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The boron-doped diamond electrodes are more than a regular saltwater chlorine generator. They do not just produce chlorine from chloride salt. They also produce hydroxyl radicals that are very powerful, though very short-lived, oxidizers. Think of it as an ozonator on steroids. The downside...

Are you able to maintain the bromine level in the spa just using a bromide bank and having the ozonator create more bromine from the bromide bank? If so, then just adjust the filtration on-time that presumably has the ozonator on to be long enough to maintain a bromine level in the spa. If you...

See Calcium Nodules in Pools. It's primarily due to a defect in workmanship where a void was created between the plaster surface and the gunite below -- that is, a bad troweling job in some places. The problem may not show up for years -- in my pool it started to show after around 7 years...

It'll depend on what FC level keeps away algae in this particular pool. If it's only a few ppm above the normally recommended level, then that's not very much more chlorine. If it requires closer to a 15% FC/CYA level such as may be required for yellow/mustard algae, then that would be double...

That is simply not true that operating at a higher FC at the same CYA will use the same amount of bleach. The loss is roughly proportional to the FC level for a given CYA level. If you maintain double the FC at the same CYA level you will lose roughly double the amount of chlorine and this...

So there is +/- 0.5 ppm for the 10 ml sample size it looks you are using, but it's clearly using up more chlorine initially at around 2 ppm FC dropping to 1 ppm or less at the end. The 2.5 ppm between Thursday and Friday is a blip but may really be 2 ppm and perhaps was a sunnier day. I...

It happens in standard chlorinated water, not just in a pool. If you look even at George Clifford White's "Handbook of Chlorination and Alternative Disinfectants", you will find all kinds of inconsistencies even in pure water with only chlorine added. There is no ammonia or organics added so...

That's not usual. Usually during the day one loses more chlorine at higher FC levels, CYA held constant. The loss is roughly a percentage loss. This is why the daytime losses when doing a SLAM are much higher than at normal FC/CYA levels. For your 19 to 4 in a week (which by the way would be...

That's an excellent document. While the information on the pH electrode is excellent and indeed pH electrodes follow the Nernst equation such that pH (negative log of hydrogen ion activity) and voltage are linearly related, that is NOT true for real ORP sensors. The RT/nF that they call the...

This is one area where even the manufacturers are forthcoming in the need for regular maintenance of ORP (and pH) probes. See the Hayward Sense and Dispense manual: or the Pentair IntelliChem Water Chemistry Controller manual: Both manuals also say to "Always test water chemistry with a...

Full-strength Muriatic Acid (31.45% Hydrochloric Acid) has a high vapor pressure at higher temperatures. This paper and page 2-76 in this paper show that the vapor pressure of the acid at 40ºC (104ºF) is about 81 mm Hg or about one-tenth of an atmosphere pressure. Water vapor pressure adds...

There's a pool service called PoolChlor that does this (or used to do this) where for some pools they use a combination of chlorine gas and chlorinating liquid (but for chlorine gas you need special permits). 14 ppm FC with 100 ppm CYA has an active chlorine level of roughly 0.14 ppm FC and is...

This would cause corrosion from inside the flue pipe which is why I described that as a possibility but not likely given that it looks like the corrosion he is seeing seems to be outside all piping. Would the process you describe have corrosion on the outside or only on the inside? You are...

The phosphate remover should let you operate at lower FC/CYA levels or for your pool the normal levels and not get algae growth. Even if you have significant phosphate levels in your fill water it will take time for that to climb unless you have very high amounts of evaporation and refill...

No, chloride and chlorine are the same element, but their oxidation state is different so you can consider them to be different chemicals. Chloride is the same as found in sodium chloride which is ordinary table salt. It is essentially innocuous unless it gets to very high levels at which...

Welcome to TFP! :wave: If your bromine level is high then you may be getting a false pH reading in Taylor test. Try temporarily lowering the bromine level to 6 ppm or lower and see what happens with the pH test. If they are still different, then your pH sensor may need cleaning and...

During a SLAM you can use a 5 ml sample size where each FAS drop represents 1 ppm. That will save on reagent. For normal testing, using the 10 ml sample size for 0.5 ppm resolution should be sufficient. The OTO test can be hard to read, but I hear you regarding the cost of getting the FAS-DPD...

The reason for the higher CYA target for SWCG pools is not just that it saves money by losing less chlorine to sunlight, but the lower SWCG % ontime means that the rate of pH rise should be slower as well. So it's not just the saved money from lower electricity cost or even from using less...

Welcome to TFP! :wave: Since the rust is on the outside of the pipe (see if you can look inside the pipe to see if the rusting is less, the same, or more), I suspect it is caused by the external environment. One possible cause is chemicals are stored in the same room as the heater, such...

Yes, that should be fine. The active chlorine level is lower at lower temperatures (for the same FC/CYA ratio) and there's less sunlight on the pool so a higher CYA isn't needed. You can raise it higher when you open in the spring.

So if the TA settles to some amount where acid addition isn't lowering it, then that means that either the amount of TA being added from evaporation and refill is matching that lowered from the acid addition or that the pH rise is not from carbon dioxide outgassing (or a combination of these two...

Thanks for the feedback. We know that UV will deplete both chlorine and bromine, but good to know that this happens in real-world situations in spas. We've seen this before with chlorine, but your situation confirms that the same problem occurs with bromine as well.

It sounds like this micro-biologist does not understand the chlorine / Cyanuric Acid relationship. That's understandable since CYA is not normally found in the natural environment especially with chlorine. It's added either separately or as part of stabilized chlorine products (Trichlor or...

Most of the pH rise in pools either using a hypochlorite source of chlorine or using a saltwater chlorine generator is from carbon dioxide outgassing because the TA is set too high or the pH too low. Try lowering the TA to 70 ppm and target 7.7 as your pH and see if things improve.

When plaster is cured it produces calcium hydroxide, but during curing the water is supposed to be saturated (or even somewhat over-saturated) with calcium carbonate and the calcium hydroxide as a result should get converted to calcium carbonate in place. That "seals" the plaster. Marcite is...

The limit to shipping TF-100 is ONLY for Canada due to an exclusive distributor relationship with Taylor in that country. The reason the TF-100 is not shipped to other countries (other than Canada) including Australia has nothing to do with any relationship with Taylor, but with the complexity...

So 26 gallons of acid for a 17,000 gallon pool since January is 2.4 gallons per month or a little more than 1/2 gallon per week. It's understandable to add a lot of acid soon after a replaster with most being added in the first month but then should noticeably trail off over the next months...

Proper plaster curing does NOT result in any CH increase. Instead, the calcium stays in place in the plaster and bicarbonate in the water is exchanged with hydroxide. If CH is increasing due to the plaster, that is bad and means that your plaster is dissolving calcium carbonate into the water...

Technically, the issue is the low pH and its effects on a copper heat exchanger. The pH isn't actually terribly low so the advice is conservative. Also, if one has a titanium or cupro-nickel alloy heat exchanger there is less risk. In your case with no heater there should be no problem at all.

It only goes away if there is something in the pool to oxidize. The MPS lasts longer than chlorine if there is nothing to oxidize in the pool. Of course, with reasonable bather load, the MPS should get used up in hours as you say. The problem is that you can never know for sure. However, in...