Monday, October 31, 2005

House Project: Getting the Lead Out

I have mentioned previously that there's a worrisome amount of lead in our well water--one test showed 15 micrograms per liter (the EPA action level for lead), a later test showed 31 micrograms per liter. I have also mentioned that whole house lead filters seemed not to exist, because lead problems are in the house pipes--there was no point in filtering lead out before the pipes.

Anyway, my builder was golfing with a guy who sells Harmsco's whole house filter housings, and there is a lead filter available for it from KX Industries that claims to meet ANSI Standard 53 for lead removal. The testing procedure apparently involves 210 micrograms/liter of lead reduced below the 15 micrograms/liter EPA action level. I'm not expecting it to take 31 micrograms/liter (my most recent test) down to 0, but if I get down to 12 micrograms/liter, I guess that I will be happy.

The sales material indicates that each filter should last 2500 gallons at 0.75 gallons per minute, and the filters sell for about $7 each. The housing that I ordered takes 14 filters, so a complete set should filter about 35,000 gallons.

I am not expecting to use more than three gallons per minute except on very rare occasions: showering, dishwasher, and washing machine all going at once, for example. At three gallons per minute, each filter will flow about .21 gallons per minute.

I'm told that the lower rate of flow, the longer the filters will last, and the more effective they are at removing lead. This is not too startling; the more time that the water is in contact with the filter, the more chance the filter has to react to the lead. We are also going to keep the particulate filter already in the line upstream of this; the more of the large particles (25 microns and larger) that we keep from reaching this filter, the longer it will last.

Of course, most of the high consumption uses in a house are situations where a little more lead in the water isn't a big deal. If the lead level in the washing machine is 15 micrograms/liter instead of 10, I'm not much worried, and ditto for the shower. Very little of this lead will end up in your body. The dishwasher is another matter; you don't want lead on your plates or utensils. I suppose that we can improve the situation by trying not to run the dishwasher while we are drawing a lot of other water.

Anyway, after installation, I'll run another lead test, and then against after three months and six months in the house, to see how rapidly the filters are degrading.

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