Basement Sewage Pump Venting Requirements, Revisited

19 years ago

"The more I know, the less I understand" to quote lyrics from Don Henley.

While walls are open for a main floor remodeling, I want to add plumbing vents to support a future basement bath. The future bath would have to pump the sewage up to the drain line.

The Michigan Residential Codes 2003 apply, based on the IRC 2003.

Thanks to a suggestion from Lazypup a few weeks ago, the drain connection is all good. Venting has me befuddled.

Code differs depending on whether the pump is pneumatic or not. If pneumatic, a dedicated vent through the roof is required, sized based on the air requirements of the pump. Otherwise, it appears that the pump can be vented like anything else -- it can tie into existing vents and be half the diameter of the line it serves (but at least 1.25").

Question: For the pump, is the vent serving the typical 2" discharge line, or the 4" line it pumps into?

Lazypup suggested awhile ago that I install a dedicated thru-the-roof 1.5" vent for the pump (plus a second 1.5" regular vent for the fixtures, which is now installed). I'd prefer to tie the vents together in the attic if code will allow it.

Question: Are sewage pumps typically pneumatic? Or does the IRC 2006 (not yet adopted in Michigan) require a dedicated vent regardless of pump type? (Lazypup, if you're listening, perhaps you can clarify the dedicated vent suggestion better than anyone.)

The local big blue box store sells Star Systems .4 HP flush-up unit that has a 2" discharge and a 3" vent. A company tech support guy said that a 2" vent is okay where code allows it, but that 1.5" would not meet the company's requirements for proper operation of the pump. Of course, the same guy thought I was mistaken about "pneumatic" and "sewage pump" having anything to do with each other as one moves air and the other moves liquid. At least he was certain that their pumps are not pneumatic.

I've also seen a suggestion that a sewage pump vent be one size larger than otherwise required -- 2" instead of 1.5" in the post. If 1.5" is sufficient, I'm not sure what is gained by going larger. 1.5" would be easier to install, but I'm leaning toward using 2" just in case either the pump or the inspector requires it.

Question: What size vents are typical for sewage pumps in Michigan? Thanks in advance to anyone who can help clear the water.

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Comments (5)

lazypup
19 years ago
A pneumatic sewage ejection pump is a pump that is propelled by high pressure air instead of electricity. In which case the vent would be required to convey both any sewer gasses present in the sewage ejector crock and the exhaust air from the air propulsion system.

While pneumatic pumps are commonly used in commercial or industrial applications I don't recall ever seeing one in a residential environment. The problem would be that you would need a substantial air compressor to provide the necessary compressed air to operate the pump.

In regards to venting. The fixtures which drain into the sewage ejector crock are required to be vented in the usual manner and the fixture vent may be combined with the existing vents system.

A sewage ejection pump crock is required to have a separe vent which must terminate through the roof and it MAY NOT be combined with the DWV venting system.
michgeo
Original Author
19 years ago
Lazypup,

Thank you for the expert help. With your answers to my and other posts, I've been able to make better sense out of the text and tables in the code book. I see now, for example, that a 1.5" vent for the sump crock is fine for my application, with less than 40' of vent and a properly sized pump. (I now plan to avoid the self-contained flush-up units in favor of under-slab drainage into a traditional crock.)

Correlating the helpful advice with the code book gives me the confidence to proceed. But I've been unable to find the requirement for the dedicated vent for the sump crock (except for a pneumatic pump).

Could you explain a little further where the requirement comes from?
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lazypup
19 years ago
IRC minimum vent for the crock is 1-1/4"
Ref: IRC-T3113.4.1

UPC minimum vent size for the crock is 1-1/2"
UPC 710.10

The crock vent must terminate through the roof and it may only serve the crock. It may not be combined with other vents in the structure.

All fixtures discharging into the crock must be vented in accordance with standard venting requirements before they discharge into the crock.
bus_driver
19 years ago
The State of NC uses the 2003 IPC with State amendments. A quick reading of 916.5 indicates that sumps (crocks) for pneumatic systems must be vented separately. Separate vents for pump-emptied sumps is not mentioned. All this points to the necessity to learn the local code requirements for your installation.
michgeo
Original Author
19 years ago
I am grateful for the expert advice. I have the current Mich Res Codes book, but not the original IRC codes on which it is based. If I seem confused, it may very well be because of Mich amendments. It helps me a great deal, then, to know which sections of the IRC are being cited for comparison to the Mich codes.

I must confess that without the generous help of Lazypup and others, I'd go nuts trying to understand the codes just by reading the book. More than once the advice has either made the code book easier for me to understand, or it steered me to a different section that was more relevant to my question.

I've been able to correlate all other advice precisely to the Mich codes. But I still haven't found the requirement for the dedicated crock vent in the Mich codes. I suspect it's because I'm looking in the wrong place or missing some other subtlety. For example, is it because the sump crock drains independently into the 4-inch house drain that it should also have an independent vent? Is there a specific paragraph in the IRC that is completely absent from the Mich codes?

I found a discussion on the issue at the link far below, but it doesn't build my confidence one way or the other. "Homebild", who says that he/she is an "ICC certified Residential Plumbing Inspector", asserts that the IRC allows non-pneumatic ejector pumps to be tied into existing vents. He/she cites the same sections of the IRC that I find in the Mich codes. Specifically:

P3113.4.1 IRC 2003: "Drainage piping below sewer level shall be vented in a similar manner to that of a gravity system." [I don't have it with me, but the Mich book precedes this paragraph with something like 'For non-pneumatic sewage pumps and ejectors".]

P3113.4.2 IRC 2003: "The air pressure relief pipe from a pneumatic sewage ejector shall be connected to an independent vent stack terminating as required for vent extensions through the roof". [The Mich book precedes this paragraph with something like "For pneumatic sewage pumps and ejectors".]

By comparison, "Phil H" notes that amended New York State code explicitly inserts the word 'independently':

P3113.4.1 Residential Code New York State: "Drainage piping below sewer level shall be vented independently in a similar manner to that of a gravity system."

I'd still like to know where the dedicated vent requirement is found in the IRC, but you're right, bus_driver, I'll ultimately have to cut through the roof if the local inspector requires it whether or not I understand it.

Here is a link that might be useful: IRC Ejector Pump Venting Discussion