Sewer line plugging / design??

[Anonymous]

My sewer design calls for a 30-ft long 4-inch line running from my house (line begins 18-inches deep) to my tank (inlet is 30 inches deep). The sewer line is to slope 2 inches per foot. The winters are cold (-10 to +10 F at night is typical), and the inlet water is also cold (40 F). The toilet (one only; one bedroom, ground floor) will be the only feed to the sewer line. 1) Will the steep line slope and its long length likely result in solids accumulating in the line? 2) What type of toilet should I select to minimize the chances of plugging? (Water is cheap.)

[SylvanLMPParticipant]

If your starting your sewer @ 18″ below grade and ending up 30″ below grade and having a developed length of only 30′ YOU had better recheck your statement of 2″ per FT

Figuring even a pitch of 4% (1/2″ per ft) over FT 30 your total drop would be 15″ BUT your actual drop is only 12″ so your actual pitch is just hovering around 3/8″ (3%) pitch per ft which would bring you in around 11.25.”

Now about the frost line In NYC which has a higher temperature than -10 degrees our frost level is around 4 ft deep

I wouldn’t worry about water to waste as you said this is not an issue BUT I would be more concerned about the ambient temperature surrounding your soil piping.

Why not use a 1.6 GPF and use a good quality heat tape to protect this pipe from freezing. If for example left this piping unused all night long THEN used a toilet/sink chances are the water would freeze long before reaching the discharge point.

You could insulate this piping with a heavy fiberglass and then a felt covering for moisture protection with heat tape applied under the insulation.

Good luck

[Art_xyzParticipant]

As a practical matter, I don’t believe the slope or type of toilet will matter.

[John Aldrich1Participant]

Paul, I agree with art! The temperature of the soil around the pipe will never be -10 F. at your cabin. The use of insulation and a heat tape are not necessary for this installation, or I would have specified them. JWA

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