The case of the black scum: how to solve it in jetted tubs

Q: We have a jetted bathtub in the master bathroom. We rarely use it, which I think might be contributing to the following problem: When my wife cleaned it the other day, she ran the jets to see whether they still worked, and a bunch of black stuff came out of every one. It was nasty! After draining the tub, this stuff stuck to the sides of the tub and wouldn't wash away. It was so gross, she doesn't want to go into the bathroom again, much less ever take a bath again, jets or no. Does the whole system need to be taken apart and disassembled? How can I clean this and keep it from happening again?

A: If installed correctly, a jetted tub should drain almost all water inside the system when the tub is emptied. But there always will be at least some trapped moisture, warm temperatures and a dark environment for who-knows-what to grow. Soap scum, oils, skin cells and whatever else washes off in the bath also ends up coating the pipes, creating this black goo. Deteriorated rubber from the pipe gaskets also can be found in the water. Black algae can smell, too.

The creeping crud can be kept to a visual minimum by running the motor (when the tub is full of water) regularly. Putting bleach into the tub and running the jets will kill bacteria, but it won't dissolve the scum. Dishwashing detergent will help with dislodging some of the nastiness, and you will be hard-pressed to find a more efficient bubble-maker. I tried this recently and haven't seen such an impressive stack of bubbles running out into the street since I was a teenager — when we dropped a box of Tide into a fountain. Accidentally, of course.

Dwight Pauls with Classic Pool and Spa in Auburn says there are chemical treatments available from pool and spa dealers, and for less than $20. Many of his customers have had good luck with Swirl-Away, both for black algae and cobalt staining. (Cobalt staining is the topical mark in fiberglass tubs where a small hole in the acrylic top coating allows water to react with the fiberglass base beneath. Bleach won't remove this, either.)

While dealing with the jetted tub, this is a good time to check the ground fault circuit interrupter (GFCI). No matter the age of the wiring in the house, a jetted tub should have a GFCI connected to the circuit used by the motor. An electrical shock in a bathtub can be fatal. The GFCI device may be located in the bathroom, an adjoining closet or wall, the main electrical panel or at the outlet the motor is connected to. Run the motor, trip the GFCI and hear the motor stop. This is the only sure way to test it.

To avoid spraying yourself with water, fill the tub over the top of the highest jet and, obviously, don't run the motor dry. All motors and components should be physically accessible from a removable front panel, the exterior of the building or below or from the side in a vanity cabinet. Many are not accessible, having been tiled-over, or the access simply forgotten. When it comes time to replace a leaking motor or pipe, cutting into the wall tile in a hurry can be a hassle.

Q: Suggestions on whether to use blown-in insulation, fiberglass or foam sheets for our uninsulated cathedral ceiling? A new 30-year composition roof (3:12 pitch) with full ridge vent is going onto our 50-year-old house.

A: Rafter size and the desired amount of insulation are the deciding factors. Blown-in is cheapest but not a good choice for a sloped ceiling. Blown-in sloughs out of position on sloped ceilings, blocking the lower vents and leaving the top uninsulated. A separate vapor barrier is needed, also.

Foam costs the most and will be the best choice if you desire high R-values and/or have narrow cord rafters, but it may not be necessary to achieve today's standard of R-38 if you have 2x12 rafters — but that is doubtful in a '50's era house.

Fiberglass comes with an integral kraft paper vapor barrier, or encapsulated in plastic. Be sure to turn the vapor barrier toward the living space, do not squish it down and leave room for air transfer along the top. Two-by-six rafters are typical in that era, and fiberglass provides R-19.

Darrell Hay answers readers' questions. Call 206-464-8514 to record your question, or e-mail dhay@seattletimes.com. Sorry, no personal replies. More columns at www.seattletimes.com/columnists.