Recommended levels

[JasonLion]

Traditional sources usually provide a single set of recommended levels for all pools. Generally these levels are balanced for plaster pools using trichlor and are less appropriate in other situations. Traditional sources also leave a great deal of confusion about when it is very bad to get out of range vs when it is not that big a deal to get out of range.

It would be nice to have a set of different recommendations for different situations with more information about when the limits are important and when they are "soft". Unfortunately, listing all the special cases tends to cause confusion. There are tricky questions about the balance between giving accurate information and exceeding people's capacity to understand what you are saying. This is particularly troublesome when talking about calcium saturation, which most people have trouble following.

I started listing out all the various special cases for the various levels and I quickly came up with two pages of fairly dense technical information. I can't see any simple way to explain things that comes anywhere close to as simple as the list of upper and lower bounds for each level offered by the traditional sources. For example, on CH even a simple list comes out to something like:

Vinyl, no aeration: 50 to 300, ideal 150
Vinyl, significant aeration: 100 to 300, ideal 150
Fiberglass 100 to 400, ideal 250
Plaster: 200 to 400, ideal depends on CSI balance
High CH fill water: 200 to 1,200, requires careful management of CSI
Overall Limits: 0 to 1,200, depending on CSI balance

It is already too long, and saying "depends on CSI balance" leaves a great deal unsaid.

 

[chem geek]

The only change I would make is not to have a low end of zero for any case. Perhaps 50 or 100, but not zero. I think the jury is out on what happens with corrosion with zero calcium -- yes in theory only dissolving of calcium carbonate should be an issue and not metal corrosion, but I'm not sure it's a risk worth taking. As you indicated with aeration one can get foaming and a CH level of 100 or so helps prevent that.

Perhaps I'm being conservative here, but unlike the pool water chemistry of chlorine/CYA, I don't think the chemistry of corrosion is as well understood or as straightforward. Taking a look at Corrosion Doctors hasn't made me feel confident to ever say that zero calcium is OK.

Richard

 

[Guest]

Vinyl, no aeration: 50 to 300, ideal 150
vinyl above 120. If CH is very high then watch pH to prevent scaling since pH is the main predictor of scaling
Vinyl, significant aeration: 100 to 300, ideal 150
don't worry about the aeraton with vinyl and CH...just use a rule of thumb that the more the aeration the lower the TA
Fiberglass 100 to 400, ideal 250
Fiberglass above 200 to help prevent staining and cobalt spotting. 250 ideal so we are basically talking about the same range for this and plaster except that plaster is ideal at about 300 ppm (assuming low TA and unstabilzied chlorine --BBB)
Plaster: 200 to 400, ideal depends on CSI balance
High CH fill water: 200 to 1,200, requires careful management of CSI
No, high CH fill water requires careful management of pH, NOT CSI!!!!!!

Overall Limits: 0 to 1,200, depending on CSI balance

It is already too long, and saying "depends on CSI balance" leaves a great deal unsaid.

You are making it much too complicated. Instead of talking about CSI just say to monitor pH closely when calcium is high and give ranges for the different pool surfaces. I guarantee that it will be in the ballpark
vinyl 120-300
fiberglass 220-300
plaster 250-350
use the above for 'sweet spot' ranges. If calcium is lower then add. If it's higher keep watch on pH to prevent scaling. It's not rocket science, don't make it that complicated.

Keep pH under 7.8 and TA at 70-90 (uncorrected for CYA) for unstabilized chlorines and 100-120 for stabilized chlorines.

These recommendations are easy to follow and will put the pool right about where it needs to be. Caution not to run pH too low in a plaster pool and you won't have a problem with agressive water...this is why I say pH 7.5-7.8 as the range.

Just my 2 cents.

 

[duraleigh]

Interesting thread. I don't pretend to understand the underlying chemistry but certainly grasp the different ideal levels for different pool surfaces.

There are tricky questions about the balance between giving accurate information and exceeding people's capacity to understand what you are saying.

Well said, Jason. We frequent posters have to remember that the average newbie logging on for the first time does not yet understand why his chlorine has disappeared.

I would like to see an agreed to generalization (like the original 200-400)that would include all pool surfaces and keep them in a reasonably safe range....say 180-300 perhaps.

The real epiphany for the newbs is when they understand the CYA/chlorine relationship and that's about the only complex information I think they should be subjected to initially.

Now, Evan, before you post back that "this stuff is easy"....No, it's not. What people do everyday is "easy" because they have learned it. Your profession (and pool water chemistry) may seem easy to you but it's not too others. What I do to earn money is "easy" for me because I've done it for 30 years...others find it intimidating.

Perhaps we can work towards an intermediate portion of the forum where folks that have gotten their pools cleared up can go to fine tune and adjust their levels for different situations. Multiple Alk levels, multiple CH levels, borates, etc. are all things that, IMO, are just a little too much info for the guy who hasn't chlorinated in a month and can't understand why his pool has "a greenish tint" !!

 

[Guest]

Interesting thread. I don't pretend to understand the underlying chemistry but certainly grasp the different ideal levels for different pool surfaces.

There are tricky questions about the balance between giving accurate information and exceeding people's capacity to understand what you are saying.

Well said, Jason. We frequent posters have to remember that the average newbie logging on for the first time does not yet understand why his chlorine has disappeared.

I would like to see an agreed to generalization (like the original 200-400)that would include all pool surfaces and keep them in a reasonably safe range....say 180-300 perhaps.

The real epiphany for the newbs is when they understand the CYA/chlorine relationship and that's about the only complex information I think they should be subjected to initially.

Now, Evan, before you post back that "this stuff is easy"....No, it's not. What people do everyday is "easy" because they have learned it. Your profession (and pool water chemistry) may seem easy to you but it's not too others. What I do to earn money is "easy" for me because I've done it for 30 years...others find it intimidating.

Perhaps we can work towards an intermediate portion of the forum where folks that have gotten their pools cleared up can go to fine tune and adjust their levels for different situations. Multiple Alk levels, multiple CH levels, borates, etc. are all things that, IMO, are just a little too much info for the guy who hasn't chlorinated in a month and can't understand why his pool has "a greenish tint" !!

You are all making this much harder than it needs to be. Don't talk about CSI or chlorine/cya relationships at all. Just start with the type of pool and give separate levels for the calcium, the other numbers will be the same for all three pool types. chlorine 3-5, cya 30-50 and it's a done deal! pH 7.5-7.8 done deal. TA 70-90 (uncorrected for CYA IF anyone asks) for bleach and it's cousins and 100-120 for trichlor. If CC is above .5 ppm shock.
This is all a beginner really needs to know to keep a pool near perfect.

Sorry Dave, it IS easy!

If it's a new fill balance TA, then pH , the CH THEN add chlorine and cya. IF any of the balancing is going to be involved handle it as a special case ...just have them keep some chlorine in the water until everything is balanced.

 

[chem geek]

I think a rule of having the FC target be 10% of the CYA level is pretty darn easy. That way, if a pool has a lot of direct sun and someone wants to reduce chlorine usage with 60-80 ppm, they know they need to use 6-8 ppm FC. Having separate FC and CYA ranges only works if those ranges are very narrow so while OK with the 30-50 CYA 3-5 FC you quote, it won't work as the CYA rises above 50 as it will usually do if one uses Trichlor.

Realistically, until coming here very few check their CYA level even though there is the recommended range from pool stores (usually 30-100). Understanding that higher CYA requires higher FC is key to getting people to know why it's so important to measure the CYA level and to understand that stabilized chlorine will increase it much faster than they might think.

 

[JasonLion]

Chem Geek - I like the idea of playing it safe and recommending at least some low CH level. But I also note that many public water supplies have low CH and don't experience corrosion. Adding CH can be a significant expense. It is difficult to know where to draw that line without any data to back things up.

Waterbear - I can certainly see how getting rid of CSI makes things much simpler for novices, which is my goal here. I feel that CSI does have a place, particularly for people trying to manage CH levels around 1,000, but not for novices. It seems likely that the CH levels around 1,000 discussion requires a Pool School article or sticky of it's own and should only be referred to in the recommended levels section without any discussion.

Why do you say that CH should be 120 for vinyl pools? Ben was always adamant that no CH was required with vinyl and there are a couple of testimonials over at PF from people with CH around 10 saying it worked just fine for them.

Duraleigh - I very much doubt that we can reduce things to a single set of numbers for all pools. There are two distinct CYA levels we routinely recommend. There are at least two TA ranges, using trichlor and not, that are important, and high aeration argues for a third range (though that is less clear). I think the best we can hope for is two or three possible ranges for each chemical depending on one thing or another.

 

[Guest]

I think a rule of having the FC target be 10% of the CYA level is pretty darn easy. That way, if a pool has a lot of direct sun and someone wants to reduce chlorine usage with 60-80 ppm, they know they need to use 6-8 ppm FC. Having separate FC and CYA ranges only works if those ranges are very narrow so while OK with the 30-50 CYA 3-5 FC you quote, it won't work as the CYA rises above 50 as it will usually do if one uses Trichlor.

Realistically, until coming here very few check their CYA level even though there is the recommended range from pool stores (usually 30-100). Understanding that higher CYA requires higher FC is key to getting people to know why it's so important to measure the CYA level and to understand that stabilized chlorine will increase it much faster than they might think.

Once again you are getting into advanced topics and not recommended levels as the title of this thread shows. Recommended level of CYa is 30to50 and /Fc lf 3-5 works pretty darn good in that CYA range.

Keep is simple, keep the advanced stuff for later. I deal with pool newbies all the time and I have the advantage to be able to see when their eyes start to glaze over. What I am saying just about anyone (with a few exceptions I won't mention because they might read this!) can grasp what I posted above. The hardest part they will have is learning how to test and figuring out the pool calculator. Actually, for a newbie I think bleachcalc is easier and less confusing since it's only presenting one calculation at a time (sorry Jason). Just wish it didn't have that borate error but then again, by the time they are ready to add borates they are probably ready for the calculator.

One a pool has been gotten into range THEN you can start dealing with special cases like running higher CYA for pools that get a lot of sun. Pools that can't be brought into these recommended levels should be dealt with on an individual basis. (such as fill water high in calcium) since they are the exception and not the norm.

 

[JasonLion]

Here is my complete set of much simplified yet still too complicated recommendations.

FC
Depends on CYA level
Limits: minimum to high/mustard shock level
Plaster can go higher for a few days

PH
PH is stable: 7.4 to 7.6, ideal 7.5
PH drifts: 7.2 to 7.8, ideal 7.5
High aeration: 7.6 to 7.8
Limits: 7.0 to 8.0
Plaster can go to 6.8 for a few days

TA
SWG or high aeration: 60 to 80
Bleach: 70 to 90
Trichlor: 100 to 120
Limits 50 to 250, depends on CSI balance and PH drift

CH
Vinyl, no aeration: 50 to 300, ideal 150
Vinyl, aeration: 100 to 300, ideal 150
Fiberglass 100 to 400, ideal 250
Plaster: 200 to 400, ideal depends on CSI balance
High CH fill water: 200 to 1,200, requires careful management of CSI
Limits: 0 to 1,200, depends on CSI

CYA
Indoor: 0 to 20, ideal 20
SWG or high sunlight: 60 to 80
Otherwise: 30 to 50
Limits indoors: 0 to 30
Limits outdoors: 20 to 90

Borates
None: 0
Feel/algaecide/PH buffer: 30 to 50
Limits: 0 to 80

Salt
None: 0 to 1,000
Feel: 1,000 to 2,500, ideal varies by individual
SWG: depends on brand/model, typically around 2,500 to 3,500
Limits: 0 to 5,000

 

[Guest]

Why do you say that CH should be 120 for vinyl pools? Ben was always adamant that no CH was required with vinyl and there are a couple of testimonials over at PF from people with CH around 10 saying it worked just fine for them.

Very simply, hard water has less tendency to foam than soft water. I started having some customers that were filling with softened water because they had iron and they were complaining that their pools would foam a bit. Their calcium hardness was basically non existant. I found that once the calcium got a bit above 100 ppm the foaming basically stopped which is why I say 120 ppm.
My recommendations for fiberglass come from all the research I've done on staining and cobalt spotting in fiberglass pools (I've had both!) and now that my CH is between 250-300 both problems have vanished. I let the hardness drop (I fill with softened water because there is NO bypass on my water softener!) and my stains returned! when it hit around 180-190 ppm.

 

[Guest]

Here is my complete set of much simplified yet still too complicated recommendations.

FC
Depends on CYA level
Limits: minimum to high/mustard shock level
Plaster can go higher for a few days

PH
PH is stable: 7.4 to 7.6, ideal 7.5
PH drifts: 7.2 to 7.8, ideal 7.5
High aeration: 7.6 to 7.8
Limits: 7.0 to 8.0
Plaster can go to 6.8 for a few days

TA
SWG or high aeration: 60 to 80
Bleach: 70 to 90
Trichlor: 100 to 120
Limits 50 to 250, depends on CSI balance and PH drift

CH
Vinyl, no aeration: 50 to 300, ideal 150
Vinyl, aeration: 100 to 300, ideal 150
Fiberglass 100 to 400, ideal 250
Plaster: 200 to 400, ideal depends on CSI balance
High CH fill water: 200 to 1,200, requires careful management of CSI
Limits: 0 to 1,200, depends on CSI

CYA
Indoor: 0 to 20, ideal 20
SWG or high sunlight: 60 to 80
Otherwise: 30 to 50
Limits indoors: 0 to 30
Limits outdoors: 20 to 90

Borates
None: 0
Feel/algaecide/PH buffer: 30 to 50
Limits: 0 to 80

Salt
None: 0 to 1,000
Feel: 1,000 to 2,500, ideal varies by individual
SWG: depends on brand/model, typically around 2,500 to 3,500
Limits: 0 to 5,000

TOO MUCH INFORMATION!!!!!!!!!!!!! Make it simpler! SWGs are a special case. Indoor pools are a special case. HIgh CH fill water is a special case! KEEP IT SIMPLE and handle special cases on a case by case basis or with common special cases like SWGs refer them to a different set of guideliens like the one I wrote! If you have 30-50 ppm CYA for manually chlorinated and 60-80 (70-80 is better) for SWGs then FC is 3-5 in either case. Keeps it simple! pH 7.5 to 7.8...when it goes above 7.8 add acid to lower to 7.5-7.6....not hard to do. Get the picture?

 

[Guest]

How about this:
Plaster pool
FC 3-5
pH 7.5-7.8
TA 70-90 unstabilized CL and SWG
100-120 stabilized CL
CH 250-350 (I give a smaller range because the ends of the range 200-400 can quickly become special cases, particularly if there is a testing error, which is common with newbies.)
CYA 30-50 (70-80 for SWG)

Fiberglass
FC 3-5
pH 7.5-7.8
TA 70-90 unstabilized CL and SWG
100-120 stabilized CL
CH 220-320 (This is actually in line with most of the major fiberglass manufacturers who recommend ranges from 175-225 to the standard 200-400)
CYA 30-50 (70-80 for SWG)

Vinyl
FC 3-5
pH 7.5-7.8
TA 70-90 unstabilized CL and SWG
100-120 stabilized CL
CH 120-350
CYA 30-50 (70-80 for SWG)

Anything outside of these ranges should be treated as a special case. Indoor pools treat as a special case. People with very high calcium treat as a special case (easy one, just watch the pH and possibly lower TA even more!). Someone with CYA over about 60-70 ppm who does not want to drain is a special case AND a head case. Not worth trying to do a high chlorine pool until you have the basics down. It's an invitation to a green disaster! It's really NOT hard, just treat the special cases as special cases. The vase majority of pools will fall within these guidelines. If they are not the water is not in balance and needs to be balanced, plain and simple.

Salt depends on the brand of SWG. If adding salt for the feel it is NOT a beginner topic.
Once the pool is balanced and stable THEN you can go on to intermediate topics of salt for non SWGs and adding borates (however I strongly believe that once a SWG pool is stable borates SHOULD be added!)

 

[JasonLion]

I prefer a slightly different presentation, something more like:

-----

FC: 3-5 and never below 3
PH: 7.5-7.8
TA: 70-90, except with dichlor & trichlor: 100-120
CH: vinyl & paint: 120-350, plaster & pebble: 250-350, fiberglass: 220-320
CYA: 30-50, except with SWG use 70-80

For high CH fill water see <Dealing with High Calcium>.
For large amounts of aeration (negative edge, always running waterfall, etc) see <Dealing with High Aeration>.
For extreme amounts of sunlight see <Dealing with Lots of Sunlight>.
It is possible to compensate for various numbers being out or range, if getting one of your numbers into range will be particularly difficult ask for advice on the forum.

-----

One of the big risks with a recommendation like this one is that people get obsessed with hitting the numbers exactly. That is why I was giving "limit" ranges. With better formatting there is probably a way to show that so it doesn't distract too much.

There are several numbers here that bother me.

I would give FC a wider range. Slightly high FC doesn't hurt much but set FC to 5 with CYA at 30 in the morning and it will be below 3 in the evening. So I would go 3-6 or even 3-7.

PH 7.5-7.8 feels like too much of a compromise to the special case of aeration. This is not a good range for plaster startup and it is not ideal for trichlor either. I am not even sure I agree for aeration, though that is a much more difficult call. In general, quite a few people have trouble keeping PH within 7.2 to 7.8, narrowing the width of the range for .6 to .3 is going to make things difficult for many people.

The narrower you make the CH range the more difficult it is to maintain if your fill water has any real amount of CH in it.

Why CYA 70-80, instead of the more common 60-80?

 

[duraleigh]

Given the CH ranges that Jason and Evan proposed just above, what's the harm in 250-350 for all pools?

It catches plaster, fibreglass, and is only a little high for vinyl......or we could exclude vinyl as not necessary (although the anti-foaming property is a potentially nice feature.)

Jason, you indicated CH is pricey. I didn't know that.....I assumed it was cheap like salt. I have never needed it.

I'll always champion the least data possible to get the pool "un-green" and then let the newbies branch out from there.

Twice or more, I remember the word "exceptions" used above. Perhaps we could have an "Exceptions to the Norm" area where those special circumstances could be discussed and advice offered.

You know, this is simply about presenting the collective knowledge of this forum in a simple, cohesive, logical manor. That we're already having to discuss the subject is indicative of the growth here (and what's coming) in one short year.

 

[JasonLion]

CH increaser isn't ridiculously expensive or anything, but you do notice it. Raising CH by 100 in 20,000 gallons costs around $45 from most pool stores. DowFlake would be half that much, but I haven't been able to find any around here yet. For a novice with a vinyl pool who can't find DowFlake that could easily mean $100+ for CH. Chances are they don't need it and won't notice any difference once they add it.

For comparison, increasing salt by 1,000 in 20,000 gallons is around $20 using salt from Home Depot or Lowes. That means $40 to $60 total for salt, depending on starting level, and a much more obvious difference.

 

[Guest]

CH increaser isn't ridiculously expensive or anything, but you do notice it. Raising CH by 100 in 20,000 gallons costs around $50 from a pool store. DowFlake would be half that much, but I haven't been able to find any around here yet. For a novice with a vinyl pool who can't find DowFlake that could easily mean $100+ for CH. Chances are they don't need it and won't notice any difference once they add it.

For comparison, increasing salt by 1,000 in 20,000 gallons is around $20 using salt from Home Depot or Lowes. That means $40 to $60 total for salt, depending on starting level, and a much more obvious difference.

Most pool stores sell calcium in 50 lb bags for around $30-40 dollars (we sell it for $32 and we are now selling Tetra calcium out of texas. Don't know about their bromine content since it's not listed but they do list their calcium as suitable for pool and spa use on their website.(Jason understands what I'm talking about...it's another Deep end topic) Calcium is NOT a major expense and it's not something that has to be adjusted often. It is part of proper water balance however. Why is there a problem with having different recommendations for different pool surfaces? A particular member is only going to have one kind of pool and can disregard the other two, right? First step is what kind of pool do you have and the go to the appropriate area for your pool surface type.
That way vinyl pool users don't waste a lot of money on calcium they don't need but still have enough.

As far as salt goes, you need to be careful with that in AGPs, many of them use steel walls and screws and they WILL corrode and rust when you add salt. That is why I say salt is an itermediate additive and I would use it AFTER borates since borates have many more benefits in stabillizing pool chemistry and in helping prevent algae if the chlorination is not kept up like it should be without have to remember to add polyquat every 2 weeks.

PH 7.5-7.8 feels like too much of a compromise to the special case of aeration. This is not a good range for plaster startup and it is not ideal for trichlor either. I am not even sure I agree for aeration, though that is a much more difficult call. In general, quite a few people have trouble keeping PH within 7.2 to 7.8, narrowing the width of the range for .6 to .3 is going to make things difficult for many people.

The narrower you make the CH range the more difficult it is to maintain if your fill water has any real amount of CH in it.

Why CYA 70-80, instead of the more common 60-80?

As far as keeping the pH in the range I suggested it's actually pretty easy. Assuming TA is in the suggested range of 70-90 then 1 pt of acid per 10000 gallons added when the ph hits 7.8-7.9 will lower it to about 7.5 and if the TA is in the higher range for trichor then it will lower it to about 7.6 which is a good place to run pH with trichlor. NOT rocket science and doesn't even require the calculator. A bit of trial and error and testing and soon the person knows exactly what THEIR pool needs. If you want to make it easier then perhaps Dave could start offering or including the acid demand reagent and treatment table in the testkit. (they do have acid and base demand reagents to be used with the small comparator and the R-0014 reagent). This would eliminate a lot of the gueswork if the test is done properly.

calcium that is too high is a special case, what's so hard about that. it's not THAT common a problem

The reason for cya 70-80 is that there is a difference in output percentage needed when the cya jumps from 60 to 70 but not much of a change above 70....70-80 is pretty easy to shoot for.
If calcium is low have them add it, if it's too high it's a special case and they need to keep close tabs on pH. They DON'T need to worry about saturation index numbers, JUST pH!

As far as the limits, I found that confusing and I understand what you are trying to say. I say forget them, Just give a range to shoot for. there is going to be testing error so the ranges are on the conservative side. the closer people get to them the easier their pool will be to maintain. If they overshoot or undershoot they are still 'in range' so to speak.

When you are dealing with newbies you need to tell them do this do this do this, ph should be here and when it climbs to here add acid or TA should be here when it drops to here add baking soda. You need to hold their hand just about every step of the way. We can refer and refer to pool school but we are still going to have to do hand holding and look at each pool individually since these levels are, after all, guildlines, and when you come right down to it EVERY pool is going to be a 'special case' in one way or another.

 

[JasonLion]

Most pool stores sell calcium in 50 lb bags for around $30-40 dollars (we sell it for $32 and we are now selling Tetra calcium out of texas.

Around here, Leslie's sells 45 lbs for $79 (well above their Internet price). The smaller containers, which a normal person could actually lift, cost noticeably more per pound. Three other local stores all cost more than that. The local Lowes and Home Depot have a better price, but it is only in stock for perhaps two or three weeks a year and then they sell out and don't restock till next year. Most Internet prices are around $60+ for 45 lbs by the time you add shipping.

The price isn't a huge deal, but it isn't free either. Why add/pay for something you don't need. If they have foaming they should add calcium. Most people don't have foaming unless they have a spa. From what I have seen foaming is the special case.

On PH, it isn't the adjusting I am worried about. The average novice is lucky to read the PH test to the nearest marked number on the color comparator, something like +-0.2 on a good day. With appropriate instructions they have a reasonable chance of keeping the PH between 7.2 and 7.8. Trying to get it tighter than that takes a noticeable amount of practice at reading the color comparator.

Related issues come up with rapid PH drift, even if you are good at reading the comparator. If you only make small adjustments you need to make them much more frequently. At some point you can't keep up anymore and the PH gets out of bounds because you didn't adjust frequently enough. Larger PH adjustments give you more time between adjustments, which can make the difference between keeping up and going out of bounds.

On salt, we can just say "if you have a SWG follow the instructions that came with it for an appropriate salt level for your unit". Salt for feel is clearly a special case and SWGs vary so refer them to the manual.

No need to mention borates at all.

I completely get what you say about the "limits" idea being confusing. I just wish there was some way of indicating that some of the levels have more leeway than others. I keep thinking of some kind of red/yellow/green approach. Green would go with the numbers we are talking about, yellow would be like my limits idea, red would be "work on fixing this right now". But I haven't though of a way to draw it to get the idea across simply enough. I'll drop it until/unless I think of some new way to present it.

 

[randytsuch]

My 2 cents.

I agree with Waterbear.

I have a fiberglass pool, so I just find the fiberglass section in his post, and see what my recommended numbers are.
I think it is simplier that way, you find the right section, and read the numbers.

Randy

 

[JasonLion]

I think it is simplier that way, you find the right section, and read the numbers.

I can see how that simplifies things. The question is how much of that do we do and is it still simpler by the time we are done.

Pool surface and chlorine source both change the numbers for large numbers of people. Do we split out chlorine source into three categories: dichlor/trichlor, SWG, and bleach/cal-hypo/lithium-hypo, making a total of nine tables (three pool surfaces with each of three chlorine sources)? I suppose that having nine tables isn't the end of the world but it does start to strain the simplicity. I hesitate to break things out by pool surface and not by chlorine source.

Amount of aeration, amount of sunlight, CH/TA level of fill water, and indoor/outdoor affect the numbers for lower numbers of people. I have no problem leaving these factors out of the table. Presumably they would be mentioned below the table with either brief commentary or links to more information.

 

[duraleigh]

It seems that tables might be good visuals to present this info.

Perhaps three tables stacked (but seperate) on the same page that show the parameters of each pool surface. The differences would be spelled out within the tables but, because the tables would be formatted alike, differences from surface to surface would be readily apparent.

That would seem to satisfy the need for simplicity as well as the need to demonstrate the changing info as the surface changes