[joseph001]

What can a 3'',4'' and a 5'' pipe hold when dealing with toilets? What is the maxium number of toilets I can put on these three pipes?thanks.

[ballengerb1]

Is this residential or commercial application? 4" is usually the max I have used but most all of my work is residential

[massplumber2008]

Hi Joseph

Tricky answer...

Fixture counts differ from state to state, but in Massachusetts you can have a maximum of 2 toilets or 2 bathroom groups on a 3" horizontal fixture branch, or you can have a maximum of 3 toilets or 3 bathroom groups on a 3" building drain (or building sewer).

In terms of the other sizes you asked about you can't really assign maximum number of toilets... or at the least it would not be realistic because there are always toilets, sinks, tubs and other fixtures on the drain line.

However, for fun, I'll pretend, OK?

To begin, fixtures are calculated in terms of FIXTURE UNITS (FU).... Pitch matters here, too.

A residential tank type toilet is 6 FU

A commercial flushometer type toilet is 8 FU

A 4" building drain with an 1/8" pitch per foot of pipe can have a maximum of 180 FU

A 4" building drain with an 1/4" pitch per foot of pipe can have a maximum of 216 FU

A 4" building drain with an 1/2" pitch per foot of pipe can have a maximum of 250 FU

A 5" building drain with an 1/8" pitch per foot of pipe can have a maximum of 390 FU

A 5" building drain with an 1/4" pitch per foot of pipe can have a maximum of 480 FU

A 5" building drain with an 1/2" pitch per foot of pipe can have a maximum of 575 FU

So, as an example, for your question you could have a maximum of 65 residential toilets (@ 6 FU ea.) on a 5" building drain with an 1/8" pitch per foot of pipe (@ 390 FU), i.e. 390/6 =65 toilets max
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For a 4" building drain with a 1/8" pitch per foot (max. FU 180) you could hook up 30 residential toilets (6 FU ea.) max. i.e. 180/6 = 30 toilets

Again, that isn't realistic... would need to include fixture units for all the other fixtures in the building.

Questions? Let me know...

Mark

[Milo Dolezal]

Very well explained, Mark... Unfortunately, I was disallowed to leave a positive feedback for you.

[afaroo]

Mark,

You have explained it very well I am in the same boat as Milo would not allow me to give you a psitive feedback, Thanks.

John

[massplumber2008]

Thanks guys... I appreciate it! :)

[joseph001]

Thanks very much!