Bleach - Ph Issue.

[robquick]

Recently switched to Dichlor/bleach and I'm experiencing real issues trying to stabilize ph levels. I'm in the UK and have not been able to find anything to add borates. Is there anything else I can do control my ph ?

TA - 55ppm

CH - 240

PH - ranging

CYA - 85

Thanks.

[brianthepoolman]

are you using granular dichlor or just regular bleach, if using bleach what is the percentage of sodium hypo-chloride

[chem geek]

A lower TA will less the amount of carbon dioxide outgassing, so pH rise, but it will also have the pH swing more up and down when there is dosing of chlorine and then that chlorine gets used up/consumed. That's why you need an additional pH buffer. If you can't find any boric acid, then another pH buffer that can be used is a phosphate buffer, but it can be messy because it will precipitate calcium phosphate. Such phosphate buffers are often sold in spa stores as "pH Lock" or similar names.

As for boric acid in the U.K., see http://mistralni.co.uk/products/boric-acid-powder-boracic-acid'>this link, http://www.amazon.co.uk/BORIC-ACID-POWDER-CARROM-500G/dp/B0047GQQB0'>this link, http://www.reagent.co.uk/boric-acid'>this link, http://www.intralabs.co.uk/boric-acid/BA400.html'>this link and others by Googling "boric acid U.K." or similar searches.

[robquick]

Thanks, what's the down side in raising the TA? I assumed it needed to be at around 50ppm when using bleach, is that correct ?

[chem geek]

TA is a SOURCE of rising pH since a higher TA has the water be more over-carbonated so there is more carbon dioxide outgassing. See http://richardfalk.home.comcast.net/~richardfalk/pool/CO2.htm'>this chart for how over-carbonated the water is at various TA and pH levels. So when using a hypochlorite source of chlorine, such as bleach, that is net pH neutral when accounting for chlorine usage/consumption (which is acidic), one needs to keep the TA lower to minimize the CO₂ outgassing.

When using acidic sources of disinfectant, such as Dichlor granulated chlorine or bromine tabs or MPS (with silver ions in Nature2) in spas or Trichlor pucks/tabs in pools, a higher TA is needed to offset such net acidity.

So if you find that your pH is stable, you can raise the TA and see if it remains stable. If it doesn't and instead tends to creep up, then a lower TA is better.

[robquick]

Thanks for the links for Boric acid, I was looking on swimming pool sites !!!

What quantity should I buy and how do you calculate what volume to add to the hot tub ?

Do you need to add the acid once on every water fill or maintain a certain level ?

Thanks.

[chem geek]

You can use http://www.thepoolcalculator.com'>The Pool Calculator to calculate dosing. For example, for a 350 U.S. gallons spa, 50 ppm borates would be 13 ounces weight or about 14 ounces volume of boric acid. You just add this once on a refill. It doesn't go away so it will be maintained automatically.

[TdiDave]

At my local dollar store for $2.00

100% Boric acid

[chem geek]

You can read about how boric acid kills insects in http://nisuscorp.com/homeowners/products/niban'>this link and see http://www.youtube.com/watch?feature=player_embedded&v=Jjy3KujkXV0'>this video. Insects are unable to remove boric acid that they ingest, unlike mammals that can excrete boric acid. Boric acid has virtually no skin absorption so the only risk in spas is if one were to drink lots of spa water. I write more about boric acid safety in http://www.troublefreepool.com/are-borates-safe-to-use-t14750.html'>this thread. With an EPA margin of exposure (MOE) safety factor of 100, a 100 pound person would need to drink a little over 5 tablespoons of spa water every day for a lifetime to reach the highest no observed adverse effect limit (NOAEL). Without the factor of 100 safety factor, you'd have to drink over a gallon a day.

[robquick]

Chem Geek,

The price of Boric acid appears to vary significantly, should I go for the cheapest or are there other things to be aware of ?

What's the best way to reduce TA, can I use PH reducer or do I need a different chemical ?

Thanks.

[chem geek]

You can use the cheapest source of boric acid, assuming it is close to 100% purity. They shouldn't vary in quality and you don't care about the degree of granularity since it dissolves fairly quickly.

As for reducing TA, it's a process of acid addition with aeration all done at a low pH as described in this post.

[robquick]

Hi,

Apologies for my lack of understanding however, I'm getting a little confused with my rising PH issue as much of the information above is some what over my head ! I would appreciate some guidance on the following questions.

Is there any other method to try to control my PH other than using Boric acid ?

What's the risk of adjusting my TA (currently 77ppm)?

Do I increase or decrease TA to help stabilise PH ?

I have to reduce my PH every 3-4 days (rises from 7.3-7.9 over this period) am I making a mountain out of a mole hill or should my PH be more stable than this ?

I'm reluctant to use Boric acid as I've got no method of measuring the PPM which worries me, am I over reacting?

When looking at the retailers that sell Boric acid in the UK, the websites talk about granules or powder does this make a difference ?

Any guidance appreciated.

Thanks.

[chem geek]

Is there any other method to try to control my PH other than using Boric acid ?

I presume you mean the other than the combination of lowering the TA and using boric acid. The other approach to pH control is using a phosphate buffer, but that can get messy since it precipitates calcium. Some spa products that use a phosphate buffer sometimes say things like "pH Lock". Read the labels for ingredients.

What's the risk of adjusting my TA (currently 77ppm)?

If you only lower your TA and you don't use boric acid then your water will be more susceptible to pH swings from chemical additions such as chlorine. Though with a lower TA the tendency for the pH to rise will be less because there will be less carbon dioxide outgassing, there will be less pH buffering to prevent the pH from changing when other chemicals are added. That's why boric acid is used since it is a pH buffer that doesn't cause a rise in pH.

Do I increase or decrease TA to help stabilise PH ?

The answer depends on what is normally happening with your pH. If your pH tends to rise over time, then lower your TA. If it tends to drop over time, then increase the TA. The pH may drop over time if you are using net acidic sources of disinfectant or oxidizer such as Dichlor or bromine tabs or non-chlorine shock (MPS). The pH will tend to rise if you use hypochlorite sources of chlorine such as bleach, chlorinating liquid, lithium hypochlorite or Cal-Hypo (the latter not usually recommended because it increases Calcium Hardness). However, the rise is not so much from the chemicals as from carbon dioxide outgassing and that is minimized by lowering the TA level.

I have to reduce my PH every 3-4 days (rises from 7.3-7.9 over this period) am I making a mountain out of a mole hill or should my PH be more stable than this ?

The pH will tend to rise more quickly when it is lower because the water is more over-carbonated at lower pH. See this chart to see that a lower pH and higher TA is more over-carbonated. So you normally wouldn't try to lower the pH so much to 7.3 and would instead target something more in the 7.5 to 7.8 range. Your pH should be more stable than you are seeing and the reason it isn't is partly due to the higher TA and partly due to not having borates (boric acid).

I'm reluctant to use Boric acid as I've got no method of measuring the PPM which worries me, am I over reacting?

The level of borates won't change over time so if you dose it properly you should be fine until you drain/refill to change the water.

When looking at the retailers that sell Boric acid in the UK, the websites talk about granules or powder does this make a difference ?

I don't know if it makes a difference, but some reports on pool forums say that the powder can tend to cake up on the surface of the water so take longer to dissolve than the granules. It's also best not to breathe in the boric acid so I would presume that the granules are less likely to get blown around with wind while you are adding them.

[robquick]

Is it worth me reducing my TA to help control my rising PH then?

If so, what TA would you aim for?

Am I right in thinking I can do the above by using PH reducer (which I think will reduce TA and PH) and then us PH increaser to raise PH back to the correct level (and will not increase TA)?

Is there a downside to low TA?

As usual many thanks for the great advice !

[chem geek]

Is it worth me reducing my TA to help control my rising PH then?

Yes it is, so long as you have another pH buffer such as borates (boric acid).

If so, what TA would you aim for?

50 ppm, at least to see how that goes.

Am I right in thinking I can do the above by using PH reducer (which I think will reduce TA and PH) and then us PH increaser to raise PH back to the correct level (and will not increase TA)?

No, you do not use pH Increaser. You use a combination of acid addition with aeration of the water all done at low pH (around 7.0). Acid lowers both pH and TA while aeration only raises the pH with no change in TA. So the combination lowers the TA.

Is there a downside to low TA?

No, not so long as you have a supplemental pH buffer such as borates (boric acid). If you had a plaster surface or grout, then you'd want to increase the Calcium Hardness (CH) to have the calcite saturation index be closer to 0 to protect such calcium carbonate surfaces, but that isn't needed in an acrylic spa.