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Iron Stains


LBuehler

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I have a few questions. Spa has been great. About 6 of us were floating around in it the other night watching the stars it was great!

Ph 7.2

TA 80

Bromine 2

Shocked it yesturday. Spa has been getting a lot of use. Water is slightly cloudy But all levels seem good. Questions: How often do I have to shock? How often do I have to establish a reserve? What can I add to clear the cloudiness. I have some clear and sparkle and some scum buster. Should I be using these products and would they do anything? Would these products have any effect on the Ph or TA levels? Should be recieving my new test kit here in a few days. Thanks

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Bromine level of 2 is too low. Keep it 4-6 ppm. If the spa is left uncovered during the day the bromine will be lost from sunlight. It's the nature of teh beast.

IF your water is cloudy then shock with chlorine (bleach). Shocking should normally be every 1 to 2 weeks depending on use but if you have having heavy usage you might need to shock more often. I suspect your cloudy water is from heavy use and low bromine. However, when you get the new kit post a full set of test reults so we can be sure you don't have any other water balance issues.

All levels seem good tells us nothing. Post test result numbers. You might miss something that someone more experienced will catch from the numbers you post.

In a well maintained spa or pool there shold be no need for clarifiers or enzymes.

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Hey Village. Recieced my new test kit today. Here are the #s

Ph 7.6

Alk 80ppm

CH 20ppm

Br 5.5

According to my charts it had a saturation of .9

What should I be concerned about? At this point in time i think I have almost experienced everything wrong. Tub has been great since our last postings.

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Don'w worry about saturation index. That is for a plaster surface, not fiberglass. I would bring the calcium up to at least 150 ppm up to 300 ppm for fiberglass. I have no hard proof but there seems to be some empirical evidence that higher calcium levels in a fiberglass pool or spa can help slow the tendency to stain.

Other than that, enjoy!

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  • 8 years later...

Hi, really pleased to read the advice to remove the staining from the swim spa. My one is an acrylic shell swim spa and I have a mixture of staining colours. I have refilled it with mains water and added a chelating agent thinking that would remove the staining but it hasn't. I am using silver stabilised hydrogen peroxide called Huwasan at 80ppm. When I add the H2O2 the water goes s tinge of green before clearing after 24 hours. My question is, will ascorbic acid work ok on acrylic swim Spa without damaging it? Also will it work ok if the chelating agent is already in the water? Thanks for your help.

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Get a vitamin C tablet and hold it on a stain. Let us know if the stain disappears where you hold the tablet. I suspect it won't as I suspect the staining is silver and not iron.

You are using a silver stabilized H2O2 as your primary sanitizer (There are several brands),. What country do you live in as in the US (where I am located)  this is not an EPA approved sanitizer for pools and spas because the reaction time against viruses is very slow., although many products are sold that are not EPA approved since in a personal pool or hot tub you can put anything you want in the water, whether it works or not. I base my sanitizer use in what is permitted by law in a commercial pool or hot tub so that is either chorine or bromine. There are other EPA approved pool and spa sanitizers for home use (biguanide/peroxide, copper/silver with chlorine, and copper zinc with bromine) but they are either more work or have slow kill times so I tend to avoid them . Much of the info on the Huwa-san video about chlorine was false except for the fact that chlorine is the most used sanitizer world wide,  but that is not unusual in marketing materials.

What sequestrant did you add? (not brand name but actual ingredient.) Unfortunately, if the stains are silver I know of nothing that will remove them.

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3 hours ago, waterbear said:

Get a vitamin C tablet and hold it on a stain. Let us know if the stain disappears where you hold the tablet. I suspect it won't as I suspect the staining is silver and not iron.

You are using a silver stabilized H2O2 as your primary sanitizer (There are several brands),. What country do you live in as in the US (where I am located)  this is not an EPA approved sanitizer for pools and spas because the reaction time against viruses is very slow., although many products are sold that are not EPA approved since in a personal pool or hot tub you can put anything you want in the water, whether it works or not. I base my sanitizer use in what is permitted by law in a commercial pool or hot tub so that is either chorine or bromine. There are other EPA approved pool and spa sanitizers for home use (biguanide/peroxide, copper/silver with chlorine, and copper zinc with bromine) but they are either more work or have slow kill times so I tend to avoid them . Much of the info on the Huwa-san video about chlorine was false except for the fact that chlorine is the most used sanitizer world wide,  but that is not unusual in marketing materials.

What sequestrant did you add? (not brand name but actual ingredient.) Unfortunately, if the stains are silver I know of nothing that will remove them.

Waterbear, thanks for your advice, I am in England. My wife came back from Asda (Walmart in US) with vitamin C tablets with orange and zinc so when I held the tablet against the dampened stain it fizzed like crazy and turned orange which was not much help so I persisted and rubbed it around for a couple of minutes and I believe it improved the staining. I need to order some proper pure colourless 100% vitamin C tablet or powder from Amazon and try that properly and then report back. We purchased the swim spa second hand on eBay and it is an April 2018 model so not very old, when it arrived the acrylic shell was spotless, like brand new. We have only had it since May and have only ever used this Huwasan sanitizer because we saw a video on YouTube and decided to try going chlorine free. The spa has an ozone an UV system too. After reading your comments I am going to persist and try to manage and if the stains don't improve with the addition of vitamin C on recirculation, I am going to revert to chlorine or bromine. In the meantime if there is a definite improvement with the proper vitamin C tablet, how much should I add per 1000 litres (264 US gallons) of water please? How long should I recirculate for? The chelating agent I was sold is apparently the more environmentally friendly one which is  L-glutamic acid N,N-diacetic acid, tetrasodium salt; GLDA-Na4. I was told to add it between 0.1 - 0.2% v/v so 1 - 2 litres per 1000 litres / 264 US Gallons. At the last fill I added fresh water then the chelating agent, waited for 1 hour then adjusted the pH (it went up from 7.3 to 8.8) then added the Huwasan silver stabilized H2O2 at 80ppm. The water goes a tinge of green for 12 - 24 hours then clears. I am finding that I have to keep adding pH minus to keep the pH in range 7.2 - 7.8. Also I didn't balance the pH for about 4 days due to going away with work and when I got back the staining had got a lot worse and the pH had shot up to 9.2!! Maybe that has something to do with the staining getting worse. Thanks for your help.

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Spent two weeks in the UK last summer (1 week in London and 1 week in Scotland in Edinburgh) and have a close friend that lives in Tiptree who moved to the UK close to 30 years ago. It's a lovely country! Now to business:

IF the stains are iron a few things to know:

1 Ascorbic acid applied directly to an iron stain WILL make it disappear in less than a minute, which is why the vitamin C test is important. If you "rubbed it around for a couple of minutes" and then believed "it improved the staining" still makes me think the stains are not iron. See if you can get some plain vitamin c (ascorbic acid) and repeat the test.

2. GLDA ‐Na4  is about half as effective at chelating iron as EDTA at normal pool/spa water pH range and EDTA is LESS THAN half as effective as HEDP and other phosphonates. All three are broken down by UV light and oxidizing agents (chlorine, bromine H202,  ozone, etc.) so if metals are present in the water the reapplication of sequestrant on a regular basis as well as making sure pH does NOT spike is necessary since high pH conditions are favorable for staining. Likewise, often low pH (but not lower than 7.0 since it can be damaging to equipment) can often lift stains and redissolve them in the water. pH then needs to be brought up slowly by outgassing CO2 (aeration of the water) rather than by chemical means and sequestrant added to help prevent redepositing of stains..

3. Ascorbic acid (vitamin C), Citric acid, and Oxalic acid are all reducing agents and capable of reducing many metal stains (but most effective on iron). They do not work in the presence of oxidizers (pool/spa sanitizers and shocks) so sanitizer levels have to be very low before application. Ascorbic acid is the least toxic of the three and oxalic acid the most but all three are used in commercial pool and spa products for stain removal. Once they have removed the stain pH needs to be kept between 7.0 and 7.4  and sanitizer added in small doses until sanitizer levels are holding. This means that the reducing agent is gone.  Sequestrant also needs to be added. If the oxidizer (sanitizer or shock)  is added too quickly or the pH spikes then the metals can precipitate out as stain again.

4.  Iron stains are normally seen as a yellow to brownish discoloration of the entire surface of the pool or spa below the water line. They are usually not seen as round stains as your picture shows. They can cause a spot stain if a piece of metal such as a screw was sitting on the bottom of the spa and started to rust. Iron stains are essentially rust deposited on the surface of the pool or spa from dissoved iron in the water that is caused to precipitate out on the surface because of water chemistry conditions (high pH and high Oxidizer levels .

IF the stains are not iron then the treatment depends on the metal (manganese, calcium, copper, silver) that caused the stain. To the best of my knowledge staining from silver is impossible to remove and you are using a silver'/H2O2 based sanitizer. Silver nitrate is the most common form of "ionic" silver used in these preparations and Silver nitrate stains most surfaces and can stain skin and hair also. Staining is also a problem in systems that use ionizers (copper, silver/copper, silver/zinc) to 'sanitize' the water. (They have been found to be ineffective because of slow kill times for many pathogens  to used as a primary sanitizer without bromine or chlorine/) This ability to stain (skin and hair) is why silver nitrate is the active ingredient in some lash and brow tinting products in the cosmetology trade and was historically used as a hair dye before the advent of modern oxidation dyes (which cannot safely be used on the lashes and brows). (I know I've gone off topic but I am also very familiar with much cosmetic chemistry).

 

Finally, you gave me a clue when you said that the water turns green for a day when you add the oxidizer (peroxide) and the clears.  The ONLY thing I know of that will make pool/spa water green after adding an oxidizer is dissolved COPPER and copper can plate out in round or irregular stains. Copper stains cam be black, blue, green, tan, or metallic copper color. Copper stains are difficult to remove and sometimes impossible. Best chance at removing them without calling in a professional stain removal service (not sure if you have them in the UK but we have them on this side of the pond) is to drop the pH to between 7.0 and 7.4 and maintain it like that for at least a few weeks while adding sequestrant weekly and if the stains lift drain and refill with water that does not contain copper or other metals, it is better to keep the pH at the low end of the range and do not let it rise above 7.4.

Bottom line, there is no easy way to get rid of stains, no "magic potion", no "miracle in a bottle". It's detective work and trial and error. I gave you some guidelines to follow. I hope something in here is helpful and good luck.

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On 7/17/2020 at 5:15 PM, RDspaguy said:

Just getting the attention of waterbear. He knows chemical issues much better than I. 👍

Thanks waterbear, I live 60 miles north of Tiptree and regularly pass that area with work. Sounds like you had a nice time in London and Edinburgh, they are both great cities. I think I read somewhere in your many posts on here that you are in the Florida area? Never been to the US but am planning on visiting and would like to visit Florida / the south.

That is really helpful information. Since reading your advice I have done the following:-

1. topped up with mains water above the water line to cover the staining completely, checked pH and it was 7.9 so high

2. Added the appropriate amount of chelating agent (I had to use GLDA ‐Na4 as I have got loads of it) and recirculated for 30 mins, tested pH and it shot up to 9.5

3. I then adjusted pH downwards with sodium bisulphate to 7.1

4. Topped up the H2O2 (the chelating agent GLDA ‐Na4 is not compatible with chlorine or bromine) sanitiser to 80ppm

4. Checked pH daily for two days and it kept creeping up to 7.4 - 7.6 so I adjusted it downwards to 7 - 7.1 each day

Today is day 3 and to my amazement the stains have dramatically improved, in particular on the hot tub side of the swim spa which is set at 37 degree Celsius, the swim spa side is at 31 degrees Celsius. The swim spa side is more stained than the hot tub side but is also showing sings of improvement, so temperature may play a part?

At this point I have not added any ascorbic acid and will wait to see what happens over the next few days.

Would you like me to keep you posted on this?

Thanks for your help.

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Definitely keep me posted! Sounds like you are on the right track. Once the stains are removed I would do a full water change (or, at least, several partial changes) with water that does not contain metals if possible. Also, this link contains a link to lowering Total Alkalinity (TA) but it explains why pH rises as a function of outgassing of CO2 and spas hae a constant source of aeration as they run so pH rise is more of a problem.

https://www.poolspaforum.com/forum/index.php?/topic/28846-lowering-total-alkalinity-howto/

I would recommend dropping your Total Alkalinity to 60 ppm or lower to help stabilize the pH but monitor the TA and pH to make sure TA does not drop low enough to cause pH stability problems. If it does raise it by 10 ppm at a time until you find the 'sweet spot' for your setup.

Yes, I had a great time in both places and hope to return on our next trip over the pond. We had a flat in Soho for a week and then a hotel in Edinburgh fro a week. I grew up in S Florida (Miami) but now live in the Oldest City in the New World, St Augustine (North Florida).

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As promised here is my update. I did a complete water change on the swim spa. Refilled with fresh mains water but unfortunately did not get a hose filter to take out the metals and the local spa company said he has never once heard of any customers getting staining problems with our local water in the 10 years he has been in business. He believes there is something suspicious going on with using the H2O2 and like you suggested I consider an alternative sanitiser. I have come off the H2O2 sanitiser and gone onto bromine. I also put in a scale inhibitor and stain removal additive based on etidronic acid which needs adding weekly. Now for the miracle . . . within just 24 hours ALL of the staining has disappeared completely!! There is a reason why mainstay trusted sanitisers such as bromine and chlorine are used. I would advise anyone thinking of running their spa's on H2O2 to not do it as it was very difficult to manage the water and filters and it is now evident that it was also contributing to a staining problem.

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Now I am not getting a bromine reading on my test strips. I have put a floater in with plenty of bromine tablets and have also added granular bromine to try and get things going but despite adding the recommended dose of granular bromine and having shocked with MPS the bromine levels are back to zero every morning. Reading on here it says you have to build up a bromine bank. My question is, is it safe to go in the tub while I am waiting for the bromine bank to build up as long as I add some granular bromine daily? It could take weeks!!

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https://www.poolspaforum.com/forum/index.php?/topic/26324-whats-the-step-by-step-to-bromine-treatment/

Read the entire thread but pay attention to any posts by me or chem geek

IF you have added plain sodium bromide (read the ingredients on your 'granular bromine") then you have indeed created a bromide reserve or 'bank' and adding either MPS or chlorine will activate it into bromine sanitizer (hypobromous acid). It contains other ingredients it is most likely a "one step" bromine product and, in reality, basically a bromine tablet in granular form and it will take time for enough to dissolve to create your bromide bank.

Is your spa covered or uncovered and does it receive direct sunlight? Bromine, unlike chlorine, cannot be stabilized against breakdown by sunlight (UV), which is another reason, besides keeping in the heat, to keep it covered. However, the downside is the accumulation of volatile disinfection byproducts which are known to create health problem. The easy solution is to remove the cover and turn all your jets on high with full aeration for about 15-20 minutes before entering the tub to allow them to dissipate into the air.

Test strips are not the best. My #1 recommended test kit for bromine (Taylor 210) is not available in the UK if I am not mistaken, but Palintest kits are (They are a UK based company) . I am not that familiar with them but they have a colorimeter kits (Pooltest 4 and Pooltest 6)  that would test the parameters you need to test for a bromine spa. You want to be able to test total bromine, pH , alkalinity, and possibly calcium hardness if you are filling with very soft water or hard water. The also have less expensive tests that do not use a meter but rather a color block. The SP 616 tests for bromine, pH and alkalinity would test the basic parameter you need to test. I do recommend testing calcium hardness but it is a parameter that does not change that much so you can have your deal test it every month or water fill.

Hope this helps.

 

 

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