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    Pool Chemistry for Inground Vinyl Pools

    August 19, 2013


    Each type of pool (concrete, vinyl, fiberglass, tile) has slightly unique differences when it comes to water balance and the process of maintaining the water chemistry of the pool. Here's a look at water balance for a vinyl liner pool.


    water-balance-wheel-4A lot of people call and ask what does water balance actually mean. Water balance is very important to maintaining your pool as well as keeping the water safe for your swimmers. Balancing your pool means to make sure your pH, Alkalinity and Calcium Hardness are at the levels they are supposed to be.

    If the water is not balanced, you can slowly ruin a vinyl pool liner. The liner can bleach, wrinkles begin to appear, stains and discoloration can start appearing on the liner and calcium deposits can form on the pool liner. Swimmer's skin can become irritated, as well as their eyes.

    Some of things affect your water balance are the weather, swimmer load, suntan oils, dirt and leaves. Every time the wind blows, your water changes, constantly. This is why it is so important to check your water at least twice a week. You will need to test and balance the pH, Alkalinity and Calcium Hardness.test-kits

    Do not use a cheap-o pool test kit to try to balance your water. Use 7-way test strips or a 5-way test kit that checks for everything. Or, we have this 4-way test kit that can also do the job. I would also suggest having your local pool store test it every now and then.

    Finally, only add one adjustment chemical at a time unless instructions tell you otherwise. Allow the first chemical to circulate and dissolve well before adding another chemical.


    water-balance-wheel2I would start with the Alkalinity first. The alkalinity should be between 90-120 ppm for a vinyl liner pool. Next, I would adjust the pH. The pH should be between 7.4-7.6. Last you would want to test your Calcium Hardness. The calcium hardness should be between 200 - 400 ppm.

    Alkalinity is the buffering capacity of your pool water, and helps to keep your pH stable. do not allow your alkalinity to drop below 90 ppm. If the alkalinity is to low for long periods of time, the liner will begin to wrinkle and pucker, and you will have problems controlling the pH, creating a possibly acidic environment - not good for vinyl.

    When calcium hardness is low in a swimming pool, it will try to extract calcium from the pool walls. This is more evident in a concrete/gunite pool, as it pulls calcium from the plaster.  In a vinyl liner pool where there is not enough calcium, it cannot pull calcium from the liner, but it saps the flexibility of the vinyl. If the calcium hardness level is too low for a long period of time the liner will become very brittle, and you may begin to see tiny holes in the liner.


    When you have a vinyl liner pool, you want to test for minerals in the water. If you have minerals in your water, especially well water, they can stain a vinyl liner pool. it is easier to try to prevent the minerals from staining the pool liner or the pool steps, than it is to remove them.

    We have products like Metal Free which will lock up these metals, keeping the liner stain free. If you already have stains on your liner, we have a few products that will remove most stains, and there is also a pool stain test kit that can identify the stain and tell you how to treat it.


    Most chemicals need to be dissolved or they could stain a pool liner. Reading the package instructions is extremely important, and please never mix chemicals.use pool chlorinators

    Chlorine tablets should never be put into a skimmer or a floater on a vinyl pool, as they could harm the vinyl. Use a Chlorinator mounted by the equipment. Salt Chlorinators are very nice used with vinyl pools, and most users find the softer water to be better for their liner.

    When shocking or super-chlorinating the pool, always pre-dissolve the powder in a bucket of water, to prevent any of the undissolved granules from falling to the pool liner. Be sure to pour the powder into a bucket filled with water, not the other way around. This is to prevent a possibly explosive reaction.chlorine-free-shock

    It's recommended with vinyl liners to shock only as needed, and to only the level needed. Needlessly high levels of chlorine are corrosive and slowly bleach or weaken the vinyl. For this reason, my final recommendation is to use a non-chlorine shock with vinyl pools.  

    Debbie Farnan
    SPP Pool Expert  

    Blog Author
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