I'm doing ok... but I could be doing better (in terms of managing my CSI between summer & winter); how about you?

[Gary Davis]

Are you ever successful in balancing the Calcium Saturation Index without having to adjust the alkalinity and/or calcium saturation by a large amount?

<----- aggressive ------ 0 ------ scaling ------>​

I'm doing ok... but I could be doing better (in terms of managing my CSI between summer & winter).

1. The water temperature fluctuates wildly between summer and winter of course
2. Its pH remains generally on the high end of the pH ceiling (around 7.8 or 7.9), and there aren't any water features to gas off the CO2
3. The Total Alkalinity is adjusted with muriatic acid to about 100 ppm in general
4. I adjust Calcium hardness to somewhere around 3 times the TA, in general, using Snow Joe pellets
5. CYA is kept low on purpose, at around 30 ppm, to keep the FC needs lower
6. TDS is around 500 ppm (extremely low bather load and it's not a SWCG pool)
7. Borates/Phosphates/Iron/all-that-other-stuff is 0
8. Free Chlorine is always kept at least 7.5% of the CYA level
9. Combined Chlorine is generally less than 0.5 ppm
10. The pool is in-ground, plaster, with a tile waterline, no heater, no cover, no shade

Given those numbers, which of course fluctuate over time (see large unavoidable dilution factors below), the CSI is in the ~0 to ~0.25 range most of the time.
With that as a background, my question is one of how well you are managing your CSI index between summer and winter conditions.

There's probably no factual answer to this question, only anecdotal happenstance for each one of us, but I still am curious if anyone is more successful than I am at arriving at a balance that isn't constantly changing in terms of how I need to adjust the alkalinity and/or calcium saturation levels.

In California, during the summer my water is about 70 to 85 degrees most of the time where there is evaporation which causes me to have to add high alkalinity (180 ppm) and low calcium (180 ppm) well water to top off the pool to the skimmer levels; in winter the water is around 40 to 55 degrees most of the time where the monsoon rains cause high acid zero alkalinity (0 ppm TA) and zero calcium (0 ppm CH) to be added to the uncovered pool (to the point it overflows out the drainage holes).

I don't chase the pH other than to use HASA muriatic acid to lower the well-water-fill alkalinity to around 100 ppm, and I don't modify the CYA as I use HASA liquid chlorine at a level at least 7.5% of the FC level given my summer CYA is about 30 ppm (winter CYA drops to around 20 ppm due to the rain dilution combined with me getting lazy since the sun is at a lower angle and the daylight hours are lower and temps are lower so the CYA isn't as critical to manage).

What's singular about California is there is always literally zero rain from about early March to about early December, and then we have the unpredictable rainy season - where it can be a drought - in which case we have almost no rain - or - we have sporadic monsoons from about December to March - so there are really two seasons in terms of water that is added, the summer being predictable at no water, and the winter being unpredictable at from low water to monsoon levels.

• Summer = 180 ppm TA & 180 ppm CH well water
• Winter = 0 ppm TA & 0 ppm heavy rain water (or not)

In addition to the huge temperature fluctuations, it's these unpredictable winter condition water additions that affect my CSI calculations the most, I think.

I'm well aware the factors that go into the CSI calculation, which, mostly are temperature and pH and carbonate alkalinity, but also to a lesser extent CH, CYA, TDS, and borate levels, where, for me, in terms of summer and winter fluctuations, the two factors most affecting my CSI seem to be

1. Temperature
2. Diluent (either well water or rain water, depending on the season)

Given all that, what I'm wondering, from those who have TRIED to maintain balance, is how well have you succeeded, given that the temperature & the diluent messes up any one setting you may have aimed for.

Of course I'm aware there is an AGGRESSIVE:OK:GREAT:OK:SCALING range, with there being a wide "OK" range on either side of GREAT, which means we don't have to be at exactly a 0.0 CSI, but still - I'm finding, essentially, the following:

• Summer = I have to lower the calcium levels to get closer to a 0 CSI
• Winter = I have to raise the calcium levels to get closer to a 0 CSI

Luckily, since I don't chase pH, it's mainly my temperature that fluctuates (the pool is not heated) but, as you are aware, the temperature is the major CSI factor.
Also luckily, I'm happier to be on the positive CSI range (scaling) than the negative (aggressive) for my plaster pool, especially as I don't have SWCG equipment.

Even luckier, I guess, is that many people just ignore CSI and concentrate only on chasing ranges (not me, but I understand many people do that).
The reason for this question is simply to learn how others handle the different CSI conditions between summer and winter, as outlined above.

In the end, I'm doing ok, but I could be doing better in terms of finding a happy medium of calcium hardness & carbonate alkalinity between summer and winter.
How about you?

 

[mgtfp]

My opinion is, that at the point where CH gets actively decreased in summer, and then increased again in winter, the line towards micromanaging has been well and truly crossed.

You don't have a SWG, it should be easy to balance your water in a way where CSI is slightly negative in winter and maybe slightly positive in summer. Don't chase zero, it's a cat chasing its tail. Even if CSI is closer to -0.6 over a few weeks or even months in winter, this will not have any noticeable impact on a plaster surface. CSI just tells you how close to equilibrium you are. The dynamics, how fast the system is working towards equilibrium, is hugely temperature dependent. Low temperatures slow reactions down.

Think of descaling a water kettle. Put some vinegar in the kettle und put the thing in the fridge. It will take ages for the vinegar to dissolve the scale, it might never happen. Turn the kettle on and bring the vinegar to the boil, and the scale will be gone in less than a minute - even though you actually increased the CSI of the vinegar solution by heating it up.

If simply maintaining pH slightly higher over winter is not sufficient, then play with TA, say 80 in summer and 100 in winter, or something like that. These are easily adjustable parameters. But don't fiddle with CH.

 

[Gary Davis]

There is a really good current thread which is highly related to my questions

• Winter CSI and Calcium Hardness: big number really right?​

The OP in that thread is trying to nail down a year-round number for CH that satisfies his goals for the saturation index.

 

[Texas Splash]

that at the point where CH gets actively decreased in summer, and then increased again in winter, the line towards micromanaging has been well and truly crossed.

This is really the main point. Same thing with @ajw22 's comment in Post #2 from that other thread.

Ignore the CSI in the winter.
Keep your CSI in range about 9 months out of the year and your pool will be fine.

Remember that CSI is simply one tool in your TFP toolbox. For the majority of pools, simply managing all parameters within TFP recommended levels will result in good sanitation and chemistry for the pool shell and equipment. Consider that even those up north buried under several feet of snow know their pool is fine until spring. For those of us in moderate temperatures with pools still running, our biggest concern is scale, especially in warmer water months, at which point then we might focus more on the CSI to ensure it does't get too high.

It's good to be vigilant, but try not to obsess too much about CSI. Don't let it get to you or you'll go nuts.

 

[an1vrsy]

Of course I'm aware there is an AGGRESSIVE:OK:GREAT:OK:SCALING range, with there being a wide "OK" range on either side of GREAT, which means we don't have to be at exactly a 0.0 CSI, but still - I'm finding, essentially, the following:

• Summer = I have to lower the calcium levels to get closer to a 0 CSI
• Winter = I have to raise the calcium levels to get closer to a 0 CSI

Using your scale (no pun intended) above, I keep my CSI within the two OKs. In the winter, I am more on the negative OK side up to great just by managing pH. I don't consider it chasing pH by adding half a gallon of muriatic acid when it gets to 8.0 and that will knock it down to about 7.6 or so. It takes about a week to get back up to pH 8.0. Current water temp is 48 degrees.

My CH is pretty stable at 370 ppm due to my softened make up water. My TA is what it is due to high TA fill water, here of about 140 ppm. In the winter I use less MA so TA rises to its current level of 130. In the summer with the SWG running and lots of swimming and splashing around, and much higher evaporation so lots of fill water, I use a lot more MA and the TA gets down to 90. With what I have learned here on TFP, I pretty much just use MA to manage CSI winter or summer and keep the CSI within acceptable range -0.3 to +0.2, I don't try to keep it at zero. I'd probably pull my hair out doing that.

 

[Gary Davis]

Remember that CSI is simply one tool in your TFP toolbox.

You bring up a good point where I would like to outline the MAIN chemical tools we have in our arsenal, which might be listed as:

1. The number one chemical tool is (of course), free chlorine
   • (which is greatly related to CYA & CC & temperature, but not so much to pH or any other chemical factor for an outdoor pool).
2. The number two chemical tool is the saturation index
   • (which is greatly related to temperature & pH & TA & CH and less so to TDS & Borates for an outdoor pool)

My observation is that these are the two most important tools we have in our chemical arsenal.

1. FC
2. CSI/LSI

Notice what I'm implying here which is that the CSI/LSI is the second most important chemical factor, and there are only two of them that matter.

• The rest are just components of those two (IMHO).

This means that the saturation is second ONLY to sanitation, or, put in other terms, the only two things you care about are:

1. Sanitation
2. Saturation

For the majority of pools, simply managing all parameters within TFP recommended levels will result in good sanitation and chemistry for the pool shell and equipment. Consider that even those up north buried under several feet of snow know their pool is fine until spring. For those of us in moderate temperatures with pools still running, our biggest concern is scale, especially in warmer water months, at which point then we might focus more on the CSI to ensure it does't get too high.

Scale...

I can understand that scale is a big factor for people who use electrolysis to generate the chlorine, but much (much) less of a factor for those of us who do not.
That means, I think, we have three different (overlapping) types of outdoor pool owners in terms of the saturation index.

1. SWCG pools (plaster or non plaster)
2. Plaster bleach pools
3. Non-plaster bleach pools

As far as I can tell, those with SWCG need to care greatly about scale, but the other two types need to care less about scale since it's less of a problem overall.
For example, as far as I can tell, plaster bleach pools don't really have a problem with scale as it does nothing much other than look white (and is easily cleaned).

Those of us without the extreme SWCG sensitivity to scale don't worry at all about scale (other than it looks white on the tiles - which causes no harm); what we worry about is aggressive water since we care about our plaster not being leached out during the cold weather months (which, IMHO, is the very critical time to care MOST about saturation, contrary to what many others seem to think).

In other words, whether or not you care about scale depends a LOT on how you get chlorine into that pool.

• For me, with a plaster bleach pool, scale is not important in the least in terms of damage - what's important is leaching
• And, the most important time of the year for leaching is winter (due to the saturation index plummeting in colder temperatures)

It's good to be vigilant, but try not to obsess too much about CSI. Don't let it get to you or you'll go nuts.

I fully agree that people can go nuts with CSI, but I disagree slightly with those who say to ignore it in the winter (for a bleach plaster pool).

• The winter is, IMHO, precisely the time to CARE MOST about saturation for a bleach plaster pool (as that's when the damage occurs).

Saturation is the second-most important chemical component in managing our pool chemistry, is it not?
And there are only two components overall - so it seems to me that saturation is critically important.

What else is there, chemically speaking, other than these two components?

• You manage your sanitation
• You manage your saturation

Is there anything else that you manage, chemically?

 

[DrewLG]

Are you ever successful in balancing the Calcium Saturation Index without having to adjust the alkalinity and/or calcium saturation by a large amount?

I'm in California, so in the winter I have the same problem as you. If you look at my PoolMath logs you'll see that my TA and CH have been very diluted by the recent rain, so my CSI is now close to -1.

I'll compensate by adding a little CaCl and baking soda this week. Not so much that I'll need to actively lower TA and CH six months from now; just enough to hit the low edge of the PoolMath-recommended CH and TA values: 50 TA and 250 CH.

That will raise my CSI to just above -0.6 if I keep the pH constant at around 7.8, and I'll be happy to allow CSI to stay there until spring/summer, when higher temperatures and my fill-water CH/TA will push CSI up to around 0.

 

[Zalligan]

On the topic, I want to listen to all the folks that say to not worry about CSI in the winter, but for those of us with heaters, shouldn't we be concerned about scaling in the heat exchanger, or is it less susceptible than the sensitive plates of an SWCG? I've been playing the rather frustrating game of chasing CSI myself this winter (new pool owner) with pool "closed" (covered, SWCG removed, pump running, manually dosing w/ chlorine) so I'm obviously not worried about the SWCG, but I'd rather not just ignore the potential for scale to build within my heater for the 4-5 months that I'm "closed" here in NTX.

 

[BowserB]

I'm so far from expert that even calling me a novice seems generous. However I read advice and take it, when it makes sense. CSI at +/- 0.6 is what I read a lot. I also read that scale is bad for a heater and is bad for a SWCG, and that therefore keeping the CSI from 0 to -0.6 is optimum for those sensitive and expensive components. So that's what I shoot for, summer-fall-winter-spring. I also read that algae is bad, and free chlorine prevents it, so I keep my free chlorine between 4 and 6 ppm with erring on the high side being my preference, so 6ppm is not the top of my range but more the target.

 

[mgtfp]

On the topic, I want to listen to all the folks that say to not worry about CSI in the winter, but for those of us with heaters, shouldn't we be concerned about scaling in the heat exchanger, or is it less susceptible than the sensitive plates of an SWCG? I've been playing the rather frustrating game of chasing CSI myself this winter (new pool owner) with pool "closed" (covered, SWCG removed, pump running, manually dosing w/ chlorine) so I'm obviously not worried about the SWCG, but I'd rather not just ignore the potential for scale to build within my heater for the 4-5 months that I'm "closed" here in NTX.

If you are not concerned about scaling in summer, I don't see how that should become a problem in winter.

The discussion here was more about balanced water in summer becoming a bit more CSI negative for a few weeks in winter.

 

[Gary Davis]

I'm in California, so in the winter I have the same problem as you. If you look at my PoolMath logs you'll see that my TA and CH have been very diluted by the recent rain, so my CSI is now close to -1.

Thank you for confirming what I'm seeing, which is kind of paradoxical because my (uncovered) pool (chemistry) is also being diluted GREATLY by the rain.
Here's what's confusing about that.

• Last September & October, I had let the water level drop about a foot and a half (knowing the rains would likely come)
• Then the rains (this year) filled that remaining foot in no time at all (way back in November)
• In December & now January, the rains have been consistently coming like a river of water
• But.... now that the pool has been overflowing for months - why is it STILL diluting the chemistry?

Why, with the pool completely full to the overflow drains, is its chemistry STILL being diluted by the rains?
How does that work?

I'll compensate by adding a little CaCl and baking soda this week. Not so much that I'll need to actively lower TA and CH six months from now; just enough to hit the low edge of the PoolMath-recommended CH and TA values: 50 TA and 250 CH.

Thanks for that strategy, where it's different that you have to raise the TA, as I ALWAYS need to lower it (which is more expensive than raising it would be).

To keep the saturation index in check, I generally strive for a roughly 1:3 or 1:4 ratio of TA to CH where I greatly dilute an ounce or two of MA into a 5-gallon bucket of water and sometimes even that I dilute again into two five gallon buckets - and then widely disperse it into the pool. The reason for that approach is that dilution prevents the MA (which is much heavier than water) from "columizing" to the bottom and then leaching the plaster a bit (which, if it happens, defeats the purpose of the MA in the first place).

• You can't dilute MA too much.

Once I add the MA, I then add the Snow Joe, also greatly diluted, but for different reasons, as the stuff gets hot (as you know) when it dissolves in the five gallon bucket, and it doesn't dissolve all that well so if you put too much, you end up with it on the pool floor (nothing we put in the pool is lighter than water I don't think).

• Every time I add a pound of Snow Joe, I "feel" like I'm saving a pound of plaster from etching!

It seems that your judicious adjustments are keeping your saturation in check, so I will take heart that it can be done, even with these torrential downpours we've been having lately.

Unfortunately, some California winters are bone dry, but some are wet like this one - so it's harder to plan ahead as it's not consistent here.

That will raise my CSI to just above -0.6 if I keep the pH constant at around 7.8,

On the topic of pH, for an outdoor pool (which has CYA to stabilize the chlorine), for sanitation purposes, I don't try to manage the pH at all since the pH is (almost) completely meaningless in terms of sanitation (despite what many people may say otherwise - but who don't understand how CYA changes things a lot).

• However, for saturation purposes, pH matters a LOT!

Hence, I have always been struggling with the basic decision of whether to manage the pH or not, since it doesn't matter for sanitation but it matters greatly for saturation.

• It seems you've decided to manage pH, which is a testament to your will to control the pool chemistry.

I think I have given up trying to 'manage' pH where I let the alkalinity levels determine the pH ceiling & floors.

and I'll be happy to allow CSI to stay there until spring/summer, when higher temperatures and my fill-water CH/TA will push CSI up to around 0.

I like the way your plan works, where you've already accounted for the change in saturation given the inevitable warming of the water come spring and the inevitable addition of fill water during the summer months.

Your sig appears to indicate your pool isn't a SWCG so if that's the case, any winter 'scale' is less of a problem than the damage from 'aggressive' water to your gunite surface.

It's interesting, but I think everyone cares about 'aggressive' saturation about the same, but people care wildly differently about 'scaling' depending on whether how they're adding the chlorine.

• Everyone with gunite/plaster surfaces cares greatly about 'aggressive' saturation levels
• And people with SWCG seem to care greatly about 'scaling' saturation levels
• But those of us using bleach as the chlorine source seem to not have much problems with scale
  • It's just unsightly, but not harmful (all the unnecessarily dire warnings from pool stores notwithstanding)

Thank you very much for your local advice, where the rains have been a 'beach this year, haven't they!
My main confusion, I think, is why are the rains still DILUTING my chemistry when the water level has been consistently at the overflow drains.

 

[DrewLG]

My main confusion, I think, is why are the rains still DILUTING my chemistry when the water level has been consistently at the overflow drains.

I'm not sure I understand. If you pour a cup of coffee and set it in the sink under a dripping faucet, the water in the cup will eventually be clear. Why would a pool be different?

 

[Gary Davis]

I'm not sure I understand. If you pour a cup of coffee and set it in the sink under a dripping faucet, the water in the cup will eventually be clear. Why would a pool be different?

I don't know. I'm the one who is confused.

One way I "can" look at it is that rain water (might be?) lighter than pool water, and it's only the top surface which is spilling.
Maybe the top inch or two.

I don't run the pumps all winter so the only "circulation" is adiabatic or wind driven (which might be appreciable, come to think of it).
I guess if I assume the water is NOT circulating, then only the rain water is "floating" on the surface and spilling into the overflows.

But as I'm typing this up, I realize a flaw in my confusion is that the water is probably mixing more than I'm allowing for.
In which case, it's diluting my carefully planned chemistry even deeper down in the thermocline layers than I may have accounted for.

Drat.

As Moltke? is said to have said in the Franco Prussian war, no carefully choreographed pool chemistry attack plan survives contact with the rain water (or something to that effect).

 

[mgtfp]

If you're not running the pump, then the water is only very slowly mixing, and the top layers are probably way more diluted than the bottom layers. Try taking a sample from further down, for example with a long PVC pipe à la @Dirk:

First tests with proper test kit; and is it time to replace some water?

Just a follow up question but are there any effective filters you can attach to a garden hose to filter calcium out of water as you're adding it to the pool? I've seen a few things as I've searched around but just wondering if these are effective.

www.troublefreepool.com

If you are worried about rain diluting your water, then I don't really understand why you drained water to make room for rain. That's what we recommend when someone wants to reduce for example slightly elevated CYA or CH levels to get the maximum dilution effect: Drain off in advance as much undiluted water as possible, to wash as much of the unwanted substance down the drain as possible, and then give the rain a chance to mix in before it drains off over the overflow.

If you want to minimise dilution, then keep the pool filled to the overflow, and don't run the pump when it's raining. Like that you maximise the volume of rain water to drain off straight away before it has time to mix into the bulk water.

 

[Dirk]

I didn't read this whole thread, just some thoughts on the last couple posts:

Whether you run an SWG or not, all pools are salt water pools (after a while). Chlorine, pool acid, and those pesky humans all leave salt behind after they're done doing their thing in your pool. Salt doesn't evaporate, so it collects in your pool. The only way it leaves is via splash out or drainage (intentional or overflow). So your pool water has some amount of salt in it.

Rain water (the freshest of fresh water) floats on top of salt water. Temperature differences can also create layers of water in your pool.

If your pool has an overflow outlet at the surface, during and right after a rain, it is the fresh water that is draining out of the pool. There will be some mixing of the fresh and salt water layers, of course, but mostly fresh water is leaving your pool.

The only way to test accurately is after about 30 minutes of circulation. If you can't, or won't, run your pump, your test results will be inaccurate. There is no practical way of determining by how much.

If you can't run your pump, you could use a $50 sump pump to stir the pool. It might take longer than 30 minutes. Or I suppose you could sample water at different depths and average the test results. I have no idea how reliable the end result of that effort would be.

If your pool has an auto-leveling system like mine, fill water and overflow enter/leave the pool through an equalizer pipe outlet which is a few feet below the surface. During a rain, the fresh water floating on top is pushing out the salt water from down below the surface. This works great to rid my pool of the calcium and salt it collects throughout the year. Well, when it rains in CA, that is. This year has been great. My excess CH has dropped about 90ppm over the last month or two. Basically a free water exchange. Unfortunately, I did a manual exchange in October, because my CH was high. I should have waited until Spring, after the rains, because I wouldn't have had to exchange as much as I did. Lesson learned. In my defense, who knew CA would ever get rain again!!

If the Spring, I'll add whatever CYA and salt I need, and be all set for swim season!

 

[Newdude]

Forgive the crude drawing, but you'll get the point.



Regardless of where the overflow is located, we can split the pool like my drawing into thirds and any water falling in A or B will raise and overflow C faster than C is being filled. The A and B rainwater have a long way to get out the pipe, while not mixing with any existing water along the way. In a heavy downpour the surface layer(s) get a decent amount of mixing, and the accompanying winds will help stir it a little also.

The overflow water is definitely diluted but some collateral damage is inevitable. Especially with the several inch storms you guys have been getting pounded with.

 

[Gary Davis]

If you're not running the pump, then the water is only very slowly mixing, and the top layers are probably way more diluted than the bottom layers. Try taking a sample from further down, for example with a long PVC pipe.

That's an interesting idea to sample the water deeper down with a pipe using a pvc pipe and putting your finger over the top when withdrawing the water from deeper down. It also saves having to get down on bended knee onto a hard pool deck for old guys like I am.

Thanks! I see Dirk used caps with holes but I'll bet it would work with nothing other than the pipe itself (smaller diameter maybe).
I'll try it out.

If you are worried about rain diluting your water, then I don't really understand why you drained water to make room for rain. That's what we recommend when someone wants to reduce for example slightly elevated CYA or CH levels to get the maximum dilution effect: Drain off in advance as much undiluted water as possible, to wash as much of the unwanted substance down the drain as possible, and then give the rain a chance to mix in before it drains off over the overflow.

I should have been clear that the lowered water level was due to evaporation only. We get a LOT of sun in California. I lose something like an inch a day (or whatever, but it would be a foot in a month so I guess that's half an inch a day or thereabouts). So all I did was NOT refill it after the swim season was over.

If you want to minimise dilution, then keep the pool filled to the overflow, and don't run the pump when it's raining. Like that you maximise the volume of rain water to drain off straight away before it has time to mix into the bulk water.

In effect, with all this rain, and with the fact I'm not running my pumps in the winter, that is what I'm doing in practice.
Thanks for that idea for getting the water deeper down.

If nothing else, my knees will thank you every time I do it!

 

[Newdude]

In effect, with all this rain, and with the fact I'm not running my pumps in the winter, that is what I'm doing in practice.

So the pumps don't come on at all ? Do you mix before you test ?

I asked because my pool numbers bottom out during/after the winter. I need to mix for a full day before I trust them because they're iffy at best with a couple hours of the pump running.

@PoolStored is another one who sees this and it could very well account for a chunk of your loss and given more time it will stratify further.

 

[mgtfp]

In effect, with all this rain, and with the fact I'm not running my pumps in the winter, that is what I'm doing in practice.
Thanks for that idea for getting the water deeper down.

If nothing else, my knees will thank you every time I do it!

I guess with the pump not running, there will always be a bit of a gradient between "old" pool water at the bottom and fresh rain water at the top. But since the bulk of the water is "old" water, taking a sample from further down should still be closer to the actual water composition after mixing than taking a sample close to the surface.

 

[Dirk]

Thanks! I see Dirk used caps with holes but I'll bet it would work with nothing other than the pipe itself (smaller diameter maybe).

You'll find it won't. You might be able to work the top well enough, blocking it with your thumb, but it won't be convenient, especially when bending over to get it down into the water. The bigger problems are: the water will tend to fall out of the bottom as you bring it out of the water, and if your sample container has a narrow neck then you'll lose another chunk of water aiming the bottom of the pipe at the container (picture: the container in your left hand, your right hand 30" away, at the top of the pipe holding your thumb over the top, while trying to aim the 30" of pipe at the little opening in the container).

Yes, a smaller pipe would work, but 30" of 3/4" PVC is about the amount of water needed for a full suite of tests. It fills a Leslie's water sample container perfectly (which is sized for the correct amount of water). With a smaller pipe, you'll need to dip at least twice.

I've already worked all this out. The pic I posted is actually the prototype. I redesigned/replaced it with the "current model," based on trial and error. But be my guest if you want to do it again! Maybe you'll think of something I didn't.

Otherwise:
- 30" @ 3/4" PVC
- top 3/4" cap with 1/2" hole drilled through it
- bottom 3/4" cap with 5/16" hole drilled through it

You can flip the pipe over to get two different flow rates, if you find one is too slow or too fast.

You don't need to glue the caps.

I thought I noticed recently that the Leslie's samplers are now smaller than the ones I have. I'm glad I nabbed two of them. They hold just over 1 cup. I usually run very close to emptying that when I do a full suite of tests, as I use the same water to rinse everything before each test.

You can carry the sample in just about anything, of course, but the Leslie's cap is the key. It allows perfect metering of the sample water into the test vial, down to a drop.