Does it matter where you take your water sample from?

Amail · Jul 24, 2015

I've plumbed a faucet into the backflush valve housing which allows me to take a water sample at the pump (when the pump is running) instead of crouching down at the pool. It's a convenience thing and easy on my back and knees.

I can't see why it would matter, but since I've never posed the question I might as well ask the brain trust: Is there any reason to suspect this isn't a good approach?

borjis · Jul 24, 2015

I'm not sure exactly if it is, but I do know it is mentioned often here to get your sample, from "1 foot below in the deep end."

so thats what I do.

YippeeSkippy · Jul 24, 2015

Regarding the OPs desire to save wear and tear on their knees and back- try using a piece of narrow PVC pipe (maybe 3' long or so) as a pipette to withdraw water from deeper down in the pool without bending over. Works a charm!

tim5055 · Jul 24, 2015

Just let the faucet run for a moment before you take the sample so any "dead" water that may be trapped in the faucet does not become the sample.

Now, this would not be a good idea if you have any chemical automation that may inject any chemical just before the faucet.

JoyfulNoise · Jul 24, 2015

It does to the extent that you want to get a sample of water from the bulk of the pool, not near the wall, not near a return and certainly below the surface by at least a foot.

My only concern with using the spigot at the equipment pad (I have one to right after the pump but before the filter), is that you can't be sure of the water sample you are getting. If the pump is drawing from the skimmer mainly, then that water is mostly surface water from the pool which could be low in FC due to sunlight degradation. If there are main drains involved, then that's a little better because the water is coming from both deep in the pool and at the surface but it would be hard to know what the proportions are. Obviously getting a sample from the deep end using a long draw tube like a straw (with your thumb initially held over the opening) lets you draw a deep water sample. But I also empathize with your back and knees as I have had past back issues and it is not fun at all.

So, you could try to take two samples of water, one from the pool and one from the spigot, and see if you can detect any differences. The biggest difference should be in the FC level as surface water will be depleted of FC from the sun. I would expect the pH to be fairly uniform. The TA might be noticeably different at the surface.

I'd be interested to see how your experiment turns out....good luck.

Sparkle · Jul 25, 2015

Taylor Technologies suggest "To get a representative sample, draw the water from mid-pool"

http://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=69

Amail · Jul 25, 2015

JoyfulNoise said:
It does to the extent that you want to get a sample of water from the bulk of the pool, not near the wall, not near a return and certainly below the surface by at least a foot.

My only concern with using the spigot at the equipment pad (I have one to right after the pump but before the filter), is that you can't be sure of the water sample you are getting. If the pump is drawing from the skimmer mainly, then that water is mostly surface water from the pool which could be low in FC due to sunlight degradation. If there are main drains involved, then that's a little better because the water is coming from both deep in the pool and at the surface but it would be hard to know what the proportions are. Obviously getting a sample from the deep end using a long draw tube like a straw (with your thumb initially held over the opening) lets you draw a deep water sample. But I also empathize with your back and knees as I have had past back issues and it is not fun at all.

So, you could try to take two samples of water, one from the pool and one from the spigot, and see if you can detect any differences. The biggest difference should be in the FC level as surface water will be depleted of FC from the sun. I would expect the pH to be fairly uniform. The TA might be noticeably different at the surface.

I'd be interested to see how your experiment turns out....good luck.

Water is drawing mostly from the barracuda, but some from the skimmer. Maybe 1/3 - 2/3 skimmer to barracuda. I don't have any chemical injection site (yet) and I make sure to purge any standing water before taking the sample.

I like your idea of taking two samples and comparing the results. Of course, seeing no difference doesn't mean there isn't a difference, but it's a data point.

JoyfulNoise · Jul 25, 2015

Amail said:
Water is drawing mostly from the barracuda, but some from the skimmer. Maybe 1/3 - 2/3 skimmer to barracuda. I don't have any chemical injection site (yet) and I make sure to purge any standing water before taking the sample.

I like your idea of taking two samples and comparing the results. Of course, seeing no difference doesn't mean there isn't a difference, but it's a data point.

That sounds ok. In my pool I have the skimmer tied to the main drain as one line coming in and the Kreepy Krawly vacuum on the other line with a 3-way valve setting the split between them. If I drew water from the spigot in my pump, I'd probably get a good mix of surface and deep water. I bet it would be very close to the water sample I get with my 4-ft draw tube. Perhaps I'll test that someday and see.

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