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how do I put a toilet in my workshop?

Trevor Lambert | Posted in General Questions on

I will be building a workshop/garage/storage/storm shelter/barn at some point (was originally going to be this year, but I’m going to wait until the pandemic is over). I want to have a two-piece bathroom in there. At the same time, I hope to rough in enough under-floor drains to allow for a future full bath and kitchen, to allow for the potential of being an accessory dwelling unit at some point in the future. 

Where this starts to get complicated is that we’re on a septic system. In an ideal world, I’d tie the shop drain into the house’s septic tank. A couple of things make this pretty difficult. One is that the house is built up to a much higher elevation than the land where the shop will go. By eyeball, I’m guessing 3-4 feet. I could build the landscape up higher to equalize this, obviously (it will naturally go up at least a foot to account for under-floor insulation). But aside from being pretty expensive, there’s another problem that makes this option a complete non-starter, as far as I can imagine: there’s a driveway between the house and the future shop. I guess I could build that up, too, but then it starts to get ridiculous. My wife isn’t going to go for that. She’s not even in agreement with me on having a bathroom in the shop in the first place.

The other solutions I’ve thought up are:
1)composting toilet. Not a fan of this solution, as it doesn’t do anything for the future-proofing, and it doesn’t even get me a sink to wash my hands in. These things are not cheap either. If this is the only option, I’ll just do nothing.

2)Install a separate septic tank for the shop, and use a septic tank pump to deal with the elevation difference to the drainage field. Is there such a thing as a macerating pump that could actually be placed ahead of the tank? That would save me the cost and real estate of the second septic tank.

3)install complete septic system just for the shop. In a “cost is no object” context, this is obviously the ideal. Of course, cost is an object, especially given the difference of opinion mentioned above.

Anything I haven’t thought of?

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Replies

  1. Brian Wiley | | #1

    You might give an incinerating toilet a look—or a second look—as they may be a good fit.

    Apparently the newer models don’t sound like a howlitzer: https://www.treehugger.com/hot-poop-cinderella-incinerating-toilet-4858783

  2. Dick Russell | | #2

    "2)Install a separate septic tank for the shop, and use a septic tank pump to deal with the elevation difference to the drainage field. Is there such a thing as a macerating pump that could actually be placed ahead of the tank? That would save me the cost and real estate of the second septic tank."

    While there are macerating pumps that will break up and lift toilet effluent to a septic tank at higher elevation, doing that is frowned on by septic system designers. A septic tank depends on settling out solids to the tank bottom where much of the bacterial digestion process takes place. Breaking up the solids from a toilet into far smaller particles, some quite tiny, hampers the settling process and requires much longer residence time to get the same degree of solids removal. This in turn calls for a bigger septic tank, if designing a new system. Otherwise, the total solids content of the "clarified" liquid is higher and creates a potential clogging problem for the leach (aka drain) field.

    That leads me to think that your best design would include a separate septic tank, one with an overflow pump chamber, in which there would be a common septic pump with level control to move the liquid up hill to the leach field. Such designs are quite common in my area, where many residences are on lakefront slopes and draining by gravity to a leach field is not possible. Leach fields here must be at least 75 ft back from the lake.

  3. plumb_bob | | #3

    What about pumping to a tank and having the honey truck haul it away when needed? With low volume use the haul would most likely be infrequent and not too expensive.

    1. Trevor Lambert | | #4

      Are you suggesting pumping from the septic tank into a secondary tank? If so, would this tank be above or below ground? In either case, I could imagine freezing being a problem.

  4. Rick Van Handel | | #5

    If your local ordinance allows it, a stand alone holding tank just for the shop is a fairly reasonable option. This would also allow you to tie in floor drains, which ordinarily would be kept out of a normal septic system.

    What is the vertical difference in elevation between the house and the garage?

    Depending on whether your existing septic tank is 2 or 3 compartments, and filtered or unfiltered, might determine if a grinder pump setup would be detrimental. A grinder pump install with pump controls is probably more expensive than installing a small holding tank, so for a system that may not have much usage, it’s probably your best value option.

    1. Expert Member
      Malcolm Taylor | | #6

      The other benefit of a tank and pump chamber over a grinder pump is that when things go wrong, the problem is out in the yard, not in your basement.

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