No need to worry about discovery of attic-dwelling mud wasps

Q: I have probably 20 tan-colored things way up in the rafters inside my attic. Could these be termites? None are attached to each other and they are at random places. The house is 26 years old and has roof trusses and a composite roof.

A: Mud-dauber nests are what you are seeing up there. "Mud wasp" is another term for these harmless critters. The female captures several spiders as provisions and paralyzes them with a nasty sting. She lays an egg on the spider, the larva hatches, and proceeds to feast on freeze-dried spider. Several of these spider and larva mixes are heaped by the mother wasp into a tubular mudball.

These wasps do not sting humans, unless you are ugly enough to be mistaken for a spider, and they do not harm the building in any way. No pest control is needed. If you want to grab one off the rafter, feel free. Crack it open and you can see the spiders, or spider leftovers, and larva or empty casing. Very interesting bits of entomology!

Q: I have a 3-year-old condo. The heating system is actually nothing more than my gas-powered water heater, connected via water tubes to four different wall units with blower fans. It works great in the winter and I am basically happy with it, but now that the weather is warmer, a small amount of heat is always coming out of each heating unit, even with the thermostats and fans fully off. Turning the water temperature down on the tank helped a bit, but mainly served to give me a lukewarm shower. Help!

A: Since you have a shared domestic hot-water tank and heating system, the circulating pump for the heating portion is probably running continually, or at least more than you would like. You are feeling the hot water running through the radiators (encased partially in the wall). You have a timer that controls the heating system's circulating pump, located near the tank.

During warmer months the pump should come on only once per day, to circulate water through the system for fifteen minutes (or the smallest amount of time the timer will allow you). The pump should also come on when the thermostat calls for heat, and go right off again. Pump operation likely cannot be heard, but can be felt by placing your hand over it and feeling for the vibration. Test for correct timer/pump/thermostat operation this way. Adjust the timer to run only once, preferably just before you get up in the morning.

Secondly, you will have a domestic water temperature-mixing valve that allows the tank temperature to be turned up or down according to demand on the heaters without scalding you. In the summer you can turn the temperature down at the tank and up at the mixing valve to save energy. During the cold months, go up with the tank temperature and down at the mixing valve. Turning up the temperature in the winter helps you heat the house, take a shower, and do a load of dishes at the same time. Having the pump come on right before you wake up preheats the lines, adding additional heating capacity to the system when you need it most on cold mornings.

Q: We've just moved in a house in Redmond built in 1972. The living-room fireplace has a wood mantle with brick showing around the opening. There is soft white powdery stuff growing on the bricks. It falls off to the floor every day. It feels like talcum powder. I think it's coming from up above, behind the facade. What do we do?.

A: Efflorescence is the salty debris left behind as saturated masonry-containing products dry. The presence of efflorescence means you have wet brick, and in your case, likely a flashing leak, or a damaged chimney cap. You need to determine where the leak is originating and repair it. Removal of efflorescence can be accomplished with muriatic acid diluted with water, and a stiff brush. Muriatic acid can be found at home improvement stores and some pool supply stores. As when handling any hazardous chemical, follow all directions carefully.

Q: When you turn on the gas burner on the stove and occasionally see little sparks or changes in color, what is the explanation? I think it's ants. They get in the line and explode as they come to the surface. But I am open to other explanations.

A: You're close. Unfortunately, they are actually fugitive baby spiders, running from hungry mud-wasp larva. Or it could mean the burner on your stove is dirty, or worn, and needs cleaning. Take your pick. It's not burning the gas completely. After the lady above is through with her stiff brush, ask if you can borrow it.

Darrell Hay answers reader questions. Call 206-464-8514, e-mail dhay@seattletimes.com. Sorry, no personal replies. More columns at www.seattletimes.com/columnists.