Tips to make the Liquidator liveable.....

[Water_man]

Chem geek,

It seems to me that the factors in the pool water (pH, TA, CH) have little affect on the problem that we're experiencing inside LQ.
With FC that is probably 80ppm+ on a constant basis wouldn't that raise the pH to a point where the inside of the LQ could never stay inside the safe levels of the csi....causing virtually ANY level of CH to precipitate?

Based on what was reported here so far, I've come to the conclusion that what you suggest may not be true. Although two examples don't make a convincing statistical model, we have two users, one on this thread and one on the other who report low TA and low CH and NO WS.
In this thread pjpool reports TA 80, CH 80 and no WS.
In another thread in this post joenj reports TA 90 and CH 70 and no WS.
IMHO the low CH with the low TA and no WS is not a coincidence. It may indicate a trend.
If we want an ironclad (or shall we call it calciumclad ) convincing proof we should run a poll , as suggested in the other thread.
BTW, the FC at the upper level can run higher than 200 ppm.

 

[cruzmisl]

I have a water feature so I am always adding a little acid to keep the pH down. If it gets really bad it will eventualy cause the floats to lose seal and you won't be able to prime on startup.
Joe

Please give some more details about adding the acid. How dilute is it? How do you add it without stirring the water at the top?
Does the addition actually dissolve existing deposits?
Thanks.

I think he means he adds the acid to the pool, not the LQ.

Correct!

 

[chem geek]

Chem geek,

It seems to me that the factors in the pool water (pH, TA, CH) have little affect on the problem that we're experiencing inside LQ.

With FC that is probably 80ppm+ on a constant basis wouldn't that raise the pH to a point where the inside of the LQ could never stay inside the safe levels of the csi....causing virtually ANY level of CH to precipitate?

Well, from what I've read in these threads, a low CH avoids the problem and a low pH avoids the problem and both of those are a lower saturation index. The only thing that hasn't been tried is a low TA, but I talk more about that below.

As for the high chlorine level and therefore high pH in the water above the bleach or chlorinating liquid layer, the following gives the pH (starting from 7.5 and a TA of 100) and incremental saturation index at various added amounts of added FC:

80 ppm FC --> pH 8.83 --> SI +1.27
40 ppm FC --> pH 8.67 --> SI +1.13
20 ppm FC --> pH 8.41 --> SI +0.90

Interestingly, if I use a lower TA level such as 50 ppm, then the pH goes up higher but the delta increase in SI is higher. Unfortunately, this means that we end up with about the same SI. So my idea of lowering the TA isn't the way to go. Lowering the pH or the CH will work and that's what has been seen so far. You CAN use a lower TA if you add Borates to the pool and in fact you get a large benefit having Borates in the pool even without lowering the TA. If I repeat the above but have 50 ppm Borates in the pool I get the following:

80 ppm FC --> pH 8.19 --> SI +0.69
40 ppm FC --> pH 8.06 --> SI +0.57
20 ppm FC --> pH 7.89 --> SI +0.39

So you can see that having the extra pH buffer of 50 ppm Borates helps a LOT to prevent the pH from rising as much due to the bleach or chlorinating liquid. This might be the way to eliminate this problem without having to lower the pH or CH too much and with Borates lowering the TA has the desired effect of a lower final SI (for technical reasons I don't yet know, but that's what the spreadsheet tells me).

This post describes not having the problem and having 50 ppm Borates, a TA of 60 and an SI of -0.13. Then there's this post with low CH and low pH and yet still having white stuff while this post has low CH and no white stuff. So things are not perfectly consistent, but it does seem that if this stuff is calcium carbonate since it dissolves in acid (as opposed to salt that should dissolve in water alone) then the saturation index and the above analysis can help. Of course, if the SI is positive, then other factors come into play in terms of determining the rate of deposition including the amount of nucleation sites such as roughness of tubing and undissolved floating matter in the water, etc.

Richard

 

[mrafal]

Chem geek,

So you can see that having the extra pH buffer of 50 ppm Borates helps a LOT to prevent the pH from rising as much due to the bleach or chlorinating liquid. This might be the way to eliminate this problem without having to lower the pH or CH too much and with Borates lowering the TA has the desired effect of a lower final SI (for technical reasons I don't yet know, but that's what the spreadsheet tells me).

Richard

Richard,

This may help explain why I have not seen the problem, even though I have a CH above 400 and a TA around 60. I do have about 50ppm Borates. I've been running for four months without any signs of accumulation on the float valves.

Marc

 

[Water_man]

If I repeat the above but have 50 ppm Borates in the pool I get the following:

80 ppm FC --> pH 8.19 --> SI +0.69
40 ppm FC --> pH 8.06 --> SI +0.57
20 ppm FC --> pH 7.89 --> SI +0.39

So you can see that having the extra pH buffer of 50 ppm Borates helps a LOT to prevent the pH from rising as much due to the bleach or chlorinating liquid. This might be the way to eliminate this problem without having to lower the pH or CH too much and with Borates lowering the TA has the desired effect of a lower final SI (for technical reasons I don't yet know, but that's what the spreadsheet tells me).



Richard

I measured FC in the upper level as high as 231 ppm when the amount of bleach at the bottom was substantial, and 98 ppm with a low bleach amount, so 80 FC is kind of too low to represent "real life" situation at the LQ.

What does your spreadsheet show for SI for 100 and 200 ppm FC and 50 ppm borates?

Also, apparently this is a supersaturated solution of calcium carbonate and the seeding of crystallization occurs at the interface between a solid and a flowing solution, but the nature of the solid is irrelevant. Thus, for instance, only those parts of the float valve near the flow area are effected.
(I can post a pic if this would help.)
Since the action occurs at the interface, I wonder if adding a small amount of surfactant will do us any good. What comes to mind is stuff like the "Tropical fish solar blanket".

 

[chem geek]

Without Borates,

100 ppm FC --> pH 8.88 --> SI +1.30
200 ppm FC --> pH 9.01 --> SI +1.39

With 50 ppm Borates,

100 ppm FC --> pH 8.23 --> SI +0.73
200 ppm FC --> pH 8.34 --> SI +0.83

So the Borates still clearly help a lot. Remember that somewhere in the range of +0.7 to +1.0 is when scaling is typically seen to start occurring. Having 50 ppm Borates and also having the pH, TA or CH be somewhat lower for perhaps a -0.2 or -0.3 saturation index in the bulk pool water would probably eliminate the problem, but obviously this is something that can only be verified by people trying it out. Perhaps the Borates will be enough in most cases.

There are scale inhibitors and they might be effective, but I hate adding more stuff into the pool. Borates are one thing, but many scale inhibitors are phosphate-based (polyphosphates) and that's not something you want to add to your pool, at least not in large quantities.

Richard

 

[joenj]

Chem geek,

So you can see that having the extra pH buffer of 50 ppm Borates helps a LOT to prevent the pH from rising as much due to the bleach or chlorinating liquid. This might be the way to eliminate this problem without having to lower the pH or CH too much and with Borates lowering the TA has the desired effect of a lower final SI (for technical reasons I don't yet know, but that's what the spreadsheet tells me).

Richard

Richard,

This may help explain why I have not seen the problem, even though I have a CH above 400 and a TA around 60. I do have about 50ppm Borates. I've been running for four months without any signs of accumulation on the float valves.

Marc

What is the source of the calcium deposits in the LQ? Does it come from the bleach or just your CH from your pool? I do not have any deposit problems.

My current numbers for our vinyl pool:
CH 70
TA 90
CYA 50
PH 7.6
FC 3

I am also running with 50ppm borates,,,,,,,interesting!

 

[Water_man]

Without Borates,

100 ppm FC --> pH 8.88 --> SI +1.30
200 ppm FC --> pH 9.01 --> SI +1.39

With 50 ppm Borates,

100 ppm FC --> pH 8.23 --> SI +0.73
200 ppm FC --> pH 8.34 --> SI +0.83

Richard

From the previous post I understand that you used TA =100 for the SI calculation.
What value did you use for CH? Suppose you reduce it by two increments of 50, what do you get for SI?

 

[chem geek]

What is the source of the calcium deposits in the LQ? Does it come from the bleach or just your CH from your pool? I do not have any deposit problems.

The deposits are likely to be calcium carbonate which precipitates (produces scale) when the water becomes sufficiently over-saturated. So in plaster pools where the water is already intentionally saturated with calcium carbonate to prevent pitting of plaster, the high FC content (hypochlorite ion) from the bleach or chlorinating liquid raises the pH of the water and that causes the scale to form.

In your case, your CH is low and you have Borates. Both reduce the likelihood of scaling.

A similar problem happens in an SWG cell at the plate that produces hydrogen gas since it raises the pH, but most SWG cells reverse polarity every so often which dissolves (or breaks off) scale that has formed. The Liquidator does not have that capability such as an auto-blast of acidity to remove the scale.

Richard

 

[chem geek]

From the previous post I understand that you used TA =100 for the SI calculation.
What value did you use for CH? Suppose you reduce it by two increments of 50, what do you get for SI?

I used a TA of 100 and a CH of 300 for my calculations (also a temperature of 80F which doesn't matter much and a CYA of 30 ppm which does matter -- higher CYA has a larger pH rise). The CH does not affect the pH or the buffering so changes in CH are directly reflected in the SI index. The following table shows the relative change in the SI index as CH is lowered and this applies equally to the cases with and without Borates:

300 ppm CH --> SI 0 (relative starting point)
250 ppm CH --> SI -0.07
200 ppm CH --> SI -0.16
150 ppm CH --> SI -0.28
100 ppm CH --> SI -0.45
70 ppm CH --> SI -0.60
50 ppm CH --> SI -0.74

In this post there was little white stuff at a CH of 70 while at 150 it was showing up a lot. This is all pretty consistent with the SI prediction if one assumes that one gets into trouble when the predicted SI gets to around +0.7 or thereabouts. It does seem to me that the use of Borates plus some minor adjustment of pH, TA or CH for a somewhat negative SI (-0.2 or -0.3) and having a lower CYA level would eliminate this problem for plaster pools (for vinyl pools, a low CH below 100 ppm may be enough), but we'll see.

Interestingly, a higher CYA level has the pH rise more in spite of the greater pH buffering. This is because CYA is a chlorine (hypochlorous acid) buffer so when you add more chlorine to the water that has CYA in it, the CYA resists this change and compensates by raising the pH (basically, more of the hypochlorous acid is removed by getting bound to CYA so reducing the amount of acid in the water has the pH rise).

So if we compare the situation at 30 ppm CYA vs. 80 ppm CYA we have the following where I used 116 ppm TA at 80 ppm CYA to have equivalent carbonate alkalinity (so same rate of outgassing and same initial SI).

NO BORATES, 30 ppm CYA, 100 ppm TA
200 ppm FC --> pH 9.01 --> SI +1.39
100 ppm FC --> pH 8.88 --> SI +1.30
80 ppm FC --> pH 8.83 --> SI +1.27
40 ppm FC --> pH 8.67 --> SI +1.13
20 ppm FC --> pH 8.41 --> SI +0.90

50 ppm BORATES, 30 ppm CYA, 100 ppm TA
200 ppm FC --> pH 8.34 --> SI +0.83
100 ppm FC --> pH 8.23 --> SI +0.71
80 ppm FC --> pH 8.19 --> SI +0.69
40 ppm FC --> pH 8.06 --> SI +0.57
20 ppm FC --> pH 7.89 --> SI +0.39

NO BORATES, 80 ppm CYA, 116 ppm TA
200 ppm FC --> pH 9.35 --> SI +1.64
100 ppm FC --> pH 9.19 --> SI +1.55
80 ppm FC --> pH 9.13 --> SI +1.51
40 ppm FC --> pH 8.85 --> SI +1.29
20 ppm FC --> pH 8.36 --> SI +0.85

50 ppm BORATES, 80 ppm CYA, 116 ppm TA
200 ppm FC --> pH 8.58 --> SI +1.05
100 ppm FC --> pH 8.46 --> SI +0.95
80 ppm FC --> pH 8.40 --> SI +0.87
40 ppm FC --> pH 8.14 --> SI +0.62
20 ppm FC --> pH 7.86 --> SI +0.34

So you can see that the higher CYA is particularly bad if the chlorine level, and hence pH, is very high.

Richard

 

[cruzmisl]

What we need is a Liquidator WS calculator.

 

[Sabot]

Wow… I am dizzy reading all the above!

So to sum it up for us non-technical pool owners, maintaining the proper water chemistry for your pool is the key to reducing scaling with the LQ equipment. Since each pool is chemistry is unique, each pool owner will need to find the right chemistry which will reduce or eliminate scale in their pool. I still believe the LQ operates as promised.

I wonder if one could put together a cheat sheet or a calculator that allows a user to input their chemistry numbers and spits out adjustments? This would be based entirely on the LQ delivery system.

Great posts...

 

[JasonLion]

There is one more bit of information that we need to really understand this system. What is the typical FC level in the water layer inside the LQ under various conditions? The three main variables are going to be 6% vs 12% bleach, how much bleach is in the LQ, and the LQ flow rate. The FC level might also be noticeably higher after the pump has been off for a while.

To measure this will require something like a 9 to 1 dilution (multiply the FC test result by 10) with chlorine free water, or perhaps even higher dilutions depending on just how high the FC really is.

 

[Water_man]

This is a great analysis, Richard, and congratulations for cracking the crux of the matter by advising the addition of borates to control pH rise in the tank.
Just a couple of remarks and one request.

On one hand, from the Langelier SI equation, it’s obvious that CH is not as critical as pH control is for this particular application.
If we look at mrafal’s case, he had CH 450 but uses 50 ppm borates.
If we compare his SI to the one you calculated for 300 ppm CH we get his SI to be higher by only 0.17 as compared to your example.

But then you mentioned ric’s post. He changed CH from 70 to 150 and got a lot more deposits.
This changed his SI by + 0.33. Since this is logarithmic, the effect of raising CH from 70 to 150 is a lot worse then changing from 300 to 450!
However, we don’t have a 100% clear explanation yet, unless ric’s CYA is indeed high (he didn’t post the number.) ric runs CH = 150, pH= 7.2 and had devastating WS issues. My CYA is 60, CH =250, and pH= 7.5 and my WS hasn’t affected performance after 3 weeks work. Why is he so worse off?

Since LQ users may now be interested in adding borates to their pool, please refer to this post in the adding borates thread and see if you can calculate the mixture ratio of Borax/boric acid needed to add borates with no pH effect.

 

[mrafal]

There is one more bit of information that we need to really understand this system. What is the typical FC level in the water layer inside the LQ under various conditions? The three main variables are going to be 6% vs 12% bleach, how much bleach is in the LQ, and the LQ flow rate. The FC level might also be noticeably higher after the pump has been off for a while.

To measure this will require something like a 9 to 1 dilution (multiply the FC test result by 10) with chlorine free water, or perhaps even higher dilutions depending on just how high the FC really is.

I was thinking the same thing. I use 6% bleach and plan to make some measurements this evening.

I'm thinking there may be a gradient to the concentration in the water layer, so I plan to take the sample at the depth of the valve using a turkey baster. (I'll have to sneak that past my wife; she wont like putting it in "chemicals" )

I'd love to know what the scale is on the flow meter. Anyone have any information on the range of flow rates in gal/min?

Marc

 

[JohnT]

Although I'm not big on the chemistry, I thought I'd add some data to the mix.

I have the 8 gallon Liquidator. Started using 6% bleach in it when I installed. My TA is around 140ppm, and CH around 80ppm. I run the pump 11 or 12 hours a day for solar.

After several weeks with 6%, I had a precipitate on the bottom of the tank that was an amber color when viewed through the bleach layer. It moved around a little if I poured the bleach too quickly, and wasn't present in the area near the bottom of the fill funnel. If I poured too fast, sometimes I saw something floating at the boundary between the layers.

I went out of town last week, so I used 10% shock instead of bleach to get a longer fill interval. I let the bleach level get low so I'd have as much NaOCL as possible in the tank. Almost as soon as I started slowly adding the 10%, I began to see the white stuff on the surface of the water in the tank, and some suspended as well. There was so much that I used a piece of a water bottle to skim off what I could and left for my trip.

Now, the precipitate in the bottom of the tank appears to be white. There is nothing on the valves or floating in the water. I'm not sure why the switch to the 10% made the change, but it was fairly quick. I'm sure I added the 10% very slowly, because I had just been reading the posts here about the white stuff. :?

 

[duraleigh]

I'd love to know what the scale is on the flow meter. Anyone have any information on the range of flow rates in gal/min?

Marc, I'm afraid that's the "HASA hope for the best system". I am positive they are simply points of reference and have no real meaning behind them.

JohnT is the second person (I think) to notice a big change between 6% and higher strengths. I am out of town for a few days so cannot help with measurements but I sure hope someone can post up Cl numbers inside the LQ. I'll post mine when I get back.

 

[mrafal]

OK, so I measured the FC in the Liquidator. I used a turkey baster to get a sample near the business part of the outlet float valve. I diluted 10ml of sample with 90ml of tap water. I measured 7 ppm FC using FAS-DPD, so the sample was 70ppm.

I'll take a sample in the morning after the pump has been off overnight and see if it is changed.

For reference, the Liquidator is about half full of 6% Bleach.

It would be useful if someone had a pH meter that could measure the pH directly in spite of the high chlorine concentration. I haven't broken down and bought one yet. This could be my justification (rationalization).

Marc

 

[chem geek]

The saturation index only tells you if you "can" have scale. It does not tell you if you "will" have scale. There are way too many complicated factors in determining the "will" and the "rate". So the analysis I was doing is best seen as a way to hint at possible ways of mitigating the problem, but only experimentation in real LQ systems will tell us if this will work. I think figuring out why Borates can be so effective is the most useful part of the analysis.

As for the 6% vs. 12%, if the gradient of concentration is proportional to the concentration of the chlorine at the bottom, then that would explain a lot since you can see how doubling the FC ppm makes a difference, though it isn't huge but perhaps enough to put one over the edge.

As for ric's post, he not only changed his CH from 70 to 150, but he also lowered his pH from 7.4 to 7.2 so his overall initial SI change was only 0.12 which isn't very much. Of course, measurement errors, especially with pH, can be a factor, but it may be that once you reach a certain critical amount, then the over-saturation can precipitate quite a bit. We'll just have to see with more user's experiences. [EDIT] Of course, that doesn't explain the difference between Water_man's experience and ric's (perhaps TA differences or more likely other factors affecting rate of precipitation including flow rate?). [END-EDIT] Again, I'm most hopeful about the Borates. In fact, the same principle that hopefully helps prevent scaling in the LQ via the Borates also probably works to reduce scale in SWG cells (yet another reason why Borates are helpful in SWG pools).

Richard

 

[mrafal]

One more data point that might be helpful. I set the flow meter to 3, shut off the inlet valve and timed how long it took for the level to drop a half inch. By this crude measure, I get a flow rate of about a 1/3 gallon/minute or 20 gallons an hour.

As a sanity check, I calculated the resulting concentration of of adding 180 gallons (20 times 9 hours of pump time) of 70ppm FC to my 15k gallon pool with 3 ppm and get a scad under 1 ppm. That is certainly in the ballpark of my use. So I would say it is likely that the scale is something close to tenths of gallons/min

Marc