Getting rid of nitrates?

jtblaw1

Member
May 9, 2010
9
My pool has mustard algea that I cannot get rid of. Water is clear, just growht on the walls. My free chlorine level is always low. Pool store guy told me I have nitrates from lawn fertilizer that got into the pool and this is what is eating up the chlorine. He told me to lower my water level apx two feet and re-fill to rid the nitrates. All other numbers are fine. Help?
 

lightingguy

LifeTime Supporter
Jun 17, 2010
513
Glendale, CA
Couple things:

Do you have any reason to believe you have a lot of fertilizer runoff into your pool?

Also - more information would help everyone here. A full set of test results, how you chlorinate your pool, etc. etc.
 

jtblaw1

Member
May 9, 2010
9
I have no reason to believe that nitrates got into the pool other than potential overspray of a spreader for the guys that fertilize my lawn. I have never seen any dry fertilizer on my pool deck. The guy in the store ran the nitrate test and told me the nmber was "15"

In any event, the numbers are:
fc 0.0
tc 0.3
ph 7.7
hardness 240
alk 80
cya 50

I chlorinate with an automatic chlorinator and have it open all the way. I know its working in that i just cleaned it about one month ago and the tablets are dissolving in due course. For some reason, despite the fact that the chlorine tablets are dissolving and I fill up about twice per week, i cann't get the fc level up. Is it possible that the algea is using the chlorine? Also, I've put a lot of algecide in over th past month. Could this have an affect?
 

lightingguy

LifeTime Supporter
Jun 17, 2010
513
Glendale, CA
the Algae is definitely "eating" the chlorine faster than the slow dissolving tabs can handle. My guess is you have very little issue with Nitrates - "15" or not.

You should spend a little time in the Pool School found here to help you get a better handle on how your pool chemistry works. Here are the basics -

As Chlorine cleans you pool it gets broken down. That FC number is the "good" chlorine - the kind that would go out and kill algae. Without any the algae is able to keep growing.

Algecide is usually better at preventing algae than killing it once it's growing.

You need to shock your pool in order to kill off the algae. You can find instructions for this in the Pool School.

You can use the Pool Calculator - http://www.poolcalculator.com/ - to calculate how much chemical you might need.

Post more information about your pool - people here like to help
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
Nitrates are not the problem. The problem is that you have not been shocking the pool properly, so you have never completely gotten rid of the algae. Do some reading at Pool School and think about switching to a form of chlorine that doesn't constantly raise your CYA level.