We all know Black Friday as the post-Thanksgiving frenzy of holiday shoppers chasing the best doorbuster deals, but plumbers at Roto-Rooters have a slightly grosser term for their busiest day of the year.

“Brown Friday” — named after the dirty water and sewage that plumbing and drain specialists are asked to deal with — requires virtually all 7,000 Roto-Rooter service technicians across the country to call on the households that overloaded garbage disposals with turkey bits and clogged toilets from frequent flushing.

The company’s incoming calls for service typically spike by 50 percent over the Friday average, and record a 27 percent uptick in business over any other Friday through Sunday period in November.

“We’re slammed,” said company spokesman Paul Abrams. “It’s all hands on deck.”

The main culprit?

Potato peels, turkey skins and grease that block kitchen sinks and break down disposals from Thanksgiving meal prep or a relative’s attempt to clean up.

Starchy foods, in particular, like rice and pasta can cause trouble because they swell up. Turkey drippings also “solidify like candle wax and narrow the diameter of your drain pipe,” Abrams said. “Almost every piece of the meal itself is an ideal food for clogging drains.”

Almost as frequent as requests to clear obstructed kitchen sinks are frantic calls to fix clogged sewers and toilets. Holiday guests put an additional strain on residential drain systems, which are susceptible to blockages from the higher volume of water.

“Suddenly, you’ve got extra showers, extra toilet flushes and even maybe even extra loads of laundry,” Abrams said. “All that extra water goes into the same sewer pipe as before, but a clog that was hardly noticeable because the drains were a little slow is suddenly causing a backup.”

Enlightened homeowners typically call on the Monday before Thanksgiving to have professionals take a look at slow-moving drains before their house turns into a family zoo. Those who wait until there’s a clog might try using a plunger or Drano, Abrams said. When that doesn’t work, the panic sets in.

Abrams thinks people force themselves to wait until Friday to make that call for help because they expect to pay an outrageous fee for a service call on nights and holidays. Most Roto-Rooter locations charge the standard rate, even on Thanksgiving.

So don’t let Uncle Joe scrape his heaping plate of turkey bones into the disposal.

And place a plunger in the bathroom, Abrams suggested. “No one wants to make that walk of shame to the host,” he said.

Baby your pipes

To avoid a visit from the plumber over the holidays, follow these tips:

• Don’t pour fats or cooking oils down the drain. They will solidify in pipes and choke drains.

• Never put stringy, fibrous or starchy waste down the garbage disposal. Disposals can handle most scraps in small quantities, but it’s best to toss food waste into the trash or compost.

• Make sure the disposal is running when you feed it food scraps.

• Don’t flush cotton balls or wet wipes down toilets. They don’t dissolve and will cause clogs. Put a wastebasket in the bathroom so guests won’t flush these items.