Lots of fertilizer in pool

[soxlover]

Hi there,
I'm pretty new here but I've been in the pool business for 13 years. I ran into something new today and would appreciate some advice. I went to clean a customer's pool today and got a big surprise. No, there weren't any topless girls sunbathing around the pool. I discovered that they had covered a very large lawn with lots of fertilizer. When I started brushing the pool I saw that the bottom had a layer of the stuff. I'm concerned about a couple of things:
1. Iron staining.
2. Trouble with algae.
I'm wondering if I should just drain this thing. Any ideas? Water test results were as follows:
chl - 4.0
pH - 7.6
Alk - 130
CYA - 80
I don't have an iron tester since I've really never needed one. It's a salt water pool too.

 

[chem geek]

I wouldn't worry about the contents of normal complete fertilizer which have nitrogen (ammonium nitrate or urea), phosphorous (usually as phosphoric acid) and potassium (usually as potash which is potassium carbonate). They do not always have iron so you really won't know if there is a problem with iron unless you test for it. It is probably a good idea to collect as much of the material as you can and vacuum to waste or otherwise remove it. Be sure to clean the filter as well. If there is iron, you can use a metal sequestrant to bind it and possibly help remove it through coagulation/filtration.

Though the phosphates and nitrates may make the pool more "reactive" with respect to algae growth, it can certainly be controlled through appropriate chlorine levels as shown in the Chlorine / CYA Chart.

 

[JasonLion]

You said that "chl" was 4. I assume that means that you used a total chlorine (TC) test, like the OTO test (drops turn the sample various shades of yellow).

If there may be fertilizer in the water, you really want to distinguish between free chlorine (FC) and combined chlorine (CC). FC reacts rapidly with fertilizer and converts to CC, until all of the ammonia compounds are converted to CC. Subsequently the CC is further broken down and vanishes. If there is fertilizer in the water you will see FC at zero and CC above zero (at least at first). Meanwhile, if you can confirm that there is a reasonable FC level, then either no fertilizer got into the pool, or it was all completely broken down already.

 

[Richard320]

Hi there,
I'm pretty new here but I've been in the pool business for 13 years. I ran into something new today and would appreciate some advice. I went to clean a customer's pool today and got a big surprise. No, there weren't any topless girls sunbathing around the pool. I discovered that they had covered a very large lawn with lots of fertilizer. When I started brushing the pool I saw that the bottom had a layer of the stuff. I'm concerned about a couple of things:
1. Iron staining.
2. Trouble with algae.
I'm wondering if I should just drain this thing. Any ideas? Water test results were as follows:
chl - 4.0
pH - 7.6
Alk - 130
CYA - 80
I don't have an iron tester since I've really never needed one. It's a salt water pool too.

Maybe you got lucky and they used the slow-dissolving "all-season long" lawn fertilizer. In which case, vacuuming it up and getting rid of it ends it all right there. But what the heck - go for the upsell anyway and recommend an iron test and a chlorine shock.

It could have been a lot worse - what if they used fish emulsion?