Sampling water before pump can be started

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NorthernHAM

Well-known member
Apr 3, 2021
53
Northern Ontario, Canada
Pool Size
8000
Surface
Vinyl
Chlorine
Liquid Chlorine
Hey friends,

I bought a home with a pool that has been maintained with trichlor and cal hypo since 2006. I would like to test my water soon, even though I will only be officially opening sometime in May. My cover is off and the water is crystal clear and 54 F, and I'm super excited to open it (it's been an insanely nice spring thus far, but I'm sure we will get a surprise snowfall at some point soon.)

Because the water was only drained to a few inches below the skimmer line, I am worried about the CYA and CH levels. The plumbing isn't hooked back up yet and of course the pump cannot run at the current water level so I know I won't be able to take a representative sample. Is there a way to mix up the water efficiently enough to be able to take a sample? Would brushing the walls down be enough to mix up the water? Or manually vacuuming without actually vacuuming (no pump to form the suction)?

If the CYA and CH are off the charts like I anticipate them to be, I would rather drain the required amount of water prior to topping it up, which seems like it would be a non-required waste of water. But in order to figure out what kind of drainage I would need, I need to test.

The good news is that I received my K2006C test kit yesterday, even though it was supposed to take 3 more weeks!! *happy dance
The bad news, albeit slightly unrelated, the LC I thought I could buy @ $0.20/oz is from a company that only supplies a different company in my town, and therefore doesn't offer the refill price. Now the best price I can find is $0.37/oz... *sad dance

Thanks in advance! Haley
 

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NorthernHAM said:
The bad news, albeit slightly unrelated, the LC I thought I could buy @ $0.20/oz is from a company that only supplies a different company in my town, and therefore doesn't offer the refill price. Now the best price I can find is $0.37/oz... *sad dance

Thanks in advance! Haley
Click to expand...

Is that $0.20/oz supposed to be $0.02/oz? $0.20/oz would work out to $25.60/gallon (128oz). :eek: I usually pay $3.99/gallon so curious if prices are really that much higher in Canada.
 
magiteck said:
Is that $0.20/oz supposed to be $0.02/oz? $0.20/oz would work out to $25.60/gallon (128oz). :eek: I usually pay $3.99/gallon so curious if prices are really that much higher in Canada.
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I'm using the calculator on pool math, which standardizes it to 100% chlorine!

The cheap one I don't actually have access to is a 10 L (2.64 gal) of 12%, which is $7.91 after tax. That would equal $2.99/gallon of 12%.

The one I do have access to is a 5L (1.32 gal) jug of 10.8% for $7.67. $0.37/oz standardized to 100% bleach, or $5.81/gallon for 10.8%.

Also, if we are comparing, let's not forget the CAD:USD conversion rate. Your $4/gallon would be my $5.
 
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NorthernHAM said:
Because the water was only drained to a few inches below the skimmer line, I am worried about the CYA and CH levels. The plumbing isn't hooked back up yet and of course the pump cannot run at the current water level so I know I won't be able to take a representative sample.
Click to expand...

I don't think not running the pump will have a major impact on testing water unless you recently added anything. It can have an impact on the FC test or pH, as FC might get used up faster in some areas of the pool than in others. But if calcium and CYA have been mixed in for a long time, then not running the pump before testing shouldn't have an effect on the test results.
 
mgtfp.. I'm not going to disagree with you, but I am going to offer an alternative theory...

'HAM, Is that 54F at the top or the bottom of the water column? You live up north and you are coming off winter, so there is a chance the pool has a some temp stratification.. its colder at the bottom. And with that there may be an uneven distribution of chems in the water. But you don't have a very deep pool and it has a flat bottom, so you should be able to mix it with some good brushing. If you can take a temp at the bottom water you could tell if you have a mini thermocline.

Here's why I think a mini thermocline can happen... cause it happened to me. A few springs ago my pump died and during the wait for my replacement motor I was diligently chlorinating with liquid CL.. I could see it sink to the bottom when I poured it in and I swept as much as I could to mix it... apparently it wasn't enough. I tested my water, 18" below the surface and I could see I needed chlorine, but I don't think I was testing deep enough. When I finally got the pump back on my FC spiked, and I hadn't even added any chlorine. And it was still to cold for the SWG to do much of anything. So I figure that the chlorine had been settling in the colder water at the bottom until I got the pumps running and things really mixed. My deep end is all of about 6.5ft and the water temps were in the low 50's at the time. I have been curious to try and recreate it and see if I can test the bottom water from the top water to see how much of a temp difference there was. Its the oceanographer in me.
 
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Interesting observation, mguzzy, makes sense. I guess in the same way it could happen that you lost chlorine at the bottom of the pool (let's say because the bottom was for some reason algae infested), and the chlorine in the bottom layer dropped to zero. But because the colder, denser, water from the bottom layers stays at the bottom, you might not notice that FC dropped to zero down there by testing water from the top layer - kind of the opposite of your example.

But both are examples where a parameter (FC) changed drastically, and because of a lack of mixing the change didn't reach all areas of the pool.

In case of parameters that change only very slowly like CYA and CH, I would assume that a lack of mixing won't have too much effect. But if there was a lot of dilution with rain water that's warmer than the current pool temperature, the pool might get diluted inhomogeneously.

I guess, mixing the water with the brush or the leaf rake before testing wouldn't hurt to be on the safe side.
 
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Right.. the influx of rain and snow melt water is going to be a different density.. Colder water is heavier. And so it will stratify based on its relative temperature in the absence of any mixing from the pump action. Its the whole concept behind an in place water exchange.. pulling from the bottom or the top depending on the temperatures of the two water sources. Add salinity from a SWG pool, and you add a halocline to the mix. But if I recall from past posts you have a background in physics.. so I am preaching to the choir.

And to the OP.. get a really BIG spoon and mix it.
 
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I too saw an unlikely unmixed pool every spring. The majority of the rain water was from plenty of time before the first test and should have been well mixed / equalized. But the top foot or so would test much closer to rain, and upon running the pump for the first time, it tested much more ‘pool-like’ (although still low from all the dillition).

I understand this is difficult to recreate outside of a lab, but for 7 seasons I saw it with my own eyes. Maybe due to a large temp change of the 60/70 degree early spring rain and the 40/50 degree pool water ??? I dunno. 🤷‍♂️
 
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mguzzy said:
mgtfp.. I'm not going to disagree with you, but I am going to offer an alternative theory...

'HAM, Is that 54F at the top or the bottom of the water column? You live up north and you are coming off winter, so there is a chance the pool has a some temp stratification.. its colder at the bottom. And with that there may be an uneven distribution of chems in the water. But you don't have a very deep pool and it has a flat bottom, so you should be able to mix it with some good brushing. If you can take a temp at the bottom water you could tell if you have a mini thermocline.

Here's why I think a mini thermocline can happen... cause it happened to me. A few springs ago my pump died and during the wait for my replacement motor I was diligently chlorinating with liquid CL.. I could see it sink to the bottom when I poured it in and I swept as much as I could to mix it... apparently it wasn't enough. I tested my water, 18" below the surface and I could see I needed chlorine, but I don't think I was testing deep enough. When I finally got the pump back on my FC spiked, and I hadn't even added any chlorine. And it was still to cold for the SWG to do much of anything. So I figure that the chlorine had been settling in the colder water at the bottom until I got the pumps running and things really mixed. My deep end is all of about 6.5ft and the water temps were in the low 50's at the time. I have been curious to try and recreate it and see if I can test the bottom water from the top water to see how much of a temp difference there was. Its the oceanographer in me.
Click to expand...
I think this exact thing happened to me this year, and I'm embarrassed that I didn't realize it because I used to work in a limnology lab studying a pair of local meromictic lakes.

I did brush a bunch before testing and after adding chemicals, and even ran the robot, but that wasn't enough to turn the water over.
 

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NorthernHAM said:
At least I will get an idea, and be able to learn how to use my kit :)
Click to expand...

To get even more practice runs with your kit you could take a sample from the top and one from the bottom layer of the pool. If the test results are close to each other, you are good to go. If they are too different, then stir your tea for a bit longer.

That's how you can take a sample from further down without getting wet:

Dirk said:
If you ever want to take a break from your cold water acclimation training, build yourself one of these. It's a couple feet of 3/4" PVC with a cap on each end. Drill a 3/8" hole in each cap. The trick is to hold your thumb over the top hole before you dip the pipe into the water. Release the hole when the pipe is at depth (about 18") and the pipe will fill with 18" deep water. Put your thumb back over the hole and pull the pipe back out. Fill your sample container. Do it twice. The first time use the pool water to rinse your sample container. Which rinses the pipe with pool water at the same time. Then dip again and use the second sample for your testing. At most you'll get your fingertips wet, and you can do it without kneeling or even squatting.

View attachment 176146View attachment 176148
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Or use a bit of garden hose and do the thumb thing.

For the CYA test it is important to let a cold water sample warm up to room temperature before running the test. The other tests can be done straight away (pH should actually be tested straight away because pH is higher in colder water, if you let the sample warm up first, you'll get a false reading that's a bit too low.).
 
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mgtfp said:
For the CYA test it is important to let a cold water sample warm up to room temperature before running the test. The other tests can be done straight away (pH should actually be tested straight away because pH is higher in colder water, if you let the sample warm up first, you'll get a false reading that's a bit too low.).
Click to expand...
Good call!

New plan: sample top and bottom, measure pH immediately and take the temperature, warm sample up for CYA; then brush it all up and do it all again

mguzzy said:
I use a water squirter.. the kind you get at a dollar store.. looks like a 3 ft long turkey plunger!
Click to expand...
I have absolutely no idea what you're talking about, but now I want to find one! To bad all of our dollar stores are closed at the moment... siphoning out with a hose it is!
 
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