Trouble Identifying Stains

[BillV]

Hi all, TFP's been great for my water, but the plaster is not looking so good. I have two different stain types that seem to be growing. One is over a wide area of the pool, and is kind of a light tan. The other is a very dark stain showing up in small spots. Any assistance in suggesting additional tests or opinions as to what to do next for treatment would be great. I have read a bunch of posts here at TFP, but not really sure which direction to go.

I've tried identification testing with trichlor pucks, hydrochloric acid poured down a pipe, and ascorbic acid. No definitive results from any of them. Maybe just a bit of a response to the AA after an hour or so, and particularly on the darker stain. I took the pic's below when I tried the AA.

This one just after I put some vitamin C tabs on the stain.

The darker stain.

A close up.

An hour later.

The dark one later.

FC 4 ppm
CC 0 ppm
pH 7.3
TA 50 ppm
CYA 30 ppm
CH 875 ppm
Borates I've added 2 boxes of borax but then decided to stop until I got the stain under control in case I needed to change a bunch of water.
Temp 65F

There was a time when I first got the pool (older pool, got it with the house) that the pH was quite high and that may have started the staining. No heater so not sure where metals might be coming from. I had a bunch of palm tree "berries" to clean out of the pool when I first was converting from a green swamp.

All I've been doing to combat this is trying to keep the pH in the low 7's in case it is calcium.

Help! Thanks!

 

[257WbyMag]

Are the spots rough to the touch? Looks an awful lot like calcium to me.

 

[BillV]

Thanks for the assessment.

I have not been in the pool since the problem really became extensive so I'm not sure. Would it be so rough that I could tell the difference using a pvc pipe?

I'm pretty sure the plaster is kind of old too. Does it typically get a little rough so it is hard to tell? Since I am new to the pool (I only swam once after I got the water clear before it got too cold) I'm not sure what "rough" really means.

If it was calcium wouldn't the "acid down a pipe" have shown dramatic results?

 

[duraleigh]

Old plaster will wear but shouldn't be rough. The acid down the pipe would have little, if any affect. It looks like calcium to me as well.

There is a thread somewhere on this forum that a member posted using a no-drain acid wash that worked well for him.

If you can clearly identify the stain as plaster [edit: I meant calcium ], you might consider what he did.

 

[BillV]

OK, I went out with a length of PVC pipe and there is clearly a difference between the open areas and the scale. The scale is much rougher. Looks like it is calcium if the acid would not have been too dramatic.

I have read the no drain acid wash threads and I may give it a try. But I have a few questions.
I don't really understand why such a procedure would work if straight acid down a pipe is not so effective.

My CH is high so would I just start redepositing afterward? Scaletec and Beautech were mentioned as being used with the no drain acid wash. Are these sequesterants?

Should I replace some water before or maybe after?

Or could I use the high acid levels as a time to add my Borax when it is time to raise the pH again?

 

[duraleigh]

I don't really understand why such a procedure would work if straight acid down a pipe is not so effective.

length of exposure time.....the acid is QUICKLY diluted down the pipe

My CH is high so would I just start redepositing afterward?

If you do not manage your water chemistry, it will. If you test and monitor your water, your problems will be over.

Should I replace some water before or maybe after?

That depends entirely on your current test results. Do you have some? If so, post those up along with the CH and pH of your fill water.

 

[BillV]

Thanks Dave, for that and all you do here. I have one of your test kits and it really helped me to understand what is going on with the pool. Per my first post the pool is:

FC 4 ppm
CC 0 ppm
pH 7.3
TA 50 ppm
CYA 30 ppm
CH 875 ppm
Borates I've added 2 boxes of borax but then decided to stop until I got the stain under control in case I needed to change a bunch of water.
Temp 65F

There was a time when I first got the pool (older pool, got it with the house) that the pH was quite high and that may have started the staining.

Our tap water is:
pH 7.4
CH 290

I've been keeping the CSI between -0.6 and 0 but the scale keeps growing. Hopefully we will continue to get rain and I can get the CH down.

What do you think?

 

[Aquatica]

is this marcite? looks like a couple pools I look after that need resurfacing. They had high CH and the plaster was old. I'm sure you will get some great advice on here. the pool is drained? Have you tried a spot acid wash on a stain? Does it come off? it should as the acid wash will strip a thin layer of top plaster to expose fresh plaster. Definitely your CH is way too high. however don't attempt an acid wash if your plaster is too old. It could damage the finish. We won't acid wash old plaster. would be best to resurface with Diamond Brite.

 

[duraleigh]

Hi, Bill,

Well, that CH number and the fact that you've had high pH in times past is a surefire recipe for calcium deposits. Trying to slowly reduce the CH is going to be slow and drawn out (ask Richard320) but it can be done. Keeping your pH down around 7.2 should halt any further deposits but the real solution is to acid wash or replaster.

Have you seen the thread on here about a no-drain acid wash? You might consider it.

 

[BillV]

Dave,

Yes, I have read Richard's various comments and a couple of the no drain acid wash threads.

I'm pretty sold at this point on trying the no drain acid wash.

I would like to get the CH down with some water replacement. Do you think I should do this before or after the acid wash? Seems that before might help the process along. But afterward all that calcium that went back into solution will be in the water and draining that would get rid of more calcium.

Is the Scaletec and Beautech addition mentioned in the no drain thread an important step? I'm not clear about what these materials are.

Aquatica,

The pool is new to me, not sure how to identify Marcite vs the alternatives. Thanks for the advice re: Diamond Brite if I make the move toward refinishing.

 

[duraleigh]

I don't know anything about those products. Perhaps others will weigh in.

You can do the math and see that, with a fill of 290CH, it's going to be a while to get that down. I don't know how much rain you'll get but it sounds like that's what you are counting on.