Silt, sand, mustard, pollen...what is in the pool?

J_L_D · Mar 27, 2013

Just had new liner, and converted to SWG. Everything seemed good, but I keep finding brownish deposits and dust on liner. Same as last year, and hoped new water would have cured it. At first thought broken lateral and was sand, but now think that it is mustard. Have read scores of blog discussions on it and want to try to treat for it, in case. After raising FC it seems better, but of course I'm still not positive that it is ... I mean did it just live in my filter over winter and bust out when I started up last week?.

The pool company started it week ago and brought FC up to 10 (with cya 0), which I let settle to about 3 before turning on SWG, and keeping around 3 or 4. Backwashed on Monday and it was dirty, cleaned with the 280 and looked good Tuesday morning so ran filter all day and SWG at 30%. Came home to brown deposits, even more than before, plus sort of sticking to sloped wall (shady side). Fc was around 3, decided to start shocking in case mustard.

Turned SWG to 100%, after brushing. Fc was up to 9 by 10:00 last night and I saw less brown this morning. At 6:00 pm FC was 19 but still some brown. Checked at 10:00 and came up with FC 17 (best i can tell swg would have added at least 2 ppm during that 4 hours, not drop 2)...so maybe I'm killing something?

I can't check cc due to no reagent but here is other

FC..17 and leave swg at 100% all night?
CH - 20
CA - 45
TA - 110
Salt - 3200
PH - was 7.6 but not accurate now, right?

Should I keep going with swg? I'm worried about damaging liner ...could be 30 FC by tomorrow night.

duraleigh · Mar 28, 2013

The only way you can correctly identify if you are killing algae is to turn off the SWG and shock the pool with liquid chlorine. You may be killing some or most of it now but the SWG keeps replenishing your chlorine masking the chlorine loss that would indicate the presence of the algae

read "How to Shock Your Pool" up in Pool School. Follow that process exactly (without the SWG) and I think you will solve your issues.

J_L_D · Mar 28, 2013

Update for anyone interested...mustard, silt, sand, and Spring pollen are tough to diagnose. In my case it's been plus new system, lots of windy weather, much pollen, and some drainage improvements in the yard and dirt.

Pool is MUCH better tonight. Just a few spots of brown in the depressions, plus a light 'dust' on some surfaces when I brushed. Water is crystal clear, but it already pretty much was. I turned off the swg, as planned, last night but kept filter on. I think the 17 fc was off, because I got a 22 this morning. Continued to run filter today, no swg, and had 16.5 FC at 6:00 pm (sunny all day, 65 degrees). Brushed a bit, turned on the 280 and continue with filter. Had about a pound of sand in the knee high hose inside the filter bag. The shady slope (which is also where a return is) was pretty clean. Could have been combination of things, but the shock level seemed to help...now to decide if go higher or let it come down... never did hear about potential damage to new liner at high fc, but hopefully all good... It was bumping around mustard level, especially with cya being a bit subjective, but will let it come down and see if it reappears, I think. I read here that is a sign it was mustard vs silt, pollen, etc...

As for shocking with swg, I followed the written steps 2 and 3 but with swg vs. liquid. Instead of adding at least twice a day, I added continuously to maintain, then turned off overnight. Have battled and won with mustard before using liquid, but if swg has capacity...why not...it's easier

. I don't know why swg is stated to be effective at lower fc level (than liquid) during normal operation, but not while at shock levels...and have read here that chlorine, is chlorine (excepting the additives within). But so far, so good doesn't mean I've won...will post back if it comes back once down to 3 ppm FC.

Now I'm thinking add some DE to the filter...hmmm.

msgtdan · Mar 29, 2013

I think the two main reason to turn off the swg when shocking is the masking of chlorine usage which you're taking into account. And the added wear and tear on the finite life expectancy of the cell. As long as you're aware of both those and take it into account, then if the swg will bring you to shock level you can do so.

anonapersona · Mar 29, 2013

If you have pollen on the car, you have a lot more pollen in the pool.

Just took time to wipe down the black interior of one car.... pollen all over the dash and everywhere, but if you didn't notice the pile of it on the edge of the door, simply closing the door would have blown pollen all over the interior again.

duraleigh · Mar 29, 2013

but if swg has capacity...why not...it's easier

yes, but....

One of the advantages of liquid chlorine is it SHOCKS the pool....an immediate dose of high chlorine levels which can really get a good quick kill on much of the organics. Most SWG's will raise the chlorine slowly and, IN MANY MANY CASES, the SWG is not powerful enough to eliminate a high level of organics so you end up killing some while some more grow..... sort of a standoff. Shocking a pool correctly needs a high dose of chlorine and then that high dose of chlorine needs to be maintained.

J_L_D apparently has a very strong SWG and/or not that big of an organic load so it is working in his/her case and he doesn't mind the expense of the wear and tear on his salt cell.

So, for newbies reading this, it is always a good idea to shock with liquid chlorine and to shut off your SWG during the process.

J_L_D · Mar 29, 2013

Good points, all. And I hear ya, duraleigh, on liquid being a more reliable and measurable method. That is the 'gold standard' method. And it's true that I don't really know what my organic load is/was. Dirt, pollen, mustard or some mix, who knows. But I'm glad I took the FC up to where I can hopefully eliminate part of the problem or even rule it out. Does that also breakdown pollen and/or 'dead' pollen?

And I also don't know how fast (or if) the SWG would get me to 22 ppm FC in the dog days of summer. The CPSC-48 is supposed to be rated for 2.5 lbs/day. If I've done my math and used the pool calculator correctly, and if my pool is 21,000 gallons (That figure estimated based on addition of salt and pool calculator), and if my FC tests were accurate (I put all those If's in there on purpose - your results may vary !!)...then when I raised FC from 9 to 19 in 20 hours, it was averaging 2.1 lbs/day. Assuming some of it was used up during the daylight hours, plus any organics it killed, I'd say it's pretty much in line with specs. I didn't mind running 100% for a day, as sometimes they are run like that almost constantly. It says it's rated for 60,000 gallons but I'm sure that would be 24/7 100%, as they are all rated, I do believe. I have no idea yet what number of hours or % I'll need in full summer. Don't know if that will help anyone looking at the Compu-pool SWG's.

anonapersona - YES we have pollen - everywhere. Can't really see it on the pool apron until it gets wet, and turns to yellow paste. I can't imagine how much is going in the pool. But the skimmers and filter are working overtime and hopefully the rain this w/e will help clear things.

As always, thanks for the input and the great website. DE in Sand filter is next, to see if it really will eliminate the floaties with the light on at night.