Came back to a musty house: what a summer closed up does

The West Valley empties out in summer. Surprise, Sun City, Sun City West, Sun City Grand, and the surrounding communities have a large seasonal population, and a great many houses here sit closed from May to October with nobody in them.

That produces a specific and very predictable set of October phone calls.

The three things that go wrong

1. The AC was off, or set too high. An air conditioner is also a dehumidifier. A closed house through a Phoenix monsoon, with outdoor dew points climbing into the high 50s and 60s from July into September, and no cooling running at all, can reach interior humidity that supports growth on surfaces: closet walls, the backs of furniture, leather, and drywall in still corners.

This is the version that surprises people most, because “it is dry in Arizona” is true for most of the year and not true for the weeks that matter.

2. The condensate line clogged. The most common single cause. The air handler produces water all summer, it drains through a condensate line, and when that line clogs the pan overflows onto drywall in an enclosed closet. With somebody in the house you notice the smell or the water within days. With nobody there, it runs for weeks. See mold in the AC closet.

3. Something leaked. A supply line, a water heater, a toilet valve, an appliance hose. A leak that would be a mop and a plumber if you were home becomes a months-long soak if you are not. This is the expensive version, and it is the one a water shut-off prevents entirely.

What to do the day you get back

Before you unpack.

1. Walk the house and smell each room, scoring the musty smell. Strongest room is the starting point.
2. Open the AC closet. Look in the drain pan, at the floor, and at the bottom few inches of drywall. This is where it usually is.
3. Check the water meter. Shut everything off, read it, wait an hour, read again. Movement means something is leaking right now.
4. Walk the floors barefoot. A warm patch on a slab is a hot-water slab leak.
5. Open every cabinet and smell inside, especially under sinks.
6. Look at the ceilings, particularly under any flat roof section or near penetrations, for staining from a monsoon leak.
7. Run water in every rarely used sink, shower, and floor drain. Dry P-traps let sewer gas in and it is mistaken for mould constantly in houses that have sat empty.
8. Check the attic if there is any ceiling staining.

Take photographs of anything you find, with the date, before touching it.

Which one is it?

What it costs

The visual assessment is free, and a good share of these end there with “flush the condensate line and clean this up.”

Published on the pricing page, and the remediation calculator prices a scope.

The setup that prevents all of it

Four things, and the first one is the important one.

1. Shut the water off at the main. This single action eliminates the expensive version of this problem entirely. No supply line, water heater, toilet valve, or appliance hose can flood a house that has no water in its pipes. If you do nothing else, do this.

2. Flush the condensate line before you go. Ten minutes with a wet vac at the outlet. Then make sure the float switch on the secondary pan is present and connected, because that switch is the last line of defence and it is regularly bypassed by somebody who got tired of the system shutting off.

3. Leave the AC running at a setback, not off. An air conditioner removes humidity as well as heat, and a closed house through monsoon with nothing running is the condition that produces the whole-house musty smell.

4. Have somebody check it monthly. A neighbour, a family member, or a service. Ten minutes: look at the AC closet, look at the ceilings, look under the sinks, smell each room. That is how a six-week problem stays a six-week problem instead of a five-month one.

A smart water shut-off with leak detection is worth considering if the house sits empty for months every year. So is a leak sensor in the AC closet, which is inexpensive and sits exactly where the water appears.

No state licence for mold work

The state of Arizona has no licence for mold remediation, so an ad promising a licensed mold remediator is promising something that does not exist. Before work begins, ask for IICRC certification, containment and negative air, independent clearance testing, and the scope in writing. Ask those questions of us too, and distrust anyone claiming a licence Arizona does not issue.

What to expect on the call

How long the house was closed, whether the AC was running and at what setting, what you found on the walk-through, whether the meter moves, and whether anything is visibly wet. The assessment is free and October is the busiest month, so booking as soon as you are back is worth doing. We cover Surprise, Sun City West, Sun City, Waddell, Litchfield Park, Goodyear, and Buckeye.