Not sure it's a stain.. but it won't brush

Pool: In ground, gunite, white plaster, salt system.

I've had a 'sand' problem ever since the pool's first year, about 3 seasons ago.
A brown gritty substance collects on the steps and the outs of the pool. Usually I can brush it off, but it always comes back the next day.

Well, not it's not brushing off as easy as it used to. I have what looks like a brown stain on the plaster on the steps and the outs (any flat surface the polaris can't get to).

I rubbed a lemon on it for a few minutes, I assume it technique is supposed to be similar to placing a Vitamin C tablet on the stain, but it didn't change the stain at all.

I don't think it's algea as it's not slippery.. it's gritty.

What would be a good technique for trying to get this off the plaster?

Not getting alot of bites here..

I've seen stainless steel brushes... It might help get the stuff off the plaster.. but would it damage the plaster?

They do make some brushes that are 50/50 SS and polyester. You can also get stones that will scrub some of the top layer off, but be careful not to make the step too rough, takes good bit of time and pressure to screw it up, you will know it if you just scrub and check scrub and check.

This brush did not work for my stains, what I did was pour some Muriatic Acid out just over the stains, and the acid burned the top layer of the plaster off.

Just in case you are not familiar with working with Acid, you must wear goggles/sunglasses and rubber gloves help if you are not found of the burn of acid on bare skin.

We had some persistent stains and I used a 1.5" PVC pipe covering the stain, poured a little acid in the pipe and presto! It burned the stains right out, just a FYI only takes like 30-60 seconds to burn off the top layer of plaster. Add a little wait and check, if that does not work add a little more. For the steps you can pour straight on the steps, takes a little more Acid but will work well. I have done this 3-4 times when the kids leave something metallic in the pool when I am not home and it works like a charm.

Burning off layers of plaster does not sound like a good idea....

Well its not unless you have stains vs dirt on the surface.. Stains penetrate the substrate, therefore to remove them the only way is to remove the substrate. To remove 1/32 or 1/8 of an inch is not noticeable. My plaster is a minimum of 3/4 inch thick and in most places 1" + so the 1/8 removal is nothing. This was per the plaster company. They also do an acid wash on start up with my product (Diamond Brite) I have seen them do the acid trick on several pools. The amount of time you leave the acid active (concentrated in the pipe) is the key. I also used Acid on my plaster pool and coping years ago to remove rust stains, worked fine.

Try the brush first, if it works great, if it is stubborn dirt it may work. If it is a stain it will probably not work. You are doing the same thing with the brush, rock or acid. The speed at which you remove the substrate is the difference. You can always hire a company to do the process if you are uncomfortable. It would sure be easy to pour a little acid on the step first to see the results.

I'm just gonna put some thoughts here to see if someone else can't complete them.

I've been trying to figure this one out since it started last week.
1) We've got 'deposits/ stains' that tend to be where the water is shallower and near returns.
2) Ascorbic acid (the lemon) doesn't seem to have an effect.
3) Brushing seems to work, if caught eary enough (and the pool cleaner keeps it away, in the areas it can get to)
4) The substance in ? is brownish and gritty (my initial thought on this is calcium- but w/o it being universal to the pool, that doesn't seem right)
5) Would recommend solid chlorine, pucks or a satchel of dyr chlorine, to see if it helps, directly on a portion of the stain (Mike, you 'tested' for metals w/ the lemon, next test is for organics w/ concentrated cl on a spot)


Is there something that the return water might do to increase the precipitation of calcium?? (I can't think of anything that the freshly 'energised in the cell' water would have that could cause this)

When caught early enough, either by brushing or the passing of the cleaner, it doesn't take hold.

Thin coat of plaster, which is bleeding through??

Some sort of bypass through the filter (i'm thinking it's not sand, cause sand will just brush away, perhaps some finer organic which will pass through the sand and concentrate in the return areas - again, try the puck or cal-hypo) - or even an 'infection' of the filter itself.

That's about it form me on this.
(BTW-Big_D gave a great! response to the light ? earlier today (saved me a post by mentioning the plastic wheel in the SAM lights, and had nice input as to the lumens :D ))

AS I said, I don't know what it is, but perhaps something I've posted will 'trigger' a response from someone else.
Mike, I hope this turnes out as well as the 'CPB' question!!! :)

Thanks everyone.

Now that I've got some salt in the pool, and the SWG is making chlorine.. I'm seeing less of the buildup.

The concentrated CL on the affected area seems like the next step.

While it doesn't feel organic (I expect organic to feel slippery, not gritty, but I may be wrong about that) the fact that now that I have CL the stain is less, seems to point in that direction.

Based on your information you probably have some type of algae which is probably not in the substrate yet at least. Good for you:) and I bet you are right it is more of a chemical maintenance issue. I also agree you can add some regular old bleach and clear up most of those. My old pool would get blooms in the summer since the circulation was poor. Back then I did not know better and I would buy that expensive shock to kill it.

On the new pool I also have a SWG but I will dump in a gallon on occasion to make sure those bad organisms are in check. Also living here in Texas that summer heat is rough on Chlorine and pool use is high so it is too cheap not to stay ahead of the game.:o