How to Test for Phosphate in Water

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Phosphate is a contaminant that’s commonly added to municipal tap water to prevent the leaching of lead and copper from water service lines.

There’s little scientific evidence to confirm any of the possible health effects of phosphate in drinking water, but we do know that phosphates have a significant impact on our ecosystems, and may promote the growth of microorganisms in water.

Our water treatment specialists set out to try all the testing methods for phosphate in water currently available, and we’ve shared our top recommendations in this guide.

How to test for phosphate in water

🚰 Get a Water Sample Tested by a Certified Laboratory

The best way to understand how phosphorus affects your water quality is to use a certified laboratory testing method.

Our recommended certified lab is Tap Score by SimpleLab. The Essential Hydroponics Water Test tests for hydroponics nutrients, including phosphorus.

Lab testing uses the most comprehensive water testing methods and provides the most accurate results. If you want to know precisely how much phosphate your water contains, you should use a lab test.

Most laboratories will mail you a sample-taking kit, which you can use to take your water samples, then post your samples back to the lab for in-house testing.

Here’s an overview of the sample-taking process for laboratory phosphate testing:

  1. Choose your preferred phosphate water test and order the sample kit.
  2. Wait for the kit to be delivered to your home.
  3. Unbox the kit and put on the disposable gloves (if provided).
  4. Follow the instructions in the kit to take an untreated sample of your tap water in the included vial.
  5. Put the lid on the vial, return it to the box, and fill out the sample information.
  6. Send the sample back to the laboratory.
  7. Wait to receive your test results (usually via email).

Good to Know: The turnaround time for a lab test depends on shipping and the lab’s processes, but most labs should get your results back to you within 5 days.

As well as telling you what your water contains, the best water testing laboratories should provide you with a health-risk assessment for your water quality, treatment recommendations, and an overview of any potential aesthetic and plumbing issues. You might also learn whether or not your water’s phosphate is organic (associated with organic material) or inorganic.

Water test

πŸ§ͺ Use a DIY Phosphate Test Kit

Phosphorus can create a harmful environment in aquariums and fish tanks by altering the chemistry of water. It can also contribute to algae production, resulting in oxygen starvation.

This is likely unimportant to you – but it does mean that there are plenty of phosphorus test kits available online for fish keepers and home aquarium owners.

You can use a DIY water testing kit to test your drinking water quality and get a reading of phosphate in PPB (parts per billion). Phosphate test kits are widely available online and generally cost within the $10-$20 range.

This form of testing is less accurate, and won’t give an exact reading. However, it can be a good place to start if you don’t know whether or not your water is contaminated with phosphorus.

There are a few different phosphate test kits using different standard methods of testing, including kits that use test strips, and kits that use a liquid reagent.

Here’s how to use a DIY phosphate test kit with testing strips to analyze your water for this contaminant:

  1. Buy your chosen at-home phosphate testing kit. You could go for a test that exclusively detects phosphate or a test kit that also detects other common tap water contaminants.
  2. Unpackage the test and wash your hands.
  3. Take a sample of your water in a clean glass.
  4. Dip a test strip into your tap water and wait for it to change color.
  5. Use the color chart in your kit to determine how much phosphate your water contains.

Here’s how to use a DIY phosphate test kit with a reagent:

  1. Buy your chosen test.
  2. Unpackage the test and wash your hands.
  3. Fill the included test tube or container with your water sample.
  4. Follow the instructions in the test to add the reagent to your water. Ammonium hepamolybdate, ascorbic acid, and stannous chloride are common liquid reagents used for phosphate testing.
  5. Wait for the water to change color (this happens when phosphate reacts with the reagent).
  6. Compare the color of your treated sample to the color chart to get a reading of its phosphate level.

Good to Know: A typical DIY phosphate test kit can detect phosphate levels in ranges, usually from 0 to 1,000 PPB. So, for example, the color shade of your test strip may indicate that your water contains 100-200 PPB of phosphate, or 300-500 PPB, or 500-1000 PPB. The exact ranges depend on the test you’re using.

Phosphorus test

πŸ“ Interpreting Your Results

Once you’ve used a test to measure phosphate in your water, you can decide if – and how – to take action.

Low concentrations of phosphate in water aren’t thought to have any health effects, and the EPA doesn’t currently regulate phosphates in tap water – it only recommends that total phosphorus in streams shouldn’t exceed 0.1 mg/L, and that total phosphates (as phosphorus) in streams that enter a lake or reservoir shouldn’t exceed 0.05 mg/L.

That doesn’t mean that phosphate is definitely safe in water; but it’s highly unlikely to be present in high concentrations, and there is currently little evidence to suggest that this contaminant poses a human health risk. In fact, on the contrary – humans need phosphates for energy, pH maintenance, the metabolism of calcium and vitamin D, and more.

However, too much of anything can be dangerous. If your water contains an unusually high phosphate concentration, you may want to reduce phosphate with a water treatment system.

There are a few water filters that are effective for phosphorus removal:

Reverse osmosis system and distiller

πŸ“‘ Final Word

We wrote this guide for people looking to measure phosphate levels in their drinking water. We hope we’ve been able to provide the answers you were looking for here, but if you have any further questions, our comments are open below.

To summarize, phosphate test kits are the best option for quickly determining whether or not your water contains phosphates, while laboratory water tests provide a more detailed and accurate result.

You can look into methods of phosphorus removal if your water contains elevated levels of this impurity.

  • Jennifer Byrd
    Water Treatment Specialist

    For 20+ years, Jennifer has championed clean water. From navigating operations to leading sales, she's tackled diverse industry challenges. Now, at Redbird Water, she crafts personalized solutions for homes, businesses, and factories. A past Chamber President and industry advocate, Jennifer leverages her expertise in cutting-edge filtration and custom design to transform water concerns into crystal-clear solutions.

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