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If the surface was composed of some calcium carbonate, then if that were dissolving into the water it would raise pH, TA, and CH. If you add acid to compensate for the pH, then you still have some TA rise and of course the CH remains higher. For an initial dissolving that increases CH by 10...

Yes, you are right. I was thinking the pellets partially stayed intact and fell into the water, but it sounds like that's not the case.

You can always use rain overflow to dilute your water and keep CYA in check. And you can always raise your FC target if your CYA level is higher. There are no absolutes such as never using Trichlor. You just need to understand and deal with the consequences. Some pools with short seasons and...

As I noted in my post in the dry ice thread, "Adding one pound of dry ice to 10,000 gallons would drop the pH from 7.5 to 7.0 if the TA is 100 and if all of the gas dissolved in water." When I added leftover dry ice in my pool, I registered a pH drop consistent with about half the amount I...

Well, I converted prices to price per weight and then compared by chlorine content by weight. I could have done the same thing by volume instead but most products are sold by weight. The exception is the chlorinating liquid or bleach which are sold by volume (i.e. $/gallon). Ultimately, you...

Dry ice in the pool water will lower the pH with no change in TA. Not all of the CO2 will outgas. Some will dissolve in the water. See the thread 60 Pounds of Dry Ice and a Swimming Pool!.

For one week, using Trichlor pucks and possibly raising the FC level usually works well. For two weeks, that is harder but if one has an inline chlorinator of sufficient capacity and sets its output appropriately then they might be able to get by with 2 weeks. The CYA level may rise more over...

Those prices are pretty old, but their relative relationship shouldn't be too far off. The 12.5% is Trade % which is the VOLUME % of available chlorine. For the comparisons I used the normal definition for % Available Chlorine which is a WEIGHT %. The difference is due to the 1.16 density of...

Use the directed amount on the MPS bottle or instructions. It may or may not help get rid of existing CC. It all depends on what the CC is. Unfortunately, CC can be many different types of chlorinated compounds. If it were monochloramine, then that is most easily removed by chlorine so...

In theory, yes, but in practice not necessarily. It all depends on the source of the CC. MPS oxidizes some chemicals before chlorine gets a chance to form CC, but that's not the case for ammonia and probably not for urea either. So using MPS can be hit or miss. It can certainly be tried...

Well I don't know why there's a difference between last time and this time, but I do know that 50 ppm Borates will help buffer the pH so you can get boric acid from DudaDiesel or from The Chemistry Store.

It's not for soaks in the 90s, but many people only heat up their spa to the higher temperature when they are going to use it. I think your low CYA has more to do with the more rapid loss in chlorine. The higher temperature doesn't help not only because of the more rapid reactions, but there...

Did you have borates in the water before? Do you have more aeration now than before?

The 25% 24-hour loss in a spa with no ozonator nor UV is at the usual spa temperatures people keep which in between soaks is typically in the 90's. For typical chlorine reactions, they double in speed every 13ºF so it's possible the higher temperature explains what is going on except there...

See this post for chemicals names for each reagent. Matt's description of the iodide reaction is not correct. Iodide is easily oxidized even by chloramines so the free chlorine and the chloramines react with iodide to form iodine. So both free and combined chlorine are consumed (the combined...

Draining before is more effective because you initially remove high CYA water. If you don't drain before and the water level rises but does not overflow, then subsequent evaporation will return things to exactly as they were before. Even if there is rain overflow, you will remove very little...

Yes, I think that's because there are some regulations in Canada for the more pure granular sodium bromide which is why you can't normally find it. There is this link for 98% sodium bromide from a Canadian spa retailer.

If what you are talking about is a thin foam sheet that sits on top of the water, then that's mostly to cut down evaporation to slow down how much water gets absorbed by the hot tub cover, especially when it's water-blocking layer gets broken down. Heat insulation should primarily be from the...

The pH will naturally be higher in colder water so it is perfectly reasonable to target a higher pH as the water gets colder. That keeps the water closer to being in balance for plaster surfaces. Colder water won't react as quickly so the risk is lower with a lower CSI but nevertheless it's...

I don't know what kinds of consumer bacteria test kits you've got. They aren't even that common in the U.S. but there are some (e.g. Watersafe drinking water and Watersafe bacteria test strips test for E.coli and many other fecal and non-fecal bacteria).

I think you should give the folks at Ahh-Some a call about this. Even if you had overdosed, a complete drain/refill should dilute things enough to not have so much foaming. Let us know what they say. For regular foaming (not what you are seeing), having the CH at around 120-150 ppm is usually...

Thanks for the details. Makes more sense to me now. I suspect the fading was from the Trichlor granular added directly to the pool and settling on the floor.

The active chlorine level when the FC is at SLAM level which is about 40% of the CYA level is the same as in a pool with an FC of 0.6 ppm with no CYA so less than found in commercial/public pools. Nevertheless, as my wife can attest to after swimming in an indoor community center pool every...

Probably fairly safe when the pumps are off, but when they are on they may aerosolize whatever this material is and if it's some kinds of bacteria that can be a real problem. Not likely, but biofilm isn't good to have. Legionella is rare, but not something to mess with. If it's just...

For chlorine, one can use hydrogen peroxide to neutralize, but I don't think that works well with bromine since the hydrogen peroxide may create more bromine from the bromide bank. Running the jets with the cover off should outgas some of the bromine. Having bather load would use it up but...

That's odd that the section of the liner that has faded is at the bottom. That would happen if there were manual chemical addition in the same place without good mixing where the concentrated chemical fell to the bottom so bleached out the liner. I wouldn't expect that from an SWCG even if...

Most people just start with 1-2 ppm FC and if it goes to zero during a soak then the monochloramine that is formed will still have some slower disinfection. For commercial/public spas you'd want the active chlorine level in the water at all times, but for residential spas the risk is lower...

This one is what you want and is at a ood price at Newegg.

Re: Newb with bromine tub You may have put in too much bleach. Also, I think you forgot to add a bromide bank by adding sodium bromide (1/2 ounce per 100 gallons) to the tub. Eventually the bromine tabs will add enough bromine to form a bromide bank, but usually you want to add sodium bromide...

Don't forget to start out using Dichlor until you build up the CYA level and then you switch to using bleach. The reason the spa dealers freak out about bleach is that if you were to use only bleach then the chlorine would be too strong/harsh on your spa. By building up CYA with Dichlor (or by...