Garage Plumbing Septic System

[600SL]

I'm planning on building a Garage about 200' from my house. And no wheres near a septic system. In any case the concrete contractor recommended I at least put in a toilet flange before pouring. Sounds like a good idea but with toilet, I might as well put in sink plumbing. And of course for both of those I will need a water supply. So in order to do what he proposed. The attached pictures are what I came up with.

The third picture shows the plumbing system without the foundation. All the blue and red pipes are what I intend to install now before the foundation is poured. The rest will be added if I decide to install a toilet and sink.

The red pipe is actually just a 2" PVC conduit. I would like to use that conduit to feed pex water line through. That will make it somewhat easy to repair in the event of a freeze.

So a couple of questions.

1) Does this look reasonable.
2) What size pipes to use. I see 3" and 4" toilet flanges. Is 4" better than 3"?
3) Hows my venting schem look? Vent pipe has to be outside the building.
4) What size vent pipe is required for just a toilet and 1 sink?
5) If I were to eventually put a legal septic system in, what are the options?

 

[larry4406]

I didn’t study your pics, sorry. Hard to see on phone.

When roughing a toilet in concrete it’s easiest to use a 4x3 reducing elbow. 4” stubs up above concrete then 3” groundwork’s. Or use 4” groundwork’s if you prefer.

The hub on a standard toilet flange fits inside a 4” pvc pipe so it’s a breeze to set the toilet later. Install finished floor, cut 4” pipe flush to floor, radius the inner edge of the cut 4” pipe slightly and then glue flange in place.

Stub your groundwork’s outside. I would rough the full bath. Later install an Environmental One pump outside and pump it to your septic system; they pump insane distances and a ditch witch is your friend for its 2” discharge line.

Use long radius conduit elbows for the water line. Our water lines are 1” black poly so go big on conduit.

 

[Metal-Marc]

A friend had a burried steel drum topped with a Pontiac hood as his main septic system.

 

[600SL]

A friend had a burried steel drum topped with a Pontiac hood as his main septic system.

In my last garage, I had a water less urinal, plumbed to a 5 gallon bucket in the ground filled with rocks. For this garage I'm looking for something more legal.

The old house where where I grew up used Cesspools. They were just an empty cylindrical perforated concrete structure with a clean out cap on top. I don't see those anywhere any more. Seems I could use a small one for just a toilet and sink? Are they still a possibility?

 

[600SL]

I didn’t study your pics, sorry. Hard to see on phone.

When roughing a toilet in concrete it’s easiest to use a 4x3 reducing elbow. 4” stubs up above concrete then 3” groundwork’s. Or use 4” groundwork’s if you prefer.

The hub on a standard toilet flange fits inside a 4” pvc pipe so it’s a breeze to set the toilet later. Install finished floor, cut 4” pipe flush to floor, radius the inner edge of the cut 4” pipe slightly and then glue flange in place.

Stub your groundwork’s outside. I would rough the full bath. Later install an Environmental One pump outside and pump it to your septic system; they pump insane distances and a ditch witch is your friend for its 2” discharge line.

Use long radius conduit elbows for the water line. Our water lines are 1” black poly so go big on conduit.

Good info Thanks.

The Environmental One pump sounds good. Any idea on the cost of that system. It would be about a 300' level run to my septic tank.

I was planing on using 3/4 Pex for the water line. The conduit is 2" PVC. The bend radius of the 2" PVC is 9.5". Minimum bend radius for 3/4" PEX is 7" or 9" for 1" PEX.

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[larry4406]

I’m not up to speed on E-One pricing. Not cheap but I think they are the gold standard.

My experience with them has been on force mains on municipal sewer systems. They were spec’d specificity with no alternate.

 

[Northislander]

I didn’t study your pics, sorry. Hard to see on phone.

When roughing a toilet in concrete it’s easiest to use a 4x3 reducing elbow. 4” stubs up above concrete then 3” groundwork’s. Or use 4” groundwork’s if you prefer.

The hub on a standard toilet flange fits inside a 4” pvc pipe so it’s a breeze to set the toilet later. Install finished floor, cut 4” pipe flush to floor, radius the inner edge of the cut 4” pipe slightly and then glue flange in place.

Stub your groundwork’s outside. I would rough the full bath. Later install an Environmental One pump outside and pump it to your septic system; they pump insane distances and a ditch witch is your friend for its 2” discharge line.

Use long radius conduit elbows for the water line. Our water lines are 1” black poly so go big on conduit.

I agree with everything Larry has recommended here only thing I would do different is not extend the 4" above slab level. I would stop 1/2" below top off slab put a 4" poly test cap on. this way the cement finishers can trowel right over toilet location with the result being a flatter floor. When you decide to do toilet chip out the 1/2" of concrete cut test cap with a utility knife and install closet flange. I find especially on shop slabs that the concrete finishers always screw up the finish at a projecting pipe.

 

[600SL]

I agree with everything Larry has recommended here only thing I would do different is not extend the 4" above slab level. I would stop 1/2" below top off slab put a 4" poly test cap on. this way the cement finishers can trowel right over toilet location with the result being a flatter floor. When you decide to do toilet chip out the 1/2" of concrete cut test cap with a utility knife and install closet flange. I find especially on shop slabs that the concrete finishers always screw up the finish at a projecting pipe.

I like the idea. Also, can a toilet flange be set flush to the concrete slab, or does it need to be on top of the slab.

Looks like I can do the same thing with the sink if I put a 2" coupler at the end of the sink tube.

 

[Northislander]

I like the idea. Also, can a toilet flange be set flush to the concrete slab, or does it need to be on top of the slab.

Looks like I can do the same thing with the sink if I put a 2" coupler at the end of the sink tube.

I have done the 2" just under the surface i use a 2" poly test cap on pipe the wrap with sill foam gasket to leave room for cplg. to glue on later. Toilet flange could be set flush with concrete slab but should be on top with anchors drilled in and one wax seal. with flange set flush you will need a spacer flange and or two wax seal or a max wax seal.

 

[600SL]

I could easily attach a 3/8" thick plywood disk to one of those temporary plugs to make room for a flush toilet flange. But would the spacer flange or double wax, max wax be more problematic?

For the 2" pipe I could just permanently set a 2" coupler 1/2" below the surface. I cant get a plug for the 2" female coupler end, at least not that I'm aware of, but could cut a short 1" length of 2" pipe and put a slot in it and then use a 2" plug.

 

[larry4406]

Ideally your want your finish floor to be flush to the underside of the toilet flange. This ensures proper "crush" of the wax ring. Cutting the stub off later flush to the finish floor ensures this and allows for proper engagement of the flange hub with the 4" pipe.

A competent concrete finisher should be able to work around a projecting pipe and keep the slab flat.