8 months into new pool, first signs of algae


Well-known member
Feb 22, 2017
Pool was completed November 2018, and eight months later we have the first signs of algae in the corner of the spa. After reading the first page I feel silly even posting about this, so I'll take the ribbing like a champ. :) TC has been between 1 and 2 the past four weeks using TF-100 (and I just tested the spa is at .5, pool is 1.5). And the Intellichlor pool output has been at 20% and spa at 3%. It's been 90+ degrees with tons of rain and I've had to dump 18 inches of water during this time span (great for getting my calcium levels down, not so great for chlorine generation). With that as a backdrop, here are my questions:

1. Outside of scrubbing the algae off should I do anything else? Maybe dump some chlorine in the spa and let that percolate for a bit, a mini slam if you will?
2. Intellichlor pool output is 20% and spa 3%, and my chlorine levels have hovered between 1 and 2 for several weeks. Should I up this output and to what?
3. Why do I have separate pool and spa output when it's all one system? Does the spa output even matter if it's circulating?
4. Separate but related question, when we originally programmed the pool we turned on the returns for the pool and spa so we could have the spill over affect and keep the water circulating. For some reason the spa return stopped working during this schedule the past couple of weeks probably contributing to the algae (FYI spa returns work fine when we run the spa or waterfall feature). For the life of me I can't figure this out. How do I fix this?

Pool specs
13000 gallon pool and 800 gallon spa
Pebble tech finish
Pentair IntelliChlor IC4
Pentair S7MD 72 D.E FILTER
Pentair 140 BTU Heater
2 Pentair intelliflow variable pumps
Pentair screen logic system

Latest TF-100 results
TC 1.0
pH 8.2
TA 70
CYA 55
CH 475 (and going down cause of all the rain)
Salt 4000

Last edited:


Well-known member
Jul 7, 2014
Hope Mills, NC
55, round up to 60 x .8 = 4.8 + 2 = 6.8, call it 7.

Aim for 7.0 FC and never let it go below 4.8. That's why you have algae. Time to SLAM.

Quick and easy method to get close to the FC/CYA correct ratio.


Well-known member
Feb 22, 2017
Is slamming necessary for that little algae? It's literally just that one spot in the spa with nothing in the pool. Was hoping increasing the salt output would be sufficient, or maybe just slamming the spa. Or are you suggesting a slam as a way to avoid a potentially worse situation and get to higher levels faster?
Last edited:

Flying Tivo

Well-known member
Jan 24, 2017
Monterrey, NL, Mexico
If in spa mode you have the spillway active then the SWG should be the same % as in pool. If you are going to run the independently then the % should be lower in the spa due to the volume. Slam Time, hit it hard and often so it will go quickly!