cal hypo and ph

I switched from bleach to cal hypo as my chlorinating source since my CH was somewhat low and Leslie had 100 lb. drums that came out to a lower price than bleach. Since then I have noticed PH levels tend to rise. I am using a basic phenol red test and my cell has 7.6, 7.8, and 8.0 for readings. I had the PH down to 7.2 the other day and with in a week it was up to 7.8 to 8.0. Is the 73% granular Cal hypo the reason? This might just throw off the calcs where it was cheaper if so. :) I am using Leslie power pro "shock" and I just use the powder to chlorinate using smaller amounts daily and 3X normal to shock or what ever the pool calculator says when I check it (most of the time). I can't seem to find Cal hypo pucks other than from Walmart and those seem to disintegrate too quickly and are less than 73%.

Chlorine is being maintained from 3 to 5 ppm.
TA was over 120, I messed up and tried to use test strips at one point, it is now 80.
CYA 40
CH 320 last time I checked. It was below 200 when I started using Cal hypo.
side note for a plaster pool can CH get too big?
12 - 15 K gallon pool.
Pump runs 8 hr. a day.
Also the spa overflows into the pool. Since I usually let the rain fill the pool unless I hear a sucking sound in the skimmer, there is often a 2 to 3 inch drop off from the cut out for the spa to overflow to the pool water line. Could this be aerating the pool?

Also have had a somewhat hidden algae problem. Just cleaned the filter and saw where the algae that some times shows up on the walls was coming from. The DE was green as can be. Put bleach in the filter tank and let it sit while cleaning the filter.
Haven't tested while chlorine was above 6 or so.

I think I have the algae problem solved but I don't know what is happening my filter. Also just discovered the suction is low enough where I can't vacuum from either skimmer. Working on that part but not sure if it is a contributing factor to anything other than the previous algae problem.

The only other chemical I use is hydrochloric acid. I did bring up the CYA level from 30 to 40 recently so some conditioner from Leslie was used.

The particular Cal-Hypo you are using may have more calcium hydroxide in it which is analogous to the excess lye (sodium hydroxide) in bleach so that could account for the faster rise in pH. The higher amount of calcium hydroxide might not be related to the Cal-Hypo strength and is probably more related to the manufacturing process so a different brand/manufacturer might give you better results. Most Cal-Hypo brands have a pH of a 1% solution around 10.4 to 10.8 which is somewhat lower than that of Clorox Bleach (when adjusting for concentrations) -- if you can find an MSDS for your Cal-Hypo and if it says the pH is higher than 11.0 (say 11.5 or higher), then that could explain what you are seeing.

Some of your pH rise, especially from a pH of 7.2 to 7.5 or 7.6, is probably due to your TA level as well as the aeration from the spill-over from the spa, but that would have also occurred when you were using bleach.

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Originally Posted by john509

I am using a basic phenol red test and my cell has 7.6, 7.8, and 8.0 for readings. I had the PH down to 7.2 the other day and with in a week it was up to 7.8 to 8.0.

The lower you put the TA the faster it will rise, Try only lowering it to 7.6 and see how it goes. I would also suggest that you invest in a good test kit, it will save you a lot of money in the long run. Get a Taylor K-2006 (not a K-2005)

Is the 73% granular Cal hypo the reason?
IMHO, no. This is the 'good' stuff. Keep reading.

Chlorine is being maintained from 3 to 5 ppm.
Free or total, how is it being tested?

TA was over 120, I messed up and tried to use test strips at one point, it is now 80.
See my comment above about getting a better test kit. How is this being tested now? You can try lowering it as low as 70 ppm, especially since you are using cal hypo.
CYA 40
CH 320 last time I checked. It was below 200 when I started using Cal hypo.
side note for a plaster pool can CH get too big?
Yes, but you have a way to go.
12 - 15 K gallon pool.
Pump runs 8 hr. a day.
Also the spa overflows into the pool. Since I usually let the rain fill the pool unless I hear a sucking sound in the skimmer, there is often a 2 to 3 inch drop off from the cut out for the spa to overflow to the pool water line. Could this be aerating the pool?
Possibly.

Also have had a somewhat hidden algae problem. Just cleaned the filter and saw where the algae that some times shows up on the walls was coming from. The DE was green as can be. Put bleach in the filter tank and let it sit while cleaning the filter.
This means that you have not been keeping the FC high enough. Once again, how are you testing?

Haven't tested while chlorine was above 6 or so.
Why not?

I think I have the algae problem solved but I don't know what is happening my filter. Also just discovered the suction is low enough where I can't vacuum from either skimmer. Working on that part but not sure if it is a contributing factor to anything other than the previous algae problem.

The only other chemical I use is hydrochloric acid. I did bring up the CYA level from 30 to 40 recently so some conditioner from Leslie was used.
How was the CYA tested?

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I think your problem is more related to testing errors and dropping the pH too low when you lower it (a good acid demand test will help here). The fact that you have an algae problem indicates that there is a problem with either your chlorine testing, your CYA testing or both. You already acknowledged the error in the TA testing.
You also did not indicate how new or old is the plaster in your pool. This could also play a part.
The low suction indicates filter problems. Sounds like you have several things going on here, the rising pH being the least important!

I am using a Taylor kit bought at Walmart now. I am not sure the number because it was rebranded as HTH. The kit is OTO + phenol red. In with it were reagents for CH testing, Alkanity testing, and CYA testing. I ran out of CYA reagent so I bought a bigger bottle of Taylor CYA regent, don't recall refill number at the pool store. I am using 7 mil pool water and 7 mil CYA regent in a shake that and pour slowly til the black dot disappears in the small tube.

I am still using strips to check FC vs. total chlorine but I usually don't find a difference and the strips are giving something close to the OTO readings. I think the algae problem is more from not testing and not adding adding anything during a period of two pretty much back to back to rainstorms. We had a week of pretty heavy rains where I was not fully fulfilling duties. The CL had dropped to 0 and the PH was reading what I thought was 8.2 or higher after the rains. I got a little lazy. Breaking out the vac hose because the sweeper went into the shop also showed me the pump is not circulating as well it should, low suction, so that likely contributed. That part should be scheduled to be fixed today if I don't find anything blocking the impeller or fixed if I do. :)

The chlorine seems to be being used up instead of building up CCs. If there is CC it is not more than 1-2 PPM because that is where CL seems to be dropping to after adding enough to get to 6 PPM the previous evening. I usually test and add near sundown so the CL does not get burned up by the sun. The TC is dropping appropriately so I think the CL is getting used up even if my test strips may be off on this one. I just shocked Friday with 15 PPM added. The TC was down to what looked liked 3 to 6 today the range just below 5-10.

The PH test is phenol red. The comment about not testing when CL is higher than 6 or so applies to PH testing. I have read when the CL is 10 or more the phenol red test is inaccurate. Generally if I go over 6 it is 10 more so I don't bother with PH test until the CL comes back down. 6 really isn't my rule for not testing PH it is just if it over 6 I am probably shocking and it will be over 10.

The alkalinity test is one where you take 25 ml water and drop 5 drops of the reagent and then drop triant a drop at a time until it changes color. Again HTH but I believe that is actually Taylor chemicals which number they don't say though.

I do plan on buying a better kit particularly one that test FC as well as TC. I have not done so yet though.

I also do need an upgrade to check base and acid demand.

I really do not know how old the plaster is. I think the previous owner's son said it was redone a few years ago but I am not sure exactly when. It isn't new and has signs of patching some cracks but it does not look chipped but there are some areas that look kind of gray.

Part of the problem is I was not using the HTH kit for long before switching from bleach to Cal hypo so I have no idea if this was happening before. The strips seem similar in CL ranges and TA to OTO and the kit but the PH was completely unreadable and the ranges on he strips were too big on TA.

Thinking about this, I remembered Leslie advertised some cal hypo "shock" as PH near neutral but not this one. If i can't find the spec sheet I suppose I could test tap water then add a little cal hypo and see how much PH rises. Any idea of how much water to how much powder to use?

Any hypochlorite source of chlorine (bleach, chlorinating liquid, Cal-Hypo, lithium hypochlorite) will have the pH rise when you add it to the water. It is when the chlorine gets consumed/used that the pH drops back down since that process is acidic. The pH neutrality comes from the combination of chlorine addition AND consumption when you end up back to the FC where you started. As I noted, there is a small net pH increase from all of this, but it is usually relatively small compared to the pH rise from the outgassing of carbon dioxide caused by the TA being too high or having more aeration.

As waterbear noted, you need to deal with your algae problem first. As for test kits, get the Taylor K-2006.

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Originally Posted by chem geek

As for test kits, get the Taylor K-2006.

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Couldn't agree more. It will pay for itself over and over again!