Recent content by chem geek

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...