What did I do wrong?

[daveCBP]

I recently started a business servicing pools. I was called to a green pool, tested it and found these results:

pH - 7.8 FC - 0, TDS 1200, Cyanuric Acid 180...

So I figured that high cyanuric acid was locking out any chlorine, and surely the only way to lower CA is to dilute it? Same for TDS?

Anyway, I balanced the pH to 7.4, and after dumping about 2 thirds of the total water over the course of a week (as recommended by the pool calculator), the pool cleared up - job done, or so I thought - This was a week ago.

So today, I got an email asking for a partial refund - apparently their pool had gone green again, and they called someone else out who cleared the pool in 3 hours!

What the heck did he do? Or what have I missed?

I am still new to being in the business, and I don't know everything. Never heard of a pool going from green to clear that quickly. Is this some industry secret that I don't know about? What did I do wrong?

Help!

 

[frustratedpoolmom]

Playing the devils advocate, how do you know they are telling you the facts?

You did the right thing. Lowering CYA when it's that high is priority. Did you confirm the algae was dead after you treated the pool? How was the pool chlorinated following your visit? Was the chlorine level properly maintained after you were there? There are alot of variables here that could have affected the end result but I don't see why you should give them a refund, you don't even know if they are telling you the truth.... Who knows what he could have used, a traditional pool store method no doubt, and if that's what they want and they don't mind paying for it, then by all means. But you did the correct thing in lowering the CYA. And even if he did "clear the pool in three hours" you made it easier for them by lowering the CYA which required a lot less chlorine to do the job.

 

[duraleigh]

In your post, you do not say how you cleared up the pool. Lowering CYA won't do it. You had to use chlorine somehow.

Chlorine is a consumable item. It has to be added constantly to a pool ot it will simply turn green.

Regardless of how the other company cleared it, it will simply turn green again unlesss someone constantly puts in adequate amounts of chlorine.

 

[daveCBP]

The pool was cleared mainly though dilution, having replaced so much water, but yeah, I shocked as well, to 8ppm FC, to kill the algae and used alum sulphate as floc to remove it from the water. It wasn't crystal clear by the time I left, but it was greatly improved. I was working on a deadline, as they had a pool party coming up and wanted the pool clear. Had it been up to me I would have continued to work on it, as I wasn't satisfied that it was ready, but like I said, I was rushed.

The circulation in the pool wasn't great, so I stripped the pump and checked the impeller, all was fine. I backwashed regularly whilst I was there, and asked the customers to do the same.

I do suspect that they didn't dose the pool properly once I was gone, they had a dirty comparator for a test kit, and no idea what to do with the pool from day one - they had just moved in, and it was their first pool, so who knows.

This is the first job I have done that I have had a complaint about in a year, just a bit depressing to get one wrong... thought I had done everything right.

 

[crewchief47]

I shocked as well, to 8ppm FC, to kill the algae and used alum sulphate as floc to remove it from the water.

I'm still a rookie at this and haven't had to fight any battles of my own but if you did a 2/3rds water change all at once, that means the CYA would be at 60 at the lowest but your post suggests (over the course of a week) it's probably higher than that still. What I'm getting at is that the shock level for 60 CYA is 24 FC not 8. And it's even higher than that if the CYA is above 60, like I think your post describes. Unless I'm missing something.....

pool-school/chlorine_cya_chart_shock

 

[daveCBP]

I'm still a rookie at this and haven't had to fight any battles of my own but if you did a 2/3rds water change all at once, that means the CYA would be at 60 at the lowest but your post suggests (over the course of a week) it's probably higher than that still. What I'm getting at is that the shock level for 60 CYA is 24 FC not 8. And it's even higher than that if the CYA is above 60, like I think your post describes. Unless I'm missing something.....

pool-school/chlorine_cya_chart_shock

You have a point about the shock value. I was taking readings of 60-80 by the time I had to finish the job. I advised them to dilute it further, but I don't think they did. So if the CA was still too high, then whoever "cleared the pool in 3 hours" must have shocked to 24ppm like you say... which would be a lot of chlorine (not to mention pH adjustment and floc if he used it), yet he only seems to have charged them for half an hours work with no chemicals (so they told me), and of course without further lowering the CA level: so surely when the FC wears off, they'll be right back to square one? Following the chart, they would have to maintain an FC level of 10ppm+ all the time just to stay running right? And being that they're using Stabilised chlorine, that's just going to make the problem worse isn't it?

I would have been happy to drain 2/3 in one go, but it was a liner pool, and I never drain liner pools too much, in case the liner comes away.

TBH, I'm glad to be rid of them, I think they're going to have quite a few more problems yet, and this I don't need!

 

[MikeInTN]

Yep. If their CYA is 80, then they'll need to maintain FC between 6 - 9 to keep the pool sanitized. Using trichlor (stabilized chlorine) is just going to run their CYA back up again, and if they're not maintaining their FC, it'll be green again in no time.

 

[waste]

Let me tell you that you did nothing wrong! It would have been preferable for you to be able to do the job right/ completely - but as you say, you were rushed for time and gave them a swimmable pool for their party. To have a pool go 'bad' on you takes quite a while of constant neglect and there is no quick fix (other than full water replacement and surface cleaning) You did what they hired you to do, if they wouldn't pay you to completely get the water in line, no sweat off your nose

You care enough to come here to learn more about your trade so I'm sure this isn't malfeasance on your part

I have no clue as to what the other dude used to clear the pool in 3 hours, but I'll bet it had some unintended side effects :!:

You're better off not having those folks as customers

 

[anonapersona]

so would a copper treatment work that fast?

 

[daveCBP]

Thank you all for the replies , makes me feel a lot better about it. As I said, I'm still finding my feet in the industry, and it means a lot to me to do a job properly. Can't win em all huh. Really appreciate the welcome here too, I've only just joined the forum, but i can see it's going to be well worth it. Hope I can contribute plenty too