high CYA and phosphate reading

I just found this website and its great! thanks to everyone who contributes.

I have a inground plaster pool which is about 30,000 gallons, and a sand filter.

Here is my water analysis report that I got at a pool supply center today:

Total Chlorine 5.0
Free Chlorine 5.0
pH 7.4
Total Alkalinity 110
Calcium Hardness 500
Cyanuric Acid 150
Total Dissolved Solids 600
Phosphates 1000

The pool store talked me into buying a bottle of Sea Klear phosphate remover, but after reading some of these posts I am not sure if I should use it.

They said my chlorine levels were fine, but also after reading some posts it sounds like that I should have a higher chlorine level because of the high CYA of 150.

I am using stabilized chlorine tablets, which is probably why the cyanuric acid reading is so high.

Should I shock the pool tonight with calcium hypochlorite?

Should I be adding chlorine beach regularly in the evenings, in addition to the stabilized chlorine tablets, to keep a high chlorine level?

Any advice would be appreciated!!

Here is the best guess chart:

Stabilizer . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
=> 0 ppm . . . . . . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
=> 10 - 20 ppm . . . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
=> 30 - 50 ppm . . . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
=> 60 - 90 ppm . . . . 5 ppm . . . . . 10 ppm . . .. 20 ppm
=> 100 - 200 ppm . . . 8 ppm . . . . . 15 ppm . . .. 25 ppm

As you can see, with a cya of 150, you need a minimum of 8ppms of chlorine in your water. Since your calcium is also high, it is recommended to have between 200 & 400 in a plaster pool, I would do some partial drains and refills to get both numbers down. The only way to get rid of cya and calcium is to drain and refill. Bring your water down 1/3, and refill it back up. Test again and try to get your calcium and cya in better range. You can run a high cya pool, but you must keep your chlorine higher - if you keep the chlorine high enough you won't have any problems - you won't have to worry about phosphates. I wouldn't use cal hypo to shock - that's probably why your calcium is high. Just use regular bleach. Stop using the pucks, they add cya. So if you do some draining and refilling and switch to bleach, your water should stay clean and beautiful!

Thanks for your suggestions! I partially drained the pool yesterday and am re-filling it with fresh water.
I have an automatic chlorinator so would like to continue using the tri-chlor tablets that I recently bought at Costco. I live in Hawaii and a 3 quart bottle of 6% bleach is $2.50 at the supermarket! The pool stores here do not sell liquid bleach, only granular and tablets. So do you think it would be a good idea to use a combination of the tri-chlor tablets in the chlorinator, and then once a week (or should it be more often?) add a 3 quart bottle of 6% bleach to the pool ? It is about a 30,000 gallon pool.

The trichlor will continue to add CYA to the pool. The more it adds, the more chlorine you need, so you have to turn up the feeder, which adds more CYA. The only option is liquid chlorine or drain regularly to keep CYA down.

It sound like you live on Oahu as do we, on Waialae Iki near Kahala.

If so and your water supply is similar in composition to ours then the following levels should work, they work for us. It all depends on which Board of Water Supply wells are delivering your water.

pH 7.5-7.6 (Using Muriatic acid if you keep the below mentioned alkalinity there should not be too much out-gassing and you should not need to add acid too often or baking soda to increase the alkalinity. We add acid once a week to reduce by 0.2. Thanks to Chem Geek for this idea).

Alk 100 -90 (Use baking soda to increase it, we add 10 ppm every 10 days).

Calcium 200 (over 250 and the water on Oahu starts to become more demanding of acid and alkalinity. Do not ask me why).

CYA 50 to 55 (This should keep your liquid chlorine demand level down to a 1 ppm or 2 ppm demand per day. This depends on how the trades blow and how much dust gets blown into your pool. This would equate to approximately 50 oz of Wal-Marts 6% Ultra Bleach per day for a 1 ppm increase in a 30,000 gal pool. Higher levels of CYA over 55 make it very hard to get rid of bacteria quickly so are not recommended in this climate).

Chlorine 4-5 (We like 5, the pool sparkles more, at a CYA of 50-55. NEVER use anything other than PLAIN liquid bleach. Using pucks is feasible but not recommended as they add CYA and Calcium and you will spend money draining and refilling. Keep leaves and debris out of your baskets daily and backwashing your filter as needed will help reduce the chlorine demand to 1 ppm or 2 ppm per day).

Three things to remember with liquid chlorine, if you pour it into the pool in daylight it will immediately lose some of it strength say 6% to 5%, you will need more, so pour it around the pool after dark, or if you prefer pour it close to the return jet (after dark) while the pump is on. If you are going to continue to use your pucks NEVER pour it into the intake basket as it could cause an explosion in your automatic chlorinator, when it hits the pucks. Finally NEVER pour it into the automatic chlorinator to let that distribute it as it could potentially explode, even if you have no pucks in it.

As regards Phosphates you can ignore the level if you have no or very little nitrates. Nitrates are normally introduced by leaves, algae growing on the roof running off into the pool , composite shingles draining into the pool, and wind born fertilizers. If you do have nitrates it is best to drain as there is no easy way to get the levels down. You can purchase aquarium test strips from the pet store and these should let you know what your nitrate level is. Phosphate remover is therefore essentially a waste of money, I know I used it. Try to keep fertilizer away from the pool this is the biggest culprit. Also if your roof runoff water falls into your pool this too can create nitrates so put in gutters if you do not have any.

If you are getting stains these are caused, in all probabilty, by the wind-born volcanic dust (red dirt aka ferric oxide aka rust). Adding a little metal out treatment weekly will help keep these stains down, be aware however that most contain phosphates so you will get a high reading. Not a problem if you have no or low nitrates. Removing stains is a whole other subject, see MBAR on this she is the expert.

Not knowing how long it has been since you drained your pool the following may not apply. A few weeks ago I helped my neighbour get rid of their stains, using the Ascorbic Acid treatment method. The pool had a CYA of 150 and spent three weeks getting all the other numbers right before draining it . When we were three quarters of the way down this pool smelt like rotten anchovies so I am glad we drained to empty. My guess is that no amount of chlorine was going to get rid of some bacteria. Once the pool was 90% drained we acid washed it, to get rid of persistent, hardly noticeable, very light algae on the pool walls, cutting the acid 1 to 4, and putting large amounts of soda ash in the bottom of the pool to neutralize it. The pool looks like brand new and it is 16 years old, prior to this it looked like a mud bath.

Hope this helps.


Aloha

thanks for taking the time to post your informative reply!
we live in Kailua so it is nice to get advice from someone who also lives on Oahu.

Vivian