Drain traps play critical role

Q: Our senior community newspaper said to “make sure you run at least a quart of water in all the seldom-used sink or tub drains in the house every few weeks, as they can dry out and allow sewer gas to enter the house.” That sent me flying into my guest bathroom — and removing boxes I had stored behind shower curtain in a never-used tub — and running some water.

But I later realized I do use that toilet and sink frequently, and wondered if that was sufficient. I know a sink has the U-trap for that reason. Does a tub have one, or is the whole system connected? Please enlighten an ignorant widow. — Janet C., Toms River, N.J.

A: Each drain fixture in a home will have a trap or bend of some type to prevent backups, so you do need to run water through each unused drain.

You brought up a very good point about system maintenance. Drain traps (the “U” or “S” bends visible beneath toilets and sinks) prevent the liquids, solids and gases that are moving through the bigger drain lines from exiting the system at the wrong point — namely the sink, toilet or tub. The water that remains in a drain trap after the faucet is turned off creates an additional pressure seal against exiting gases.

If the water evaporates from the trap due to non-use, there’s a risk of sewer gas entering the home, especially on lower levels like the basement. Sewer gas is methane gas, and in addition to its explosive qualities, it can cause headaches, insomnia, irritability and blurred vision.

Stale water in drain traps can also attract fruit flies, which lay their eggs in the water and can generate a foul smell. It’s another reason to run water through the drain every two weeks (plus a cup of white vinegar to retard bacteria, mold and pests).

HOME TIP: Run at least a quart of water through unused drains every two weeks to prevent sewer gas from entering the home and keep the drains fresh.