Q: I have a 20-year-old softener on a shallow 50 foot well. It has worked good over this period but the iron removal has never been good. The latest raw water chemical analysis shows a pH of 6.9, hardness of 6.0 and iron of 2 ppm.

I keep the prefilter screen in the head cleaned and have changed the timer head several times over the 20 years. I have iron buildup in the toilet tanks and have to clean with "Iron Out" and purge the water heater and the pressure tanks every six months.

The water tastes very good, although we go through seasonal turbidity problems triggered by the weather. We do have spotting of the shower stall, toilet bowls, the Jacuzzi and dishwasher, but they clean with "Iron Out." This takes out the iron bacteria but not the ring stains in the toilet bowls.

A sales rep recommended two double tanks, one active and one regenerating. The top tank has 0.2 cu. ft. of ceramic Macrolite and the bottom tank has 0.7 cu. ft. of standard resin. This costs $4,000, which is way over my budget.

Why can't I add a stand-alone ceramic backwashing unit ahead of the softener? I prefer to add another regenerating filter instead of a cartridge for the turbidity.

Do you have any advice on how I can improve this system to remove iron?

— Enumclaw, Washington

A: From your description I'm thinking that you have a water softener, which is intended to remove the iron and the hardness. The pH is neutral so that is no issue. So far, it would be expected that a single softener would easily solve your problem. This is clearly not happening.

However, from your other comments I think it's possible that you may have some combined tannin and iron because you are unable to clean all the stains with Iron Out and because you have a shallow well, which would be more subject to tannin intrusion. A standard softening resin cannot remove iron bacteria or a tannin-iron combination. You believe you also have iron bacteria but you don't discuss this much.

I recommend that you determine if you have tannins and/or iron bacteria. Iron bacteria are frequently identified by the presence of slime in the toilet tank. Tannins can be tested by a field test kit. If you have tannins or iron bacteria you will need different treatment. Find a reputable dealer for advice on this. The bacteria often require chlorination and the tannins require a different ion exchange resin.

Your other comments regarding excessive cleaning are not consistent with a softener that is in good operating condition. The iron and hardness levels are not that high. I'm disappointed to hear that you have had to change the control valve "several" times in 20 years.

Barring the presence of tannins or iron bacteria you seem to need a filter for the occasional turbidity followed by a softener. There are several media that can filter turbidity … most single media like Filter-Ag can filter down to 20-40 microns. Multimedia filters filter down to about 15-20 microns. The ceramic that has been proposed to you advertises that it filters down to 5 microns. It also can filter at higher flow rates and backwash at lesser flow rates.

This is probably why it can be placed in a small tank above a softener tank (the softener valve is suitable for the lower backwash rates of both the ceramic and the softening resin). This medium is also capable of greater sediment-loading before requiring backwashing. I don't, however, know why two double-tanks like this are being proposed unless it is to regenerate with treated water.

If you filter turbidity or sediment in a separate tank it should precede the softener. This will require two control valves. The proposed double tank uses only one valve, unless you have two doubles (two valves).

Q: I see the words "working pressure" and "burst pressure" on the specifications sheets of fiberglass tanks. I don't understand what these two designations mean.

A: In most cases, "working pressure" refers to the pressure that randomly-selected-production components are subjected to, in order to assure proper quality control. On a less frequent basis tanks are placed in a room built to withstand the explosion or bursting of a tank due to increasingly higher internal pressure … "burst pressure."

There is a specific test procedure that must be met by WQA standards in order for a tank to receive certification.

So, every tank should be able to withstand the working pressure on a continuous basis. This must be adhered to. The burst pressure is just for background information.

Q: One of our local manufacturers recently asked us if we could quote on a dealkalizer. We don't know what this is but would like to be prepared in case it comes up again. We are in a city with many large manufacturers. Can you explain dealkalizers to us?

A: Dealkalizers are ion exchangers, like softeners, but they primarily remove sulfate (SO₄^-) and bicarbonate (HCO₃^-). They contain anion resin and need to be preceded by a softener to prevent hardness fouling.

Dealkalizers are very simple to operate because they regenerate with sodium chloride, although better performance is achieved when a small amount of sodium hydroxide (NaOH^-) is added to the salt. They are extremely useful as pretreatment for feedwater of medium temperature and medium pressure boilers.

There are three forms of alkalinity: Bicarbonate (HCO₃^-), carbonate (CO₃^-), and hydroxide (OH^-). A dealkalizer's benefit is that, by reducing bicarbonate, it reduces the formation of carbonic acid (H₂CO₃^--). This is especially important in the condensate return lines from the boiler.

Carbonate does not exist in neutral pH water but boiler feedwater is often fed with OH^- after dealkalization, thereby raising the pH. This raises pH where carbonate, and subsequently carbonic acid, will be formed if bicarbonate is not reduced or eliminated. A dealkalizer is not intended to remove hydroxide alkalinity, nor would it be useful.

Reducing bicarbonate, carbonate and hence carbonic acid, which is corrosive to condensate return lines, reduces expensive boiler failure.

For the typical 24-hour operating plant both the softeners and the dealkalizers should be alternating twins or duplexes.

You will require some sizing and design-engineering assistance to be a vendor and service source of dealkalizers. You will also need engineering assistance in the start-up of your first system.

David M. Bauman, CWS-VI, CI, CCO, is technical editor of Water Technology^® and a water treatment consultant in Manitowoc, Wis. He received his B.A. from the University of Illinois in Industrial Design. He can be reached by email at: dp-bauman@sbcglobal.net.

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