Slippery green steps and ledge, plus some stains

[needsajet]

I've got my work cut out for me. My mother-in-law's pool is around 15K gallon, 45 years old, plaster, with slippery green steps and ledge. Her pool guy hasn't shown up for a month and won't return calls or texts. 40 degree weather (105 F) so guess who?!?

She's pretty stressed (mid 80s) so we had a cuppa and she told me about the pool. She puts $50 in a puck container and the pool guy comes every few weeks and brushes the pool and backwashes the filter. He fills the floater with around 2 or 3 lbs of trichlor pucks and leaves her another 2 or 3 lbs to put in later. Long story short: 180 ppm CYA and I've drained/refilled 10% twice (just down to plaster because it's so hot). I'm hoping for a cloudy day to do a couple or three more deeper drains, then SLAM.

My question is about the stains. Trichlor doesn't change them nor does vitamin C, so maybe copper from cheap algaecides? It seems somewhat likely given the history. If I'm going to do all this draining, why not chelate the metals, if they exist, before draining? Are there downsides arising from using the sequestrant? With Christmas coming and this pool being across town, I don't have much time to get the pool in shape for a favourite swimming time.

Thanks so much for any/all thoughts on this!

 

[Texas Splash]

If you rule out the organic staining with the tabs, and vitamin C doesn't work for iron, it's possible it's another metal like copper. But vitamin C can make a copper stain darker, so I'm guessing it didn't do that either right? You could try some dry acid if you have any lying around to see if that does anything. There's also Magic Jack's stain kit if you feel like spending a few bucks. Lastly, if the stain is dark and rough it could be calcium - perhaps with something embedded in it. Hope those thoughts help you crack the code on the In-Law's pond.

 

[JamesW]

You might be dealing with multiple issues.

Possibly black algae and perhaps metal stains.

Can you scrape anything off of the plaster?

Do you have pictures?

 

[needsajet]

Pat and James, thanks very much. I was out of commission today, but will get on this tomorrow morning and fill in some blanks, hopefully including pictures.

I didn't notice the stains getting darker from the trichlor puck, but I'll try it again and look for that. I'll get in the pool tomorrow and see if anything can scrape off. I'll also try some dry acid and see what happens. I haven't been able to find any Jack's products here.

The forecast is all hot and sunny until Thursday, so it will be a few days before a larger drain/refill.

Thanks again.

 

[needsajet]

I'll attach some pictures below. I haven't tried the dry acid yet, but did try vitamin C and the trichlor pucks again. I see stains that are brown, blue-green and black. The brown ones appeared to be lightened by vitamin C. The blue-green ones were not affected by the trichlor pucks, but may have darkened very slightly; there are before/after pics below.

Back to my original question, I'm getting the impression that there's no particular downside to using an HEDP sequestrant, but I understand it won't do anything unless there are metals to sequester.

Here's the pics:


Pucks on blue-green, before/after


Blue-green on wall


Brown stains on top step, lightened by vitamin C


Black spots, not many of these, haven't started trying anything on them yet.

Thanks again for your help with these!

 

[Texas Splash]

I tend to agree that you appear to have more than one issue happening in the pool. We know there's some organic issues from the slippery stairs. That's an easy fix in itself. Any residual staining might take more time. But the more aggressive staining could still be calcium-related and/or metals. If metals were introduced somehow over time, then you probably know the more water you exchange to help lower the CYA will also remove potential iron/copper (perhaps from the pool maintenance guy), and also lower CH if it is elevated. Speaking of which, I don't think we've seen test results on your mother-in-law's pool. Now might be a good time to put everything together. The black spots could be black algae or, depending on their texture, calcium-related as well.

Treating some of the staining typically falls into the areas of scrubbing and/or AA treatments which might help overall. But before doing so, you would want to exchange as much of the water as possible so that you can SLAM properly. The final step, if you chose to use it or even need it at all, would be the sequestrant. The sequestrant won't remove stains, but should help prevent future build-up once the SLAM is completed. You don't want to apply sequestrant before the SLAM (or AA treatment if performed) because the elevated FC will reduce the effectiveness of the product. But if there is no new iron/copper being introduced to the water after exchange, you may not need it.

Let's see if James sees your update. He may have another thought or two as well.

 

[JamesW]

Looks like old plaster. Probably erosion, pitting, scale, copper, iron and black algae.

 

[JamesW]

You can do a full SLAM for the black algae, but that risks making the metal stains worse.

Alternatively, you can maintain a 15% fc/cya ratio and brush often. If that doesn't work, you probably need a full SLAM.

Some spots look like gunite showing where the plaster has worn down.

With the plaster in poor condition, black algae has a place to dig in roots.

 

[needsajet]

Yep, definitely old plaster I'm sure you can see the spots where it's worn away down to the concrete.

Here's the test results from my first test:
FC 9
CC 0
pH 7.8
TA 100
CH 450
CYA 180

I adjusted pH to 7.4 and have been keeping FC between 10 and 20 ppm. All the slipperyness is gone and the water is nice to swim in. The pool is consuming about 2.5 to 3 ppm FC per day. I'm exchanging water each chance I get, and after three X approx 10% exchanges, the CYA is hopefully down to approx 130. I'm hoping for a cloudy day on Thursday, and a chance to drain 30% of the water, then I'll need to repeat that one more time before I can SLAM.

So you gents reckon that if I added sequestrant before those bigger drains, it wouldn't help take more metal out?

 

[JamesW]

Sequestrants can lift some stains, but they're not great and might not do much.

 

[needsajet]

Thanks I appreciate that. So far, I've explained to her that I can only get rid of the algae and make it easier to maintain. Her neighbor is a top bloke (more like a son to her) and he's willing to add liquid FC once I get it in shape. He has a SWG pool, and it looks excellent, but he also talked about a few pool store potions.

I forgot to mention, I tried some scraping and nothing seemed like calcium scale to me, but that isn't saying much due to my lack of experience. I'm hoping that with a history of trichlor and 450 ppm CH it isn't too bad.

I'd mostly just like to get the metals down so it doesn't get any worse. She's not overly bothered by the stains. It's more just me wanting to do all I can realistically, knowing it needs plaster, but unlikely to get it. I'd also like to avoid any risk of adding to the stains when I take the FC up to SLAM.

 

[Texas Splash]

I'd also like to avoid any risk of adding to the stains when I take the FC up to SLAM.

Hopefully your pre-SLAM water exchanges will lessen the amount of metal precipitation to the surfaces. Good luck!

 

[needsajet]

I got in and went over things a bit more. Half a dozen bare gunite patches. Innumerable calcium nodules, mostly tiny but a couple of them were the size of a 10 cent piece (US quarter). Nothing I would call calcium scale, but I only really know what recent scale feels like and what a fingernail does to it.

I added a HEDP sequestrant at its high rate, and I'm keeping the FC at 10% to 15% of my estimated CYA (down to around 125 ppm). My MIL says it already looks as good as it has for years, so that's a positive! It was much more bearable getting in the pool and doing the brushing from there. (44C 111F today, and pretty humid as well)

 

[needsajet]

The water is looking good, but of course the plaster didn't magically get any younger!

I drain/refilled with the cold fill water coming in at the deep end, and removed water from the surface at the shallow end. Drain/refills were 10%, 10%, 10%, 5%, then 30% and 26% once I got my submersible pump set up. CYA went down from 180 ppm to 70 ppm and Calcium went down from 450 ppm to 200 ppm. When I checked the math, it looks like each drain/refill kept the fill water / pool water well separated. Pool water was 82 to 86F (28 to 30C) and the fill water was 72F (22C).

Then I let the FC drop, dropped the pH to 7.2, and SLAMed at target of 28 ppm FC (topped up to 32 and sometimes down to 22 after a hot day). No new staining appeared. I got an OCLT pass on the 2nd night, but did 2 more to be sure. I had been maintaining 15% FC/CYA until I could SLAM, so I guess that helped.

While that was going on, I did a few "pucks on the black spots" 10-20 minute treatments and some brushing of the spots with the stainless steel brush. My MIL thinks the spots look better, but I'm not convinced yet, so I'm maintaining 15%-20% FC/CYA. The water is looking great, especially after I took a robot over to give it the final clean.

Here's pictures of my drain/refill setup: