How To Install Flush Toilets In A Home With Above-The-Floor Plumbing

Here at the Border Fort in southern Cochise County, Arizona, we've done without flush toilets for the past two and a half years. Oh, we'd figured out how to install them, even with our home sitting flat on the Earth and the drainpipe running above the floor all the way through the house.

What we did not know was how to pay for them.

Now, however, with finances squared away once again, it was time to get those porcelain potties up and running...so to speak.

Obviously, the primary problem revolved around the fact that sewage doesn't run uphill unless it's being pumped. I talked with a fellow in Home Depot who knows a lot and thinks he knows everything. He informed me I was up S**t Creek without a paddle, mostly because I refused to pierce the roof to vent the sewage pipe--and without that, a 90 degree elbow right below the toilet would lead to major clogging problems.

And if I used a couple of 45 degree elbows to get a longer "sweep", the "box floor" would have to be so high, I'd hit my head on the ceiling and/or Pam would sooner or later take a nasty fall off that super-high step-up. Which, with her osteoporosis and various other ailments, was not an attractive prospect.

Okay, so I thought about that. They have such things as "grinder toilets", macerating units that (get this) chop up your poo with an electrically powered motor as it exits the toilet. Such units are often "rear exit" (pun probably unintended), meaning I could likely set a couple of those up atop 3 1/2" high floors and be done with it.

Lots of problems with that setup, though. Costly, for one thing. The power requirements, for another. But most of all: Gross! A s**t chopper?

No way.

So...Mr. Knows Less Than He Thinks had denied the likelihood of the existence of workable indoor negative-pressure-activated vents. These are called air activated vents, or AAV units. I have a small one (purchased from Home Depot, no less) installed to vent the utility sink drain.

Works like a charm. But Mr. KLTHT snorted in derision at the very idea of such a thing being available to vent big three inch (or larger) toilet lines, keeping sewer gases from excaping and such like that. Doncha know.

Turned out he didn't know. Oatey makes them, large and small. Bought one from Amazon, $29 including the shipping. Certified for 3" piping with no sewer gas escaping for a minimum of 500,000 flushes.

Now it was time to put together a bit of piping, run from the sewer pipe stub on into the bathrooms, and then get to building a box floor.

Running the 3" pipe was a bit tricky. Standard plumbing manuals tell us to use a 1/8" drop for every 12 feet of run. I'm guessing that's so you can install a long length of pipe and not end up having to sit on the roof to take a dump, keeping it so close to level, but that's only 1/96" of drop per foot. Or in other words, roughly a 1% grade.

Frankly, I don't trust that a whole lot, especially with the latter day low-volume flush toilets. Back in the day, we used 5 gallons per flush. Now it's down to 1.28 gallons.

Scary.

So my drainpipes always drop at least 1/4 inch per twelve feet, minimum.

Now, wangling that through the places it had to go and into the bathrooms--lots and lots of double, triple, and quadruple checking with the level, you betcha.

Additiionally, one Y was installed along the way, taking it down to a 2" line on the "branch off". That 2" branch is capped for now. Later, whenever I can get around to tackling the installation of showers and bathroom sinks, that Y will be the point where gray water hits the main sewer line--about 3 feet from my toilet and 4 feet from Pam's.

The AAV (air admittance valve) is just eight inches ahead of that in the main line. Which means that if our toilets can flush their contents four feet down the line, extra water from the showers and sinks will make sure the "heavier stuff" makes it the rest of the way down the line to the septic tank.

With the toilet drain lines installed (and a couple of gallons of water poured down them to make sure they flow in the right direction), it's time to build the 2"x4" box floor.

By a stroke of good fortune, it turned out that three so-called 2"x4" boards on edge plus one layer of flat 2"x4" boards plus a top flooring layer of 15/32" OSB strand board worked out just right to seat the toilet mounting flange.

But let's start with the 2"x4" box floor framing as shown in the photos.

The trickiest part of the piping run is right where the main sewer line brings effluent from Pam's bathroom through our mutual wall (the home is built with mirror image bathrooms, one for each bedroom) into my bathroom. From there, it joins with the outlet from my toilet and then flows on out through the "north wall" to eventually make its way to the septic tank.

Additionally, the 2" pipe planned for carrying gray water waste from showers and sinks must also run a parallel route--and be stubbed off with some degree of availability for whenever I can get around to installing the rest of the plumbing.

Yes, that sounds confusing. Picture time.

With "enough" of the gray water (2") line in place for later use, that aspect of the piping can be "boarded over" and ignored until its needed. Had that not been done, it would have been pretty much impossible to lay the pipe after topping off the floor (unless the floor was torn up again).

So: Time to cut the "toilet holes", cutting pieces of OSB strand board to size (1 per bathroom). Access cutouts will also be added so that the remaining piping work can be accomplished without too much cursing.

The boards fit beautifully in both bathrooms--measure twice (or several times, actually), cut once, done!

Whew!

My age started showing when it came time to add the toilet tank to the bowl. The last toilet I installed was so long ago that "toilet and bowl" was a one-piece unit. Mounting the tank atop a rubber gasket and cinching it down with a couple of bolts was an entirely new experience.

So was the absolute need to make sure the tank rested against something. The most common something is a wall, a fact which is reflected by the tank lid design: It's flat in the back, does not jut to the rear of the tank at all.

We saw what happens if you don't brace the tank when we rented a house for Pam's son and his family. In one of the bathrooms, the tank rests against the wall, all right--but it has to lean back at a significant angle to get there. How that flexible rubber seal has kept from leaking this long, who knows?

Fortunately, I can cheat. There's nobody (except my wife) to tell me I'm doing it wrong, so a couple of chunks of 2" x 4" lumber attached to the wall provide a "backrest" for the tank.

Note: It's not required, but having a qualified IC (Inspector Cat) on hand to check out your work is definitely advantageous.

Today was (hopefully) the big day. The only work remaining before test-flushing the two toilets involved (a) adding the two step boards in Pam's bathroom and (b) running the 1/2" supply water line to both thrones.

Naturally, that was easier said than done. Turned out I'd only stocked up on four (!) 90 degree elbows when twenty or more were likely to be needed.

Back to Home Depot. What the hey; it's only a thirty mile round trip.

The half-inch line is thankfully much easier to handle than the big drain lines. PVC pipe of such minimal diameter is nearly as flexible as your favorite pole dancer, and that's a good thing. Missed the matchup connection by a few inches? No big; bend the pipe and be done with it.

For connecting the PVC to the toilet tank, a flexible metal hose is used--standard, and available at any home improvement and/or hardware store. But there is something important here: The ACE Hardware brand turned out to be vastly superior to the design found at the big box stores. With the Lowe's or Home Depot versions, you can only cinch the metal female connector nut down over the male PVC to a depth of two threads before bottoming out.

To me, that was horrifyingly bad engineering.

With the ACE version, you get three threads covered. Still nothing to brag about, really--but light years less scary than just two threads.

It was well after dark by the time we were ready to turn on the supply water. Since we're still on gravity feed (think zero pressure), it took a while to fill the tanks. Mine especially; for whatever reason, Pam's toilet tank fills in maybe five minutes. Mine takes closer to twenty.

It's not the piping; the run to my toilet is actually slightly shorter than the run to hers.

Most likely, it has to do with all these modern flibberty-gadgety tank-filling widgets through which the water must pass inside the tank itself. And most likely it doesn't matter. For now, having to wait a while between flushes can't possibly compare with going potty in bucket toilets and dumping the buckets daily.

And for later--meaning when I get around to hooking up the booster pump--25 or 30 psi of water pressure should speed things right up for both toilets.

Now...any leaks? Incoming, none visible.

[*Flush!]

Any leaks outgoing? Nope. Don't see any.

So: How do the toilets function? Was the Home Depot guy with the hat right? That is, did it turn out to be impossible to vent the system adequately without puncturing the roof?

HAH! No, not a bit of problem. The Oatey AAV vents the septic line beautifully. These toilets hurl the bowl contents out of the toilet and down the line! Perfect venting!

Happy campers at the Border Fort? Yes, you could say that.

Toilets by Fred.