Chlorine usage with SWG and stain??

Hexumaz · Jul 23, 2014

Started up our new DIY build IG pool a few months ago and the pool/water look great with all the info gleaned from this forum! My pool is about 15k gallons, free form design, play pool depth (4-5.5-4), with a pebble sheen interior. All Pentair equipment including a VS pump, IC 40 SWG and Easytouch automation panel. I run the pump about 9hrs total at varying speeds and times of day, with and without the fountains running (2 deck jets, 48" sheer and 2 wok pots....trying to cool it down!). My water temp fluctuates anywhere from 86 up to 90 according to the Easytouch temp sensor (not surprising since I am in Phoenix and its HOT!) I started my SWG at around 30% and found that I was still having to add quite a bit of liquid chlorine to stay in the 3-5ppm range. I have subsequently bumped up the SWG % several times and am now at 70% but am still adding 1/2 gallon of liquid chlorine every couple days to get back to 3-5ppm. My chemistry seems to be pretty good otherwise although my CYA was still a bit low so I have upped that. PH still creeps about every 3 days and I am adding about 1/2 gallon of MA. Test results from this morning were:

2 FC
.5 CC
350 CH
90 TA
65 CYA
7.8 PH

As I said, water looks great so I dont think I really have any issues, I was just curious if I should have to be running my SWG so high to keep up? I know its hot here and we do swim everyday (6yo and 4yo girls ) so is that just the nature of the beast?

My second question is regarding a rust spot/stain I have on one wall. It is about the size of a quarter and appears to be growing out of the wall? No other stains anywhere in the pool. Might I have a small crack in the pebbletec and the shotcrete letting water into a piece of steel? I have not been able to perform the vit c test on it yet. Any input is appreciated!

jblizzle · Jul 23, 2014

You should raise the CYA up higher and then either increase the pump run time or increase the SWG output until it maintains your FC level.

Being the stain is on the wall, I would guess that there is some rebar too close to the surface that is rusting.

dradam · Jul 23, 2014

If you are not using intellichem then you can get your cya up to about 100. This may help stabilize the free chlorine. You may find that running the pump 24/7 will allow the chlorine generator more time to make chlorine. I run at 15gpm which has enough flow to keep the swcg flow switch on. At 250 watts it is worth the electric cost to me. In a very sunny environment you may need to go a bit higher with you swcg chlorine level . In an open pool more sun more chlorine loss. Consider a cover as well. Your swcg should be more than enough for a 15k pool, but I'm glad you oversized.

If your tired of adding acid consider intellichem but it is a finicky system at best.

Lastly, Sound like your pool is new. Are the pebbles in plaster? if you had new plaster you should have filtered for a month without your SWCG in place. New plaster can affect the function of a SWCG (pentair offers a tubular space filler for this).

as for the spot-- likely a rusting metal grind it out for next season and reseal.

jblizzle · Jul 23, 2014

TFP recommends a CYA of 70-80ppm for a SWG pool ... 100ppm is excessive.

Hexumaz: Please add your location (City, State or City, Country) to your profile and pool details to your signature as described HERE as it will help us help you in the future.

bobodaclown · Jul 23, 2014

With a CYA of 65 your FC should never be below 3.
http://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock

You never want a CYA of 100. Just too many problems, it happens a lot, but not something to strive for.

Flatlander · Jul 23, 2014

Hex,
Mine is a carbon copy with the same issues. I'm running vs at 1950rpm, 12hrs and IC at 30%. I have added a 4th gal of liquid conditioner today and 1/2gal of MA every 3-4 days. I am going to increase IC to 40% and see if that maintains. Water is clear though. My plaster is very mottled in a portion of one end too.
Never the perfect pool I guess!
Keep us posted with your numbers, I thought it was just my pool.

pooldv · Jul 23, 2014

20k gal gunite in DFW with pentair VSpump and IC40. Run the pump 24x7 at 1100 rpm, mostly for extra leaf skimming. Pump jumps to 1950 when solar turns on. I have the IC40 at 20% right now, it is close to needing to bump to 40% because we are in it all the time. We are not in full sun though, hence the solar panels running, and we like the water at 88-89.