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Our Excel NE Composting Toilet Installation August 8, 2006

Our family cottage in Ontario was built in the early 1960s. There's a very small bathroom inside which was originally equipped with a potty chair Mum rigged up for us when we were little by adding runners under the seat of an old wooden chair. She removed the seat of the chair and used the runners to hold a porcelain-glazed chamber pot. No more terrifying trips through the woods in the dark to use the outhouse!

A few years later, the potty chair was replaced by a chemical toilet which was vented outdoors via a pipe through bathroom wall. The indoor toilet was used for night-time emergencies only. Every two or three days we'd carry the pail up to the outhouse to empty it.

Now, 40 years later, trips to the outhouse in the night aren't frightening. It's freezing our aging bottoms early in the morning we're trying to avoid. So, an indoor composting toilet is an indulgence whose time has come. No more carrying smelly pails of toilet waste up to the outhouse, and no more frosty bums on those crisp autumn mornings. As well, we know composted toilet waste is much more friendly to the environment than raw toilet waste. Even though the outhouse is about 300 feet from the shoreline, the fact that's it's been there for 45 years gets you thinking that it could be contributing to the nutrient overload in the lake.

We unpack the shipping carton to find that included with the toilet is:

  • the owner's manual and warranty card

  • a 30L (8 gal.) bag of Compost Sure Peat Mix

  • a container of Microbe Mix (dried aerobic microbes to kick start the composting process)

  • a small spray bottle of Compost Quick liquid enzymes to accelerate the composting process and to use as a cleanser on the toilet

  • a length of 1" tubing and a hose clamp for the overflow drain

  • 8 feet of 4" vent pipe to go up through the roof

  • straight fittings to join the pipe sections

  • a diffuser to go on the top of the vent pipe

  • rubber roof flashing to go around the vent pipe

We're off to a great start - the toilet won't fit through the bathroom door! The door is only 24" wide. The Excel NE is 22.5" wide - it fits easily through a standard 30" door, but we need to take our 24" door off the hinges to fit the toilet through. A pretty easy fix, but it would have been nicer to avoid that moment of panic. So, lesson # 1 is don't just measure the room before ordering your toilet, measure the door as well. The toilet comes in one piece and you can't take it apart and reassemble it inside the room.

Because the bathroom is very small, there is only one possible place to fit the toilet. We place the toilet there and use a plumb bob to find the location on the ceiling where we will make the hole for the 4 inch vent pipe.

We make a template of the vent pipe cross-section using 1" styrofoam and use it to mark the outline for the cut on the bathroom ceiling. Then we drill a hole in the ceiling so we can get the keyhole saw in to start cutting. We cut the circle out.

Arghh! There's a rafter directly above the hole! We can't change the location of the toilet as the room is not big enough, so we'll have to cut through the rafter. We push the vent pipe up as high as it can go against the rafter and Don goes into the attic to mark the cut line on the rafter using the edge of the pipe as a guide.

While he's in the attic, he holds a plumb bob against the underside of the roof along the edge of the pipe to be sure it's vertical before marking the 2 spots at the widest point from the rafter. I pull the pipe back down out of the hole and he drills a hole up through the roof on each side of the rafter on the marks he's just made.

The vent pipe will pass through the roof close to the eave, so there's no room in the attic to work. The cutting will all have to be done from outside on the roof.

Composting Toilet Vent Pipe InstallationHere goes! We go up on the roof with a length of vent pipe and a level. I hold the pipe up between the holes Don just drilled and we use the level to check for vertical on 4 sides of the pipe. Then, we mark the outline on the roof with chalk. The outline for the hole is elliptical, not round on the sloped surface of the roof.

Composting Toilet Vent Pipe InstallationWe have no power saw, but we have a generator and an electric drill. We drill numerous holes along the chalk line and use the keyhole saw to finish the cut, but we can't cut through the rafter with it. It's too difficult. So, Don drills a series of holes through the rafter, which works nicely. He smooths the edges of the hole with the keyhole saw.

Composting Toilet Vent Pipe InstallationWe place the pipe lengths on the toilet. Oh no! There is a joint right where it passes through the rafter. This might be awkward, but we're through the roof with a nice snug fit.

Roof Flange For Composting Toilet VentBack up to the roof with a length of pipe and the rubber flange. We lift up the edge of the shingle and remove 3 nails so the flange can slide under and into position with its hole lined up over the hole in the roof. We can't slide the flange up quite far enough, so we cut about 3/4" off the top of the flange. Great! It fits beautifully.

Roof Flange For Composting Toilet VentWe cut the lowest shingle away a bit to fit snugly around the raised portion of the flange. All is lying nice and flat now. We push the pipe through the hole in the flange. A very tight fit. Good! We use some dish soap around the edge of the rubber to make it slipperier so the pipe can go through easier and we can rotate it to fit into that awkward joint just below the roof level. Turns out not to be a problem after all.

Roof Flange For Composting Toilet Vent InstallationMy niece Jennifer is in the bathroom below holding the pipe to keep it from rotating as Don twists the section above the roof to make that joint nice and tight. Done! A nice, tight joint. We can feel the updraft through the vent when we place our hands on the top of the pipe. We put the diffuser on and we're done. We decide to keep the extra section of pipe we bought but didn't use.
Completed Composting Toilet Vent InstallationThe vent is on the east side of the peak, with prevailing westerly winds. Including the diffuser, the top of the vent is about 1 foot below the level of the peak. We may want to add some length to the vent to bring it up above the peak level. We'll try it out first and see. It might look a bit weird if it was that high.
Composting Toilet Overflow Drain Installation Now to hook up the overflow drain. The 1" PVC tubing and hose clamp that are included with the toilet do not allow us to have the drain exit the building through the floor, as the PVC crimps when we try to bend it that sharply, so we need to go to the hardware store for 2 elbows and 3 hose clamps.
We know there won't be much liquid, if any, draining through the overflow drain, as most often there will be only two or three people using the toilet. We drill a 1" hole through the floor beside the wall and run the hose into a perforated coffee can buried in the sand under the cottage.

All that's left now is to glue all the joints and brace the rafter we had to cut through. Don will cut pieces of 2 x 4 to flank the vent pipe and secure them to the existing rafter with carriage bolts.

Composting Toilet Installation CompleteWe spray the inside of the drum with the enzyme spray, add bulking mixture and water according to the directions, add microbe mix powdered enzymes to get everything off to a good start, and the toilet is ready for use.

July 2007 Update:

Don reports that there is some downdraft affecting the venting of the toilet and creating an odor in the bathroom. We knew that was a possibility when we left the top of the vent pipe below the level of the roof peak. He added a length of pipe so that the vent pipe is now taller than the peak of the roof, and he also cut away some branches of the white pine which were overhanging the vent pipe. He also discovered that the downdraft issue is complicated by the chimney of the wood stove, which is a larger diameter pipe than the toilet vent so that air is drawn down the toilet vent and up the stove pipe. Keeping the bathroom door closed helps to control the air flow problem but makes the bathroom cold.

Now that cottage season is over for the year, Don reports that the toilet has worked well. There was one long weekend over the summer when there were 5 adults (the maximum capacity for the Excel NE) at the cottage and by the end of the weekend they were noticing a slight urine smell. Other than that, he has had no problems.

October 2009 Update:

In July of 2009, a storm passed through the area with very high winds, taking down some trees and unfortunately, the toilet vent stack as well. Don decided to put a 12 Volt fan in the stack instead of running it up so high again and risking further wind damage. This has completely eliminated all the downdraft problems, and they are pleased to find that the fan runs quietly enough that they are not bothered by it at all.

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