3. As a control, I blocked half the toilet with a bath towel
4. Naval Jelly (because it's sticky) went on first

This is my sister's kid's bathroom, so, while I was there, I decided to apply the excess naval jelly to the yucky sink:

I'll wait a half hour - and then wash it off, and report back.

PS: How her kids make 'that' much mess of a sink just brushing their teeth is beyond me!

[Danny D.]

Regarding the blackened bathroom sink, I left the phosphoric acid on for an hour and then, with the drain open, I opened the faucet.

Almost no water went down the drain. Huh?

Having never used the sink myself, I realized for the first time the sink had been almost totally clogged, all along, so I plunged it and black crud started bubbling up from the pipes below:

Soon, water was flowing again, such that I could see that the naval jelly worked, for the most part, to remove the black stuff and it does not seem to have damaged the nickel plated brass:

Here is what it looks like, without any scrubbing, but with just a wipedown with a wet towel (my sister was mad at me for ruining one of her hand towels, but I am at her house and my bath towel was already full of chemicals from the toilet bowl experiment):

Now, it's time to flush the toilet of the phosphoric acid ...

[Danny D.]

In retrospect, I agree.

1. I left the naval jelly on the toilet bowl for an hour:

1. The towel maintained the right side as an experimental control:

2. The results, after only flushing (no scrubbing), were not stellar:

With my fingernail, I scraped along the area cleaned by the phosphoric acid, and it felt rough, with pieces of loosened deposits flaking off, so, perhaps with more time, the naval jelly "might" have worked; but it's time to move on to the pièce de résistance, which is the 28% hydrochloric acid & baking soda experiment.

I'm reading up on Oren's suggested reference now & will report back:

[Danny D.]

The water out here is high in calcium (something like

15 ppm or so, IIRC) but there is no appreciable iron, as you have already inferred.

So, I agree with you, since in prior experiments on tools, we've determined that the phosphoric acid turns rusty tools black in just a few minutes.

That didn't happen here - hence - I would agree with you. That brown stuff isn't rust.

I'm not sure 'what' it is - so I'll leave it at "cooties" for now (but don't tell my sister that 'cuz I said it was rust).

Meanwhile ... I'm preparing the toilet bowl as I had not realized I'll be flushing a gallon of HCl into the TOP of the toilet bowl (I thought I was going to put it directly in the bowl) ... so there's a bit more preparation necessary.

Will report back as my sister is driving me crazy, looking over my shoulder all the time. She keeps asking if I know what I'm doing and why I have to be on the computer all the time if everything is really under control ...

[IGot2P]

Stain 1, naval jelly 0

[Danny D.]

Oh, it fizzled allriht! :)

I gathered the materials listed in Oren's instructions:

I was going to use a protective facemask ... but they suck:

I took off the cover of the toilet bowl tank:

I wrapped the bowl with plastic wrap to keep fumes inside:

The rubber tube on the funnel turned out to be useless:

And, I started pouring 28% muriatic acid into the 'thing':

As Oren mentioned, it bubbled and hissed like a caged tiger:

And bubbles were even forming in the toilet bowl tank itself:

The vertical tube itself encrusted with white deposits bubbled:

After about 1/4 gallon of 28% HCl, I baggied the vertical tube:

The whole thing is bubbling away as we type:

As I sit down to a belated dinner with my kid sister & progeny:

(I will report back in about an hour - for better or worse.)

[Danny D.]

Ooops. I must have missed that step in the instructions. Can you actually empty the bowl without emptying the tank?

Anyway, the deed is done.

After an hour of hissing and bubbling, I sprinkled the antidote:

Of course, that initiated a new round of hissing and bubbling:

After flushing a few times, I poured in the 12% pool bleach:

Now the bowl is "almost" clean of the brown "cooties":

My sister wants to know why I still left a little bit ... Rust 1, naval jelly 0 Rust 1, muriatic acid 10

[Danny D.]

A couple of minor questions ...

1. How much baking soda counteracts a 1/4 gallon of HCl?

1. What was that floating mat of greenish stuff in the end?

2. Can you really empty the bowl WITHOUT emptying the tank?

1. Why do the respirator masks have such crappy rubber bands?

[notbob]

Gotta make a choice on that one, as lowering the water level too far opens the water baffle (seal).....

.....thereby exposing the fruity aromas of yer sewar or cesspool to yer delicate snozola. Yum!

Yes it does, and many thanks go to Danny for that intrepid toilet tutorial. ;)

My only question is: How did the porcelain fare? Any deterioration of the glassy smooth surface?

nb

[dadiOH]

From what? The hydrochloric (muriatic) acid? Not a chance.

The glassy smooth surface is just that: glass. Acid - except hydrofloric - is stored in glass containers (or, nowadays, plastic ones). One could also use sulphuric (battery) acid. Or nitric. You could even mix up some aqua regia (hydrochloric + nitric) and be good as gold. Except if the commode was gold plated.

[dadiOH]

Tell your sister to get a stainless steel mesh "stopper" for the sink (HD/Lowes/etc) and to make her offspring empty it from time to time.

Alternatively, suggest that she use some Drano once in a while. Drano is lye with some bits of aluminum. The lye digests organic material and also reacts strongly with the aluminum to create considerable heat and frothing (within the pipes) thereby aiding the disintegration of the organic matter.

[Danny D.]

This is good advice as the experiment was done for the acid, so there was no brushing yet ... just chemicals ... on purpose ... so that we could tell which worked best bleach --> useless for the brown stains naval jelly --> nearly useless for the brown stains pool acid --> perfect for the brown stains

Yes. But I noticed "other" toilets in her house which seem to need "the cootie treatment", so, I told her I'd come back to finish them off.

Any other ideas for experiments?

[notbob]

Good enough!

nb

[Danny D.]

Excellent diagram! I now understand, from the diagram, that I could have emptied the bowl without emptying the tank.

One question about this diagram:

Where is that dark blue path of water in 'my' toilet bowl?

[Danny D.]

I'd agree with Oren, but it's not all that easy to tell.

Certainly there were spots of smooth glaze afterward, but there were also areas of roughness.

Since there were areas of smooth glaze, I'd have to assume the porcelain was not damaged by an hour of 28% pool acid; and, I'll assume, for now, that the rougher areas were simply coated with Calcium deposits.

However, I'll take a closer look when I return to the scene of the crime.

Here, by the way, is a composite before & after montage:

[notbob]

Quite possible. That's one of the downsides of using bleach. It doesn't alway "remove" the offending stained medium, it merely whitens it. I've seen residual slime/mold turned white by bleaching action, despite the slime/mold still being present.

nb

[Danny D.]

Interestingly, the weak 4% household bleach didn't do anything visible when poured directly into the bowl initially ... but ... afterward, in the tank, the 3x stronger 12% pool bleach DID whiten the remaining strands of brown stain!

However, it might be that the pool acid somehow 'weakened' the brown stain, such that the pool chlorine could attack it - or - it could simply be that the pool chlorine was stronger than the household bleach initially used.

[Danny D.]

Good point. My mistake.

I did NOT wait 'till the baking soda stopped reacting; so the wastewater is likely a bit on the low pH side right about now...