As you learn the basics of pool ownership and management, you will be introduced to terms you may be unfamiliar with. It is important to learn what these mean and you pick up a lot of the knowledge you need over time and with experience. One of the things most pool owners soon realize is that a lot more goes into having a pool than skimming leaves off the top and taking a daily dip. Pools can be finicky and even with proper care, they will experience issues from time to time. Sometimes that is a problem with chemical balance, whereas other times it is a problem with the build-up of a particular substance in the pool water.
One such substance that can build up in the water over time is what is called a phosphate. What’s phosphate?
Phosphate is a chemical compound that has phosphorus in it. When water runs over rocks, wood, and other materials, it will leech off small traces of a variety of minerals, taking up phosphorus in the process. While on its own it is harmless, it can cause a lot of problems in your pool.
How Phosphates Get in Your Pool Water
Phosphates do not break down on their own. This means that they will accumulate in water over time and it is this accumulation that can cause issues for pool owners. The water you use to fill your pool is likely to contain a small number of phosphates and this is not an issue. The issue is the accumulation of phosphates over time and there are a lot of ways this can happen.
Phosphates are found in a lot of different places. Residue on the skin or in your hair may contain phosphates that will become dissolved into the water while you swim. Rotting leaves contain phosphates and even after they are skimmed off the pool water, they may leave phosphates behind.
Many agricultural chemicals, including fertilizer, also contain phosphates, so if you fertilize your yard and walk through it before getting in the pool, you are likely to bring more phosphates in the process.
Since it is so ubiquitous, it is impossible to remove all phosphates from your water and in small amounts, they cause no issues. The problem is when the levels of phosphates in your pool reaches over 1,000/ppb.
Do I Need to Remove Phosphate?
As we noted above, you don’t want your phosphate levels to get over 1,000/ppb. So the answer to whether you need to remove phosphate from your water is, as usual: it depends. If your phosphate levels are below this amount, you are probably okay for the time being and don’t need to do anything to address the issue. This, again, helps to reiterate the vital importance of regular water testing. Regularly testing your water will alert you to any problems that may be brewing, including the increased accumulation of phosphates in the water.
The problem with phosphates is that they can serve as food to other nasties you most definitely do not want in your pool, such as algae. It is a short jump from just a bit of algae in the water to a literal algae bloom, which is a frustrating problem to have to deal with. It is important to remember that there will always be phosphate in your water. No matter what you do, a little will be present and in small doses, it isn’t a problem. It is when the levels of phosphates in the water exceed 1,000/ppb that the potential for algal blooms and other issues might arise.
A note about water testing for phosphates
Unless you have a fancy or professional water testing kit, chances are the one you have does not test for phosphates. You can easily find inexpensive phosphate test strips online or at your local pool supply store.
Some people simply take a sample of their pool water to the local pool supply store a couple of times a season for testing. Pool supply stores have much more detailed testing systems that will allow them to give you detailed information about the current state of your water.
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Removing Phosphates by Draining Water
If you test your water and find that your phosphate levels are more than 1,000/ppb, you will want to remedy the problem. The easiest way to remove phosphates from your pool is to do a partial drain. Draining about a quarter of your pool’s water and refilling it with fresh water is often enough to dilute the phosphates to a more manageable level.
For draining, you can go with a few different techniques:
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Attach a hose to the drain valve on your pool and drain it to the street or sewer.
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Siphon the pool water using a standard garden hose or garden hose with primer pump
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Drain the pool using a submersible pump, AKA a sump pump
Why You Shouldn’t Use Products Designed to Remove Phosphates
There are products on the market that claim they can remove phosphates, but most professional pool techs advise against using these products. The thing is, not only are phosphate removers simply not necessary, many of them are toxic. Phosphate removers are most often made from lanthanum, which is what is called a rare earth element. Recent studies have shown that this substance is moderately toxic, whereas, despite their issues, phosphates are not.
Phosphate removers can also reduce the effectiveness of other pool chemicals. If, for example, you have high levels of metal in your pool water, you may be using a product called a metal sequestrant. Most of these products are phosphate-based, so if you use these in tandem with a phosphate remover, well, naturally, you are going to render that ineffective. If you have a saltwater pool, it is highly advised that you not use phosphate removers. There is a lot of debate and controversy at this point, but there is a lot of evidence to support the claim that phosphate removers can damage your salt cell, which is an expensive element to have to replace.
Keeping up with regular pool cleaning and maintenance is your best weapon against excessive accumulation of phosphates. Regularly using chlorine to shock your pool is a recommended part of basic pool care and can also help to reduce the likelihood of your having a phosphate build-up.
How to Reduce Future Phosphates in your Pool
Oftentimes, making sure to regularly skim your pool water, brush the surfaces, and make sure that your filter is free from clogs is enough to not only keep phosphates from accumulating but to address the problem should it arise.