Solution to brown water in pool/yellow water from well

[frankinbahia]

I'm posting this in the Just Getting Started forum since most of the questions I've seen re problems with brown water in the pool and yellow water in a well that feeds it seem to be here.

I'm a newbie to TFP and certainly no chemist, but I have considerable experience with well water since that's all that I have (for both house and pool). If you are using well water and your pool water starts turning brown (and you haven't had a recent mudslide!), this may help.

The typical problem starts with the pool water turning brown (but not turbid), often after adding a heavy dose of chlorine. If your well water is faintly cloudy or yellowish, it's likely caused by dissolved iron, and mechanical filtering (like your pool's) can't remove it. There are only two ways to get the iron out: with an aeration system (expensive) and with aluminum sulfate (cheap). I've used aluminum sulfate for years with no problems.

When I first heard of the aluminum sulfate method, my first concern, of course, was safety. Can you really drink that stuff? It turns out that most municipal water treatment plants use aluminum sulfate, to remove dissolved material, so if it isn't safe, millions of people around the world are in trouble.

While the proper dosage depends on the concentration of iron (determined with readily-available test kits for well water), I've never needed more than 100ml (or about 1/2 cup) per 5000 liters of water. The chemical is sold in fine granular form and is added to the pool as follows:
- turn the filter on
- in a bucket, mix the aluminum sulfate with some pool water until it dissolves. (There will be a little residual grit that doesn't dissolve - no problem.)
- add the mixture thru the skimmer or in front of a return
- after a 1/2 hour, turn the filter off and leave it off for 12 hours. (This 'calm' time is very important.)
- when you come back, the bottom of your pool will be as brown as the water was. That's the iron that was pulled out by the chemical and sank to the bottom
- carefully vacuum out the iron

I think it's a good idea to do this treatment any time you add significant amounts of well water with iron in it, rather than letting it build to the point that the pool water turns brown.

 

[Patrick_B]

I have not encountered this method, but I don't work in municipal water either. We do however have a chemist type around here who will elaborate on this more. He goes by chemgeek, and his name is Richard.

Interesting post and welcome to the forum.

 

[JohnN]

Very interesting post. I can't wait to hear Richard's thoughts on this. It certainly would be better than my solution, which is to just let the filter get it.


Sent from my iPhone using Tapatalk.

 

[connie]

Where do you buy the aluminum sulfate? I too have well water. Can you also add this to your well to help rid the iron prior to it coming into the house and is it safe to drink?

 

[frankinbahia]

I buy aluminum sulfate at my pool supply store. (I live in rural Brazil, where well water is common -- not sure if it's as readily available in more developed areas.) Any yes, I use it for my household water. As I mentioned, this is often used by municipal water treatment plants, and everything else I've been able to find on the internet suggests it's safe.

 

[Patrick_B]

How do you treat your household water with it?

 

[duraleigh]

Aluminum sulfate is a flocculant. Flocs get VERY mixed reviews from users. Some work, many don't, some cause more problems than you had.

 

[frankinbahia]

Re brushpup's question: I have to use two holding tanks, each 5000 ltrs. In the evening, the pump for the 'treatment tank' turns on automatically to refill, I throw in a 1/2 cup of the chemical, and the pump shuts off wihen the tank is full. In the morning, after it's rested and the iron has settled overnight, it can pump to the other tank which directly supplies the house. The buildup at the bottom of the 'treatment' tank needs to be cleaned out once a year. I know this sound very Rube Goldberg, but it works!

 

[Patrick_B]

Ahh OK. Great if it works in your house and your pool too. Here, we don't don't advocate the use of flocs or clarifiers...hardly ever because they often cause more problems than a person had before.

 

[chem geek]

Ironically, there are iron flocculants as well as aluminum flocculants. Some water treatment facilities use ferrous sulfate that chlorine then converts to ferric form and at appropriate pH flocculation occurs. So if it were not for the risk of metal staining in a plaster pool, one could floc the iron directly. So if you are to use an aluminum floc you need to 1) do so before adding chlorine to the water otherwise you'll create ferric compounds defeating the purpose of avoiding their staining potential and 2) need to adjust the pH for maximum flocculation which for alum flocs is usually a lower pH such as 7.0 or 7.2.

As described in this paper, an alum floc will partially remove iron by 18-75%, but pre-oxidizing by potassium permanganate results in 99% elimination of iron, but the pre-oxidizing could cause staining of plaster surfaces. So it sounds better than nothing, but not a guarantee. It probably just gets the iron level down to something that is more manageable.