I am planning on turning a room in my finished basement into a bathroom. I am planning on using a macerating toilet. I have read on this site that they are not popular with everyone. However, I don't have the ceiling height for a Quik Jon, and I am afraid of groundwater issues if I bust up the floor and bury an ejector pump.

I am not a professional plumber, but I am not afraid to do the job myself. As I was researching and planning, I found that it is necessary to do DFU calculations in order to determine whether the existing drain system and vent system can handle the additional fixtures. Apparently, a very large number of DFUs must be assigned to a macerating toilet (2 X the flow rate in GPM). This works out to something like 46 DFU for the saniflow
If the information is true, it seems like it would eliminate macerating toilets as an option for anyone who has 3" drain lines instead of 4". Is this true, or am I misunderstanding the DFU calculation?

Thank you for your time,
Andrew



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i believe code says 2 DFU for each GPM pumped.
discharge rate varies with the height/resistance pumped.
saniflo says at 15 feet it pumps 17 GPM
so 17 x 2 = 34 DFU
at 3 feet it pumps 27 GPM
so 27 x 2 = 54 DFU
3 inch pipe will accept 48 DFU.

realistically, you are only pumping about 1.5 gallons.

Have you picked a specific pump? 2018 IPC states -

405.5 Plumbing Fixtures With a Pumped Waste

Plumbing fixtures with a pumped waste shall comply with ASME A112.3.4/CSA B45.9. The plumbing fixture with a pumped waste shall be installed in accordance with the manufacturer's instructions.

I believe 702.2 of UPC applies here:

702.2 Intermittent Flow. Drainage fixture units for intermittent flow into the drainage system shall be computed on the rated discharge capacity in gallons per minute (gpm) in accordance with Table 702.2(2)

Up to 7.5 gpm equals 1 DFU.

You should be worrying more about finding a proper vent (or a future vent)in the basement than anything else. If you don't have one your going to have to find one up stairs...behind the walls or sending one up thru the roof.

Response to packy.

Thanks. I thought that a 3” horizontal drain pipe can only accept 20 DFU? There is a drain pipe in the ceiling of the room that I was hoping to tie into. However, since I believe this pipe already has 14 DFUs assigned to it, I don't think this is an option. Instead, if I can make it work, I think I have to go all the way to the drain pipe that exits the house. I am hoping that pipe is a 4" pipe.

When you say “realistically, you are only pumping about 1.5 gallons", you’re saying, this probably isn’t an issue? That was sort of my thought. It seems like the code is pretty severe. This is also not a bathroom that is going to get a whole lot of use... but I do want to get my work inspected, and so I am assuming that an inspector would fail me if I am overloading a drain pipe.



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Response to NP16.

Thanks, yeah I did see this section. I believe the saniflo toilet that we would use will be at about 23 GPM at 8 ft.

Response to NoHub.

I believe I found a vent pipe nearby. I believe it is a vent pipe for a toilet on the floor above. However, it sounds like the DFU calculation applies to both drain pipes and vent pipes? So if I understand correctly, I need to run a separate vent for my macerating toilet. I believe I am going to be able to do so by running up through 2 closets that line up on the first and second floors, although this will certainly be a pain.

Second response to NoHub.

Ok, wait a minute. I just realized that I think I was misreading Table 906.1 of the IPC code. The vent pipe that I think I found (not 100% sure it is a vent pipe, probably 80% sure) is a 2” pipe. It is venting a 3” horizontal drain. Just downstream of the connection of this 2” pipe to the 3” horizontal drain is the connection of the 1st floor toilet. Anyways, according to Table 906.1 of the IPC code, a 2” pipe vent can handle 102 DFUs and run 86 ft high. Am I interpreting that right? The pipe runs through 2 stories and then the attic, so nowhere near 86 feet high. So I should be able to tie in here, right?

you can tie into a vent pipe as long as your tie in point is 6 inches higher than the flood rim of the fixture that vent pipe serves.
so even though that pipe you are looking at is in fact a vent for the toilet, you can not tie into it unless the tie in point is 6 inches above the height of the toilet bowl.

i would contact the inspector concerning draining the new toilet into the available 3 inch bathroom drain.
yeah, you technically exceed the limit but your chances are better at hitting the lottery than the chances of the toilet, sink, tub/shower and toilet pump running at simultaneously.

ct1818,The Plumbing inspector is not going to give a rat's tail about the Dfu's. A macerating toilet is a closed system and a different animal than a regular bath group and don't worry about the length of the vent either. If your going to do this your self at least hire a Licensed Plumber to find (or install) the Prober vent for that Macerating toilet. It's all in the venting of these units if you want to get years of performance.it won't end well if you cut corners.



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