New to the forum and in need of assistance

[tideman]

I've been reading this forum for a few weeks now; very helpful information from a lot of knowledgeable people. I'm new here so please have a little patience, as I'm sure some of my questions show my lack of pool care knowledge. I certainly need and would appreciate some advice and guidance.

I have a 17,000 gal inground fiberglass pool, inline cholorinator using 3" tablets. Pump is 1 1/2 HP, filter Hayward cartdrige. I usually run the pump 8-12 hours a day. I've never experienced problems with water chemistry (knowlingly) until this summer. The pool has been turning green on the bottom w/greenish brown residue on the sides. I kept brushing, vacuuming, and cleaning filters and shocking, only to have it return after a day or so. I took a water sample to the local pool store here in San Antonio numerous times (getting a different recommendation each time). Hundreds of $$$ later I'm back to square one. Then I found this forum and immediately went out and purchased bleach, baking soda, borax, Muratic Acid, and CYA from the pool store. I also ordered and just received today the Taylor K-2006 test kit. While waiting on the test kit, I decided to shock the heck out of the pool. I used about 20 bags of shock from Costco over a seven-day period. It did clear the water and break down the Algae, afterwhich I immediately vacuumed the pool and cleaned the filter. While there is no visible algae in the pool, the water line in the skimmer has a ring of dark green junk that I wipe out daily with a paper towel.

Here are the results of my first testing using the K-2006 today.

FC - 2.5
CC - 3.5
PH -7.0
TA - 150
CH - 420
CYA - 0 (I guess, I couldn't see the black dot after about a half inch)

I'm confused about how much of what to punt in first; do I start by increasing the PH to 7.5?

Would appreciate any guidance.

[BigDave]

Tideman,
I'm going to guess that your CYA reading isn't right. Two reasons: You've been using tabs (trichlor) and you couldn't see the black dot, you have low CYA if you can still see the dot with the tube full.

I'm no expert but the people here that are and can help you will need to know what stuff the pool store had you put in the pool - chemical names not brand names.

I'll guess that you'll be advised to bring your clorine to shock level and keep it there until you have no more CC and you can maintain a FC level overnight. If your CYA is over a hundred you should probably consider a changing some of your water.

Good Luck!

[aylad]

Hello, Tideman, and welcome to the forum!!

Your first order of business should be to remove anymore trichlor pucks you have in the chlorinator. They do help feed chlorine into the pool, but they also drive pH down (probably why yours is so low but will probably come up on its own after switching to a different chlorine source) and drives CYA high. If you couldn't see the black dot after about 1/2 inch, then your CYA is well above 100, and possibly nearing 200, which is why you're having recurrent algae blooms. Where most people get into trouble with the chlorinators is that they don't understand that as CYA climbs, so must your baseline chlorine levels to make sure that algae doesn't grow. The chlorine level you must attain to reach "shock" level also climbs along with your CYA. IN short, the trichlor use has gotten your CYA out of control, which is causing your problems, so the trichlor needs to go, at least for the rest of this season.

So..you have a decision to make. With your CYA as high as it is, you're going to have to elevate your chlorine to the 25-30 ppm range and sustain that level for as long as it takes for the algae to truly die, as evidenced by clear water, combined chlorine less than 0.5, AND not losing any chlorine when measuring at sundown and again at sunup. This can take several days, and lots and LOTS of bleach. When you do finally get the algae defeated, you're going to have to run your pool at 8-12 ppm of chlorine ALL THE TIME to keep the algae from coming back. I don't know how much more swim time you have, or how feasible it is to drain/replace some water, but the pool will be much easier to clear up and maintain if you can drain/refill 50% or so of the water to bring that CYA down to a manageable level. THen your shock level that you must maintain to clear the algae and the minimum chlorine levels you have to maintain afterward will both be much lower and easier to manage. Just for a point of reference, in a pool your size, it's going to take about 7 1/2 gallons of 6% bleach to attain "shock" level, and will take about 1 quart to raise your chlorine by 1 ppm when calculating how much more to add each time to get back up to that 25 ppm level.

Your calcium level is very high, also--do you have high calcium in your fill water, or is it a result of using cal-hypo to shock? Doing a partial drain/refill will also help get that number down, if it's a result of cal-hypo use. It's high enough that any added calcium can create problems with milky water, which would eliminate cal-hypo as a chlorine source for you if you choose not to drain/refill some water.

Whether you choose to drain/refill or try to manage it the way it is, is up to you, and we'll be glad to help walk you through it, but either way I very very strongly recommend that you switch to bleach (or liquid chlorine, if it's available to you) for your chlorine source at least for the rest of this season. It will assist you in clearing up the pool, but not affect your pH like trichlor, or your CYA or CH like trichlor or cal-hypo will.

You can safely return the CYA to the store, if they'll take it back, as well as the baking soda, unless you'll use it otherwise around the house. (I would see if they'll trade it for liquid chlorine!!) Any CYA addition you need to make in future seasons can happen via your leftover trichlor, and the baking soda is used to raise alk--and yours is high enough.

Let us know what you decide, and we'll all go from there. Again, welcome to the forum, and congratulations on taking control of your own pool!!

Janet

[tideman]

Janet, thanks so much for the very detailed response. I shut the chlorinator off by setting it to zero. Unfortunately, I can't drain any water, as we are currently on water restrictions because of lack of rain, and our water usage is closely monitered. Therefore, large amounts of bleach is my only option for another month or so; I have 12 gallons of 6% on hand. Since I don't need the CYA, I should be able to exchange it for liquid chlorine.

Temperature is still in the mid to high 90's, we should have another six weeks or so before I cover the pool.

Calcium. Our subdivision has community well water managed by a local water company. I just received their annual report listing contaminants and constituents; the reports shows the calcium ppm is 108. And, of course, I did put in about 20 lbs of cal-hypo in the past week.

So, if I understand you earlier response correctly, I need to add 7.5 gals of bleach, monitor morning and evening, and add 1 quart of bleach as need to maintain a shock level of 25-30ppm until I no longer lose chlorine and CC is 0.5 or less.

I have four new filter cartdriges to change out, but I assume it is best for me wait until I get the algae under control.

Thanks much,

Jim

[aylad]

Just to clarify, you need to add 7.5 gallons of bleach, then test and add more at least 2-3 times daily,but as often as possible, to get back up to the 25-30 ppm range. The more consistent you are about keeping it above the 25 ppm level, the faster it will clear. If you let it yo-yo up and down, you're just wasting time, money, and bleach. When you figure out how many ppm you need to add to get back above 25, that's how many quarts of bleach you need--one quart will raise your Cl by 1 ppm. And yes, you need to keep it there until you're not losing any chlorine at night, the water is clear, and the CC is 0.5 or less.

Keep the pump running 24/7 while this is going on, and keep an eye on your filter pressure. You'll need to clean the cartridges as they gunk up with the dead algae. Brushing the pool daily will help, as well.

Good luck, and keep us posted on how it's going!!

Janet

[Watermom]

You say that you are on well water. Does the report show any metals in the water?

[tideman]

Thanks Janet, I appreciate your help and will keep you posted.


Watermom: Seems to be very minimal amounts of metals as follows:

aluminum - 0.029ppm
copper - 0.002
nickel - 0.003
iron - 0.034
zinc - 0.055

Jim