High FC in saltwater pool - can't figure out how to lower it

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J

juniper55

0
Jul 20, 2012
29
Hi everybody, I'm a newbie and this is long.

Saltwater Intex pool, 3200 gallons, in the shade. Second year, this year we put a 12X12 canopy and mosquito netting (they're fierce) which keeps most debris out (but daddy long legs still get in...)

Last year we had no real problems other than keeping stuff from the trees out (hence the canopy). Used Intex and HTH test strips all summer, added AquaChem shock a few times (half a bag at a time, max) because of the tree debris but didn't seem to have any water chemistry problems other than the pH ran around 7.8-8.2 (I know why now).

Like last year, I try to vacuum every 3-5 days and change the filter about once a week, we get a good bit of sand blown in. We got the salt right at the beginning and added the HTH stuff for starting SW pools for CYA/cell maintenance as we were filling.

This year - started out OK but after the first week I began noticing this strange white stringy waxy stuff in the water in mid-June. Brand new pool liner (last year's was punctured with tree branch from H. Isabel).

I thought it was white mold, so I searched the internet then added about 2-3 lb of HTH pH Minus to bring the pH down (8-8.5 with test strips and I was following package directions) before trying to shock the pool.

The pH dropped to under 7 so I guess I added too much, but there was no new white stuff. I added 1 lb bag of AquaChem Shock Ultra (orange bag) from Wal-mart to kill the white stuff and added a few inches of fresh water to try to bring up the pH.

A couple weeks went by, we had some storms and didn't use the pool much but by the end of June the FC was showing as 10 or higher on the strips, the pH was creeping up again to 8, the TA was 40. TH and CYA seemed ok so I tried more water and 3-4 lbs pH Minus. This time I think I added way too much! I wasn't seeing any more white stuff but was starting to see some brownish slime on the strainer that was hard to scrub off (no where else though). I had been adding HTH Natural Clarifier for floccing but saw somewhere that that was not a good idea so I stopped.

The pH dropped to under 6.8, TA 0-40, TH 100-200 and CYA 0-30 with test strips. So I added 1.5 lb stabilizer to bring up the CYA. This was July 2. From then to about the 8th the pH was still low and the FC was staying at 10+ (very dark purple on the test strip) so again I added water and about 1 lb ph Plus this time.

I also bought an HTH 6-way drop test kit on July 11. It said my combined cholorine (OTO test) was out of range (very orange), and the test strips still said 10+. Red phenol pH 7-7.2, strips a little higher. CYA drop test 90-100, strips 50-100. The TA and TH tests were wacky because the colors didn't match the instructions (and still don't today) but I think TA 40-80 and TH around 100.

Our weather has been very hot and dry for a few weeks now, several days in 90's up to 100 and lows in 70s (mid-Atlantic). No rain in forever at our house. We use the pool about 15-30 minutes a day almost daily but not in the past week. Pump runs 24 hours/day since opening, SWG 6 hours daily.

Water getting a bit of a green tint. Copper readings using Intex strips staying 0.2-0.5 since opening. Changed filter as usual and this one had bluish-green color for the first time.

Then I found this website and poolcalculator.com. I read several sites about what levels for SWG should be, put in the numbers and my data, added half a jug chlorine bleach and a 1-lb box of baking soda (all I had at the time) per instructions. Yesterday I bought new test strips since mine were from last summer, checked again with test strips because I was too busy to do full drops and the pH was up again so I added about one lb pH Minus.

Pool looks fairly clear but now has a greenish tint. Second filter switch out and it is blue-green again. Reminds me of copper from chemistry classes but pool is starting to smell bad. I see nothing in the pool but the usual bottom debris and DDLs. I examined SWG and see scale formation.

I am convinced I need a Taylor kit and am going to find one.

Data this morning using my stuff on hand:
HTH strips Intex strips HTH 6-way drops
FC 10+ 5-10 CC >5 (OTO) very orange
pH 6.8 8-8.5 7.2 (red phenol)
TA 40-80 100-150 40? (blue rather than green -> yellow but not red)
TH 100-200 150? (yellow -> light blue)
CYA 50-100 100 (black dot)
Copper 0.2-0.5
Salt 6.4 -> 3130
Temp 79.5

Pool calculator says I should add some more washing soda or borax (I have HTH ph Plus) and about 1-1/2 boxes baking soda, also I should drain about a quarter of the water and add fresh to bring down the CYA.

What I don't get - why does the FC stay so high and how do I bring it back down?

Should I drain some water out of the pool, add fresh and go from there?

Should I shock the pool again, and is the orange AquaChem ok or should I just add plain chlorine bleach?

Many thanks!
 
Re: High FC in saltwater pool - can't figure out how to lowe

First thing you need to do is get better test results. But you already know that.

I would simply run the swg a shorter amount of time. With a CYA over 100 it'll take a while for it ot come down but also because the CYA is over 100 it may not be too high.
 
Re: High FC in saltwater pool - can't figure out how to lowe

Just make sure the kit you buy has the FAS-DPD test (K-2006 or the TF-100). You will likely have to order it as it is unusual to find locally.
 
Update - Re: High FC in saltwater pool

An update for my 3200 gallon Intex SWG pool with copper ionizer. The SWG runs 6 hours a day and the pump runs round the clock.

I took a water sample to a local pool store. They appear to have tested with a LaMotte WaterLink, or something very like it. They had the little UDVs and gave me a computer readout. This was last Friday's results:

FC 0.86
TC 1.26
CC 0.4
TA 0
pH 6.6
CH 111
CYA Did not test
Cu Did not test
Saturation index -3.2

They said: add 1 lb shock and 6 oz algaecide and brush down the pool to kill any algae. Then wait. Then add 2 lbs alkalinity increaser. Then wait. Then add 1/2 lb pH increaser. Bring back water sample and retest.

I added the shock and agaecide Friday afternoon. Saturday morning the filter was no longer tinted blue-green but did have some blue-green-yellow lumps. Grayish stuff on pool floor. Brushed, vacuumed, changed filter. Added the alkalinity increaser. Late afternoon I added the pH increaser. Sunday morning I tested with my 6-way HTH drops and strips and they all said pH was 7.2 and TA was 40 (strips) and 75 (drops). The CC with the OTO was still very orange.

Today I took a new water sample to the pool store. This is today's readings:

FC 0.21
TC 7.67
CC 7.46
TA 0
pH 6.9
CH 129
CYA 12
Cu 0.9
Saturation index -2.8

Today they said: add 3 lb alkalinity increase, 1/2 lb pH increase, 2 lb calcium. They told me I could use some "metal out" but shouldn't until the rest is under control. They ordered me a Taylor kit and I'll pick it up Thursday!!!

I am guessing with the high TC and CC that any algae is being killed but with the FC so low now with this test, the Pool Calculator says I need to add 25 oz of bleach to bring up the FC to 4. Some other stuff I'm reading here suggests I should add borates (none in there I know of) and boost my salt a bit to help maintain FC and pH levels better.

Is it unusual to have to add up to 5 pounds of alkalinity increaser? Shouldn't something have registered the second time?

Should I add more salt or more bleach? No warning lights on my SWG to tell me it isn't working. Doesn't high chlorine mess with accuracy of testing for other stuff?

Thanks to all for your advice!
 
Re: High FC in saltwater pool - can't figure out how to lowe

You are going to have to decide whether to take the advice given here, or if you are going to follow the pool store's recommendations.

You can use soda ash, borax, or aeration to raise your pH.
I have never seen a TA of 0.

Those numbers indicate the need to go through the shock PROCESS, not a shock product. You are going to need that good test kit to do this. Look at tftestkits.net for the TF-100 or K2006.
pool-school/shocking_your_pool
 
Re: High FC in saltwater pool - can't figure out how to lowe

I asked about the 2006 (I might have called it 2005 by mistake). They talked to their supplier (truck coming in tomorrow), I didn't catch the number. Will have to wait. I know I want the extended capability for differentiating chlorine but I failed to mention it at the store.

Going to the store now to buy straight bleach and some borax.

I'm confused on the order of things - should I get the chlorine under control first, then do the pH/alkalinity?

Or should I do the pH/alkalinity first?
 
Re: High FC in saltwater pool - can't figure out how to lowe

Pretty clear to me. Can't tell how sparkly since under a canopy. Filter full of blue-green again, kind of slimy. Changed it. Nothing on pool bottom except daddy long legs and a little debris. I did add one more pound of alk. increaser, figured that was the least harmful.

pH was 7.5 using HTH phenol red. CC very orange with HTH OTO. TA was 100-120 switching from aqua to yellow using HTH but I read on the Taylor website looking at their 2006 kits that if I'm seeing these colors there might be a high halogen level (isn't chlorine a halogen?). Brand new bottle of Taylor R-0013 and black dot test said CYA was about 80.

Now pH should be the simplest thing on the planet to measure. How could theirs be so different than mine?????? If I can't get an accurate pH test everything else seems to be up in the air.

Going to buy bleach and borax for real this time and keeping it on hand! and longing for that new test kit.
 

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Re: High FC in saltwater pool - can't figure out how to lowe

The Taylor K-2005 is no better than your HTH 6-way kit. A little better, it has better quality reagents but as far as the results it'll give you, no better in any way. Don't pay for a K-2005. It's a waste of money in this case.

As Robbie mentioned, you really need to decide which method you're going to use. The pool store is having you dump this and that into the pool, you have over 7ppm CC (WOW!) and you're putting product in one time and expecting it to shock your pool. That's not what we do here, and if your plan is to continue to follow their advice and buy products there's not a lot we can do to help you deal with your water problems.

FWIW, we don't get paid to sell you bleach and test kits, or any other laundry aisle products that you can use to manage your pool water chemistry. Pool store people do. Maybe this will help you decide whose motives are less pure :~}

There is one theme that I saw in your post that I'd like to mention, for others reading this thread. (I realize you're getting a better kit and that you now understand why you need it but others may not see what I saw in your history)

The entire history you wrote up about your pool shows how the test strips not only provide inaccurate results, they provide you with the means to seriously gork up your water. Every time you used something to adjust the water based on the test strips, you ended up missing the mark. Then you added something else to fix it, and it was gorked the other way. Over and over this happened to your pool. It just shows how the strips end up being worse than nothing much of the time. It would have been so much easier and cheaper to have an accurate test result, which allows you accurate measurements of products (pool calculator), and you very likely would not have experienced the bouncing around and expense of products that were unnecessary.
 
Re: High FC in saltwater pool - can't figure out how to lowe

RobbieH said:
You are going to have to decide whether to take the advice given here, or if you are going to follow the pool store's recommendations.
Click to expand...

I have to reiterate this!!!

Just based on how different your tests are from the pool store you will be just confusing yourself if you try to listen to both.

If your CYA is 80ppm, you are perfect. If it is 12ppm, you need a lot more.
If you TA is 100ppm, you are perfect. If it is 0ppm, you need a LOT of baking soda.
If your pH is 7.5, you are perfect. If it is 6.9, you need more borax/soda ash/aeration.

Based on the "excellent" match :roll: between those tests ... how much do you trust their FC and CC???

Make sure you get the K2006 ... or you will have to order the FAS-DPD chlorine test separately.
 
Re: High FC in saltwater pool - can't figure out how to lowe

I looked at the Taylor site and printed out the component lists for both the K-2005 and K-2006 and went through the material sheets. I also found the Extended Test Kit Directions on this site and printed it out. I am looking forward to using the enhanced tests for calcium and what not.

Looks both are the same except for the chlorine testing. From the ETKD's on here the uncertainty of the DPD test seems pretty high. I did not see any values for the FAS-DPD. Is it really that much better? Anybody do any side by side comparisons? (I'll do it once I get the extra testing stuff :-D

Looks like good ole phenol red for pH test - that shouldn't be any different than my HTH kit, would it? What does the LaMotte UDV test do differently at the store?

Are y'all of a CHEAP test for copper? I have been using the Intex test strips and until I dumped the pool pH the readings had been around 0.1 - 0.2. Are those reliable, at least?

I am really grateful for your advice!
 
Re: High FC in saltwater pool - can't figure out how to lowe

If you have the HTH 6-way you don't actually need a whole K-2006 kit. The HTH has most of what you need already, except the extra CYA reagent and the FAS-DPD test.

If you're looking to save a few bucks you can buy only the reagents you need at TFTestkits.net. You can chose between Taylor refill bottles (.75oz typically) or the TFTestkits reagents which are Taylor reagents, re-bottled in larger bottles. Either works, but the TFTestkits refills provide a better value.

These are the reagents you need:
R-0003
R-0870
R-0871
R-0013
little blue scoop - $.15

With the cylinder from the HTH kit and the CYA cylinder you've then got a full kit that will serve your purposes nicely.

You can also buy the FAS-DPD stand alone kit, and the CYA kit but you don't need the cylinders so this is why I suggest the reagents only.

The FAS-DPD test is the one you want because it can test chlorine up to 50ppm and is NOT a color comparator test like the DPD. Your limit with the DPD is 5ppm iirc and it's next to impossible to get a decent reading of TC on a color comparator. The FAS-DPD test is much easier to use, you drop the reagent in till the sample goes clear. Far easier than distinguishing between slightly red and more than slightly red.
 
Re: High FC in saltwater pool - can't figure out how to lowe

I printed out the shock and overnight test instructions, got 4 gallons of bleach from WalMart and am waiting for the Taylor kit now. The store did have a bunch of single-bottle reagents as well as one or two overall kits. I will let y'all know how things come out! Thank you so much for the advice.
 
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