The sulfur-and-mildew smell in a San Mateo house that was not coming from the water heater

Two years of blaming the well

The house sits on US 17 in San Mateo, a 1970s ranch on a sandy lot with a private well like most of the county outside the city water system. The water has the iron and sulfur the Floridan Aquifer hands out across rural Putnam. For two years the owner noticed a rotten-egg-and-mildew smell at the supply registers for the first minute after the air conditioner started, and assumed it was the water heater, which was the only thing in the house that smelled the same.

The water heater was fine. The smell came from a drain pan under the indoor coil, scaled orange with iron, holding a half inch of stagnant water that never drained, and from a return plenum with a gap that was pulling air from a crawlspace where the duct sweated all summer. Hydrogen sulfide from the showers found its way to the return too. Three sources, one smell, and not a thing a filter would have fixed.

What Cook’s checks on an indoor air call

Indoor air problems in this county come from the house as much as the equipment, so the inspection covers both:

1. Readings first. Humidity room by room, particulate levels, static pressure across the duct, and the temperature drop across the coil.
2. The wet places. Indoor coil, drain pan, drain line, and the condensate trap. On well water, we look for scale and stagnant water specifically.
3. The return side. Where the returns pull from, whether the plenum is sealed, and whether a crawlspace, attic or garage is being drawn into the house.
4. The duct and its surroundings. Belly duct under manufactured homes in East Palatka and the rural ZIPs, soffit duct in historic-district retrofits, and whether any of it is sweating, split or lying in standing water.
5. The filter situation. Size, type, how it seats, and whether air is bypassing around it.
6. The water. Not a plumbing inspection, but a question about the well, the softener or aerator if there is one, and the smell at the hot taps.
7. The history. Flooding from the St. Johns, Dunns Creek or Crescent Lake, renovations, new pets, a change in who lives in the house.

The Putnam County pattern

After enough of these visits across Putnam County, the causes cluster:

The fix for most of those is cheaper than the gadget the homeowner was about to buy. Seal the returns, clean and treat the pan, correct the filter, and the air changes. Then, if the readings still say so, add equipment.

Call 866-266-5709

Why two air-quality quotes can differ so much

Cook’s quotes indoor air work after the inspection, and the drivers are predictable:

• Sealing and repair of returns and duct is the least expensive and most effective step, and where most visits start.
• A media filter cabinet is a modest add-on with a large effect on dust and pollen.
• A UV light at the coil is a small install that stops the coil and pan from growing what causes the smell.
• A whole-home dehumidifier is a larger investment and the right one for damp houses the air conditioner cannot dry, including lake cottages and older homes with high ceilings.
• Whole-home purification and ventilation systems from the Lennox Healthy Climate line sit at the top, and suit tight new builds and households with asthma.
• Access matters: a crawlspace in sand under a double-wide is faster to work in than an attic retrofit in a two-story Hammock house.

Prices are quoted before anything is installed, and a wrong product is never the plan. Financing is available on larger whole-home systems; the terms are discussed in person.

When replacing the equipment is the real answer

Sometimes the inspection ends somewhere the homeowner did not expect. An air conditioner that is a size too large for the house, common in Palatka, will never run long enough to dehumidify, and a dehumidifier bolted onto it is treating the symptom. A fifteen-year-old air handler with a rusted pan, a corroded coil and a blower that cannot handle a better filter is not worth adding accessories to. And a duct system that has sweated and sagged under a manufactured home for twenty years is replaced, not cleaned.

In those cases we say so, quote the replacement as its own free estimate, and size the new equipment to the house so the humidity problem goes away with the old unit. For the San Mateo ranch, the answer was smaller: a new pan and drain with treatment for the well water, the return plenum sealed, a UV lamp mounted over the coil, and a conversation about treating the water at the house. The smell was gone the first week.

Call 866-266-5709 to start with the readings.