Iron won't settle in chlorinator tank

[Mikey]

I've got a deep drilled well that produces really disgusting water. Smells bad, tastes bad, but passes health department tests. I suspect bacterial iron among other problems, but that theory was poo-pooed by a local well expert (appropriately named "Rusty").

It gets chlorinated via a Pulsafeeder pump just before going into a 125 gallon settling tank. However, the oxidized (I assume) iron remains suspended in solution. When I open the drain at the bottom of the tank, a brief shot of rusty water comes out, but then runs clear. About once a year I remove the tank and pressure-wash it, but I've never seen any sign of iron buildup.

The problem is, of course, that the suspended iron gets passed on to the carbon filter, resin tank, and house. I put in a couple of filters (one stainless steel mesh to get out the big pieces, one cheap spun filter) which help a lot, but we still see iron buildup over time on the bottom of the dish drainer and other places where small amounts of water accumulate and evaporate over time. Other than that, the resulting water doesn't smell, looks clear, seems OK, tastes good.

I asked Rusty if there was a better filter I could use, but he suggested I just add soda ash to the chlorine tank to adjust the pH. Didn't help. He doesn't seem anxious to take any of my money.

At this point I'm thinking of replacing the cheap spun filter with one of the big blue jobs, but would welcome any suggestions.

[Bob NH]

For reasons that I won't try to explain here unless asked, the effectiveness of a settling tank is related to the plan-view area of the tank and the settling velocity of the particles. Since iron particles are small unless coagulated, they settle slowly. A round tank that is 4 diameters long is 5 times as effective as a settling tank if it is laying on its side as it is if it is upright.

Your settling tank is probably useful as a retention tank to let the oxidation process take place, but probably not as a settling tank. That is confirmed by your experience.

Where you are getting lots of colloidal iron, I would try inexpensive cotton string-wound filters. Cotton tends to expand when wet and becomes more effective with use. I use the tightest wound cotton filters that I can get to meet requirements for removing giardia, and they hold a lot of dirt before getting plugged.

The pleated 1-micron cartridges that I use in the Big Blue housings do a great job of removing crypto and that sort of stuff but are more expensive than necessary for removing iron particles and don't have as long a life on a gallons per dollar basis for removing ordinary suspended material.

What kind/how big/how many housings do you now have? You could probably try the cotton filters.

[speedbump]

A backwashable iron filter is what you need. That should have been the first unit after the retention tank. Instead, you are gumming up your carbon. I hope that carbon filter has a backwashable head. The iron that gets through the carbon will also help gum up the resin in your softener.

bob...

[Mikey]

My tank is about 6' tall and maybe 18" diameter -- roughly the 4x tank you mentioned. There's a 200-mesh Rusco spin-down filter at the outlet, followed by a 10" filter which currently has a cotton-wound element in it; they seem to last about 60 days. Our average usage is 125.5 gpd, which includes water used for backwashing.

The carbon filter is backwashable. It's a fiberglass tank about 5' tall, 10" in diameter, same as the softener resin tank. I'm pretty sure the heads are Fleck, but there's absolutely no manufacturer's identification on them. I can post a picture tomorrow if necessary. I'm pretty sure it's set to backwash every 6 days. I had the carbon filter rebedded about 3 years ago, and at that time it seemed pretty filled up with iron. Softener resin has never been changed since installation, maybe 8? years. Probably time to rebed them both?

What kind of backwashable iron filter do you recommend?

The city (pop. 1700) is making annexation and water & sewer noises, so I don't want to spend huge bucks on this if we have to shut down the well soon. OTOH, we want good water, and a few hundred bucks more is a drop in the bucket (so to speak) in the grand scheme of things.

Whatever I do, I need an Idiot's Guide to Managing Your Water System. I have no clue how often these things should be backwashed, what the residual chlorine level and pH should be coming out of the settling tank, etc. Installer gave me a swimming pool test kit marked where he says things should be, but I have a hard time distinguishing the colors very well. Local extension office hasn't been much help, nor have local water guys, who all want to sell a new system.

[speedbump]

If it were mine I might try to keep the chlorine at a very good minimum and change the media in the carbon filter to MTM or some other type of iron removal media. You can remove the chlorine in your drinking water with any carbon based filter at the sink.

Don't get me wrong, I really don't like injecting chlorine into anyone's house if it is possible to do something else, but the carbon can't be lasting long with all the iron it is accumulating.

You will probably still need the equipment with the proposed city water. They never take out hardness and you can be almost assurred there will be chlorine or some other bug killing agent in the water.

bob...

[Mikey]

I don't mind the chlorine. We can't taste it or smell it in the house, and it gives us a good feeling about killing whatever can be killed with chlorine. After a major storm, most municipalities are under a boil-water order for several days, which doesn't affect us. What is a "very good minimum" chlorine level?

I had definitely planned on keeping the equipment after converting to city water -- could probably extend the backwash period for both tanks, since we're starting with (presumably) decent water.

[speedbump]

Where are you in Central Florida?

[Mikey]

Just about midway between Orlando and Tampa -- in the Polk City suburbs. Looks like maybe an hour or so from Riverview.

[speedbump]

Your just a little closer to where all the Hurricanes like to go than I was a few years back.

bob...

[Mikey]

Yeah, we were something like 18mi from the epicenter. It was kind of thrilling seeing 10' waves on our lake which is about 15' deep at its deepest. When I say "central Florida" we're actually about 60 miles from the geographic center of Florida, which bears roughly northwest of us. Oddly enough, the geographic center is closer to the coast than we are, thanks to the panhandle hanging out there. Even more oddly, I just noticed that every Web site which gives both geographic description of the geographic center (12 mi. NNW of Brooksville) and Lat/Lon (28d8.0m N, 81d 37.9m W) have apparently not noticed these two points are about 65 miles apart.

[speedbump]

I'm not too sure, but I think Scary may be a better term for those ten foot waves. I've been in a few of those out in Tampa bay in a 23 foot boat when one of those crazy Bay Pilots was in a hurry to return a large freighter to port.

I'de say where you are and Brooksville are kind of a fur piece apart.

bob...

[Gary Slusser]

It sounds as if you aren't injecting enough chlorine, and/or the solution is too weak. And if the pH is wrong for the use of chlorine, you won't get it working right. And you have to get the pH right before injecting the chlorine.

The retention tank may not be large enough but, does the outlet go out the top, as it has to?

A spin down 'filter' is not a good choice. Disposable cartridges aren't either. You could use Centaur carbon in your filter and replace the filters and retention tank with a special 12" x 60" mixing tank. And it's all within your few hundred dollars range.

[Mikey]

Gary --

What's special about a "mixing" tank? Mine is a 125-gallon tank, and that's our average daily usage, so there's an average 24 hour contact time. It's about 6' tall by 18" in diameter; water enters about 6" from the bottom, exits at the top.

What's special about Centaur carbon? Isn't carbon carbon?

What values do you suggest for pH and residual chlorine? What test kit do you recommend?

I'm off to the QWA Web site for a while, I guess.

[Bob NH]

An 18 inch diameter x 6 ft long tank is about 80 gallons, not counting losses in rounded head or the concave bottom. If someone sold you that as a 125, you were shorted about 45 gallons.

[PEW]

I went that route, gave up on it, and for the last 10 years have used a green sand filter with great success. But, our problem was only iron.

Paul