Pool Chemistry...

[Guest Mozeydozey]

I just set up a "prompt pool set" 13ft x 36" for the first time. Was told by a local supplier to put in 2 cups of "Buckman's Liquid Shock" and 2 cups of "Sun Alkalinity Plus". Waited two hours, and used "Pentair Pool and Spa Test Kit" according to it's instructions. Both levels were shown to have a 3.0 for Cl and 8.2 on the PH which are not accepable levels.. Now what do I do?

By the way, for a pool of it's rather small size, how does one come up with an approximate number in terms of gallons?

[Guest Suncrest]

Here is a formula for finding out the gallons of your pool.

To calculate the capacity of a pool:

1. Determine average depth of pool (in feet): (the depth at the shallow end + the depth at the deep end) / 2 = average depth.

2. Determine pool capacity.

Rectangle / Square Formula

Length (ft) x Width (ft) x Average Depth (ft) x 7.5 = approximate amount of gallons in the pool (the pool's capacity)

Pool Size 14 x 28 16 x 32 18 x 36 20 x 40

Approx. Gallons 13,230 17,230 24,300 30,000

Oval / Round Formula

Long Diameter x Short Diameter x Average Depth x 5.9 = approximate amount of gallons in the pool (the pool's capacity)

Pool Size 26 x 24 15 x 30 16 x 32 18 x 33 16 x 40

Approx. Gallons 10,000 12,000 13,500 15,500 30,000

Round Pool 16 feet 18 feet 21 feet 24 feet 28 feet

Approx. Gallons 6,000 7,500 10,000 13,500 18,000

* Sloping sides? If your pool has sloping sides, multiply your final figure by .85

[Guest poornima]

how to calculate the depth of pool

[waterbear]

how to calculate the depth of pool

If the pool has an even slope then measure the shallow and deep ends and divide by two. if it is not an even slope take depth measurements every few feet, add them together and divide by the number of measurements you took.

[waterbear]

I just set up a "prompt pool set" 13ft x 36" for the first time. Was told by a local supplier to put in 2 cups of "Buckman's Liquid Shock" and 2 cups of "Sun Alkalinity Plus". Waited two hours, and used "Pentair Pool and Spa Test Kit" according to it's instructions. Both levels were shown to have a 3.0 for Cl and 8.2 on the PH which are not accepable levels.. Now what do I do?

By the way, for a pool of it's rather small size, how does one come up with an approximate number in terms of gallons?

I know you are a newbie so I am going to simplify the answer for you. As to what you put in the pool (which is about 3000 gallons, BTW--acutally 2986 gallons if you have 3 feet of water in it, and would be just under 2500 gallons with 2.5 feet of water--2488 gallons, but calling it 3000 or 2500 is close enough for government work ) :

Liquid shock is another name for liquid chlorine, It comes in different strengths but even if it is the weak 6% (which by the way is EXACTLY the same thing as unscented ultra strength laundry bleach--sodium hypochlorite solution, 6%) you had a free chlorine level of about 3 ppm (actually if you had a full 3000 gallons of water in the pool your free chlorine should have been about 2.5 ppm)....which is excellent. However, since the chlorine is unstabilized and there is no stabilizer in the water you chlorine will get burned off by the sun very quickly.

Next, you put in an alkalinity increaser. A big secret that most pool stores don't want you to know is that alkalinity increaser is sodium bicarbnate, sometimes called sodium hydrogen carbonate--a different name for the same chemical. Most people know this chemical by it common name of baking soda. Yep, the suff that Arm and Hammer sells in the yellow box for a lot less money then the pool store sells it for! Now baking soda will cause the pH to rise to about 8.0-8.2 and, without knowing where your total alkalinity was before you added it I cant really say whether this was the right amount, too little, or too much. Your pool might be a small one but it is a real pool and needs to be cared for exactly as any other. The chemicals you need are:

a chlorine source (Laundry bleach is fine!)

pH adjusters (Muriatic acid and borax are what I would use, the are problems with using the pH incraser usually sold, which btw is just sodium carbonate, AKA washing soda found in the laundry aisle of the grocery store, same place you can find the 20 mule team borax!)

Alkainity increaser (baking soda)

Stabilzier (cyanuric acid)

Your pool is vinyl so you don't really need calcium so don't waste any money on this.

a GOOD drop based test kit (don't rely on strips) that will test for all these things. I recommend the Taylor K-2006 but the K-2005 is adequite but not as easy to use and is limited to how high it can measure chlorine levels (which can be an issue if you ever develop algae!)

ajust the Cyanuric acid to between 30-50 ppm

Keep the free chlorine between 3-5 ppm

Keep pH between 7.2-7.6 (you will find that you will have better pH stability if you shoot for the higher end of 7.6 in most cases)

Keep the total alkalinity between 80-100 ppm (if you decide to use trichlor pucks for chlorination you might do better keeping the alkalinity between 100-120 but you will need to keep close watch on the cyanuric acid levels since the pucks are about half cyanuric acid and if that gets too high your chlorine becomes much less effective and you might find that you are getting algae outbreaks! The only cure would be to drain and refill some of the water to get the CYA levels back down!)

Don't let this scare you off. It's really a lot easier then it sounds! The first step is getting a GOOD test kit (Your pentair 2 way tester only tests for Total chlorine (you have the yellow liquid test for chlorine). You want to be testing Free chlorine, which is why I recommend the Taylor K-2006 test kit, about $60. Also the pH test in your kit is likely to give you a false high rading on pH when the chlorine levels are high. This is a common interferernce to the pH test and has a lengthy chemical explanation I won't go into now (I've posted it many times before). The pH reagent in the Taylor kit has a chlorine neutralizer built in and is compensated to give accurate results for chlorine levels up to about 15 ppm. Most pH reagents aren't. (NO, I don't work for Taylor. We don't even sell their kits where I work! I wish we did! I just own a few different ones for my own use.)

Hope you find this info useful!