Retep

Feels great taking the leap at -20C. Make sure to drink those Labatt Blues quickly before they start freezing outside. . . Cheers

Very interesting. Thanks again for all those links.

Thanks for all those links. Very , very interesting indeed. I just looked at them quickly and will read them through later on. As I mentioned in my posting above - I love to learn new things.

chem geek- I do disagree with you on that one I still believe that ORP readings are an excellent indicator how "germ - free" your tub water is, regardless what your Chlorine Level is in your spa. Of course you are right when you say it will vary by manufacturer, however it still serves as a "helping parameter". As we all know the FAC effectiviness is also very much dependable of the pH. If I want to achieve an ORP reading ( for example) of 750 mV only 0.6ppm at a pH of 7.2 would be sufficient. If the ph is 7.8 we need around 2 ppm in order to have the same effectiviness from our Chlorine . (Those figures are based on a public pool, where the water temperature is much lower - I assume we need a higher chlorine levels in spas due to higher water temperatures). Public Pools / Public Spas have usually an automatic controller which inject Chlorine / and/or Acid when there is a demand for it. Those controllers work either through ORP readings or so-called Amperometric units. ORP controlled units takes a very long time to react , for this reason it is preferable to use automatic controllers which work Amperometric. On those the operator sets the Chlorine level at ( for example 1.5ppm) and if it drops below,Chlorine will be injected till we reach the desired 1.5ppm. Even those units have ORP readings, but these are meant as an additional "helping parameter" So - and now the Original Poster makes me go into my tub with my little hand held ORP meter to make my own little experiments. Thanks a lot - the Olympics are on and I have to do tests in order to satisfy your ( and mine) curiosity I'll report later with the results Cheers

No doubt that ozone is very powerful oxidiser. I guess the amount of ozone which residential spas produce is very little - therefore I would not be too worried about having ozone residuals in the spa water. Commercial Ozone water treatments for public pools have to be "de-ozonised" after the water passes through the Ozone generator. This is usually achieved with a activated carbon filter, which removes the Ozone before returning to the Pool. It used to be the "Hype" about 10 years ago in Europe, but in the meantime it showed certain drawbacks as well. Fairly expensive to purchase, repairs, high electrical consumption being some of the disadvantages. The newest , latest "Hype" ( which is also fading rather quickly) is UV radiation, which unfortunately produces high THM's. Meanwhile the public pool engineers in Europe are going back to the basics: Good vertical sand filters, slow filtration speeds ( max. 6 gal/min/sqft), and proper coagulation/flocculation.

I second that The other day I happened to listen to a conversation what a sales guy at the local pool/spa store told a client who brought in a water sample. . . . Next thing you know the client got talked into buying stuff which boggled my mind. I guess its all about profit and sales people at the stores are pressured by the owners to sell as much / many chemicals as possible.

I was always under the impression that CYA has only one purpose , -> protecting the Chlorine from UV degration. The other 2 functions (buffer the power of chlorine and reducing outgasing / evaporation rate ) are new to me. Not saying that's not true - I guess I have to do more research on that. My prevoius house had an outdoor pool , which was exposed to sunlight and I would keep a level of around 30 - 40 ppm CYA in the pool. Mind you - this was a pool with about 14.000 gal with a very light bather load. I'd keep my FAC at 1-2ppm. Hot tubs are much more "dangerous" than slightly used private pools in terms of keeping them microbiological safe. We all know that if ( for example) 3 people enter the tub and stay in there for 30 min. the FAC level drops quite fast. For that reason I prefer having about 3 ppm in the tub before people use the tub. I rather have a bit of chlorine "reserve" in my tub then getting (amongst other things) legionella problems. Again - for this reason it is (to me anyway) important to monitor my ORP's in the water. If I got more than 750mV I am assuming that no cross contamination can take place, regardless how high ( or low) my FAC is in the tub. Found an article about CYA , which demonstrates the relation between ORP and CYA -> http://www.texaswaterworks.com/overstabilization.pdf Disclaimer : We all know that not everything we read/find on the net may be true or accurate. For my part I love to learn new things and I guess we learn every day.

I don't get lots of sun in my spa to start with. If I would then I would keep it at minimum levels, since CYA makes your FAC less active ( to put it in simple terms). Chem geek explaines it quite well on the 3rd posting : Quote: "Why don't you try using Dichlor for a while and see what happens to the ORP reading at the same FC and pH levels? I think you will be in for a surprise as the CYA builds up and the ORP goes down substantially at first." In other words : You would need more FAC when using CYA in order to achieve the same ORP's. In regards to your second question : I am using a Photo Spectro Meter in order to give me exact readings. Here I am using also DPD 1 ( for FAC), DPD3 (Total Cls) and a DPD 2 Tablet for Monochloramine. This kit also has special drops for measuring Chlorine dioxid ( which I also use for my tub ). In this case the Chlorine dioxid acts as my oxidiser - usually 0,2 ppm is sufficient ). Additionally I am using a Turbidity meter - lowest level in my tub was 0.09 NTU. For public swimming pools I use a flocculation / coagulation process (when using Sandfiltration) , Chlorine for sanitation and a modified chlorine dioxid process which prevents (re)formation of chlorite and chlorate. With this water treatment process it is possible to achieve microbiological safe healthy water by using less than 1 ppm FAC, very low combined ( < 0,2ppm) and superior turbidity ( as low as 0,03 NTU ) , THM levels less than 15 ppb and ORP levels between 750 and up. Spas are a bit more problematic though ,due to cartridge filtrations where proper flocculation/ coagulation can not really be used

No - I am not using cyanuric acid ( and never will). Calcium hypochlorite 65% and muriatic acid to bring down the pH. Thanks for the nice write up chem geek. If I understand correctly there is a difference between different manufacturers of ORP Meters. Anyhow - as stated before I should be ok as long I am above 750mV. Naturally I try to keep my FAC never below 1 ppm. After I posted my initial post I did go into the tub ( my son left after 20 min in there)- I stayed for about 30 min - turned jets on - water temp at 101F. 10 min after getting out of the tub I took another test and got the following results : pH=7.18 , Free Cl2 = 0,16ppm , Monochloramine(DPD2 Tablet)= 0.28ppm , Total Cl2 = 0.5 ppm ; ClO2= 0.1ppm. ORP dropped down to 681mV.

Hi everyone, First time poster here - found this forum by googling . Thought I share a bit of my experience here ( in case somebody actually really cares. . Got one of those portable ORP meters and did some tests on my tub. ph was at 7.5 ; FAC = 4.98 ; Total Cl2 = 5.03 ; ORP = 775 mV Lowered the ph to 7.11 and the ORP went up to 828 mV. 24hrs after I tested the water again : ph = 7.16 ; FAC dropped to 1.50 ppm ; Total Cl2 =1.73 and ORP was still at 779 mV. 750 mV should be sufficient to keep my water microbiologically safe - looks like I don't need more than 1.5 ppm FAC providing I keep my pH between 7.1 - 7.2 Anyone else tested their water with an ORP meter ?