How to Properly Take a Water Sample.
I admit- This isn't going to be the sexiest blog, or even in the top 10 of interesting blogs. But this is extremely important, as testing your pool water is the foundation of your swimming pool season success. Staying on top of your water chemistry readings helps fend off any potential headaches related to pH/alkalinity/sanitizer imbalance. But most pool owners do not know how to properly take a water sample for water testing.
This is a big deal: A sample is supposed to reflect your entire pool in terms of water chemistry. If a sample is tainted or otherwise amiss, you can create big headaches and spend a bunch of money needlessly. Nobody wants that. So lets make sure you're collecting water properly for either your home test or for testing at your local pool store...
If you're conducting a test poolside, most people fill the 4-in-1 test bottles directly. Make sure you splash and rinse out the tester prior to collecting your sample to eliminate possible contamination. Repeat this process between pH, alkalinity, and chlorine tests.
Most pool companies require at least 8oz. of water for pool water testing. If your local pool store does not offer a free sample bottle (or you lost/forgot yours) use a container that not only meets their volume requirements, but is free of contaminants: Be sure to thoroughly rinse anything being re-purposed and never use pickle jars, as the vinegar and salt will never fully be washed out. Also- Never use an empty chemical bottle as that may skew your sample.
Where to Take the Test?
If possible it is always preferred to take a sample from 18" below the surface. As that isn't always possible, try to take it from as deep as you can and not directly from the surface. There is more churn below the surface and less contaminants present that may effect your sample.
Collect water away from return jets. As most swimming pools are equipped with salt systems or automatic chlorinators, the water coming directly from the return jet will have higher salt and chlorine levels (and potentially higher pH levels).
If your pool has different depths, take the water sample in the deep end as it will be less effected by the water temperature.
When to Take the Test?
This is another overlooked aspect of water testing: Timing. Don't take a water sample if you've added chemicals to your pool in the last 12-48 hours. There are many caveats to that large of a time discrepancy: How many gallons is your pool? What chemicals did you add? What were you trying to accomplish when you were adding chemicals? So on so forth. Most pool professionals will be able to tell you when to retest your water based on your specific circumstances.
Possibly the biggest cause of pool water sample inaccuracy is rain. If it is raining, do not test your water. Rain is very low in both pH and alkalinity. When its raining, the top layer of your pool water- the origin of your water sample- will not accurately reflect the pool as a whole until the rain water has mixed in completely with the rest of the water.
If it just rained, or will threaten to rain in the very near future, wait at least 8 hours before conducting a test or gathering a sample for testing.
What to do After the Sample is Taken?
The fresher the better is the name of the game. Taking the sample in the morning and going to work, running errands, etc. is not ideal. If the sample sits in your cubicle all day or in your car the sample could become tainted. Additionally- If you take a sample in the morning and it rains, the sample is no longer accurately reflecting the current state of your pool.
If you're new to all of this, make sure you have the basic information available for your local pool store: Pool size (gallons), type (concrete, fiberglass, liner), sanitizer (salt system and type, automatic chlorinator, etc), and what has been done to the pool in the last 48 hours.
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