"Toilet bowl love"

The prison equivalent of phone sex makes use of the pipes of the plumbing system, as explained at Truthdig:

Life behind bars in Union County jail and some other American penal institutions revolves around an improvised system of cell-to-cell communication through the plumbing. Known as the “bowl phone,” it crudely replicates the speaking tubes in ships that sailors once shouted through. Drained metal toilets are used as megaphones to build friendships, carry out courtship, fall in love—although the lovers may never meet—have
phone sex, pray and carry out religious conversion, pass news about court cases and families and exchange gossip...

“You take a piece of cloth,” says Blount, a small, wispy African-American in her 40s. “You take the water out [of the bowl]. You keep pumpin’ the water out until it get lower. Then you take the little cup or somethin’. You take a little sock or a little cloth or somethin’. You pump it out with the cloth, the water out. And as you’re doin’ that it’s the water’s going out. It’s goin’, it’s goin’. It don’t take but like about a minute.”...

To send or receive a call, a male prisoner one or two floors below must similarly prepare a bowl phone. It is difficult for the parties to hear each other if they are separated by more than two floors. To keep the lines of communication open, bowl phones are seldom used as toilets and rarely are flushed. Cells designated by prisoners become, in essence, public phone booths, known by their cell numbers...

I ask what most of the prisoners like to talk about. “Sex,” Pabey and Blount answer at once. 

More at the link, if you really need to know...

Illustration by Mr. Fish.