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2.101 -O- What prevents the FDD lateral discharge pipe from freeze ups?

Posted by Lori Byron on 30 Jan, 2014
Category: Category 2 - about potential recommendations

Frank Burdick’s Log Number: 88
Submitted by: Burdick log
Category (1,2,3): 2
Status: Open
Estimated date to address: N/A

2.101 FDDs and air gaps as currently designed are susceptible to freeze ups. During the recent extreme cold temperatures, water continued to flow into some sump pits and be discharged.  Many of the "air gap" locations were buried beneath snow drifts. What prevents the occasional pump discharge  water from ice build up on the inside of the exterior discharge pipe near the grade and below grade? Is the lateral pipe that takes the discharge to the curb, or other areas, buried below 42'?  (ie the frost line in this region.) If not what prevents this lateral from freeze ups? In your response, please consider the current code for allowable exposed plumbing vent pipes that vent thru the roof of a structure, as this code should apply equally to the FDD piping near grade. [Burdick 88; 1/12/14]

[CITY]

Water from sump discharges is typically around 50 degrees. The discharge pipe is installed with adequate slope, which prevents the water from standing and therefore freezing.

Comments

Frank Burdick on 31 Jan, 2014:

Unacceptable response.  Not enough consideration was given to current code regarding "at grade" or at roof line penetrations.  Why are roof penetration for vent pipe enlarged to 3 or 4 inches minimum..... Get that answer, and you will better understand the question.

Once again... who at the city provided this response and on what date?

 As per Mr Conen's comments at the 9Jan meeting. I would request that building officials come to the meeting to answer our questions concerning code issues.

Thanks

Frank Burdick on 31 Jan, 2014:

this question is NOT closed.

Jim Osborn on 31 Jan, 2014:

"Many of the "air gap" locations were buried beneath snow drifts."
I have an outdoor thermometer with a radio sending unit. I had been lazy and placed it on the ground on my patio. It worked great, recording temperatures down into the teens. But during the early January snow fall, it began to only record 31 degrees, even when it was zero outside. I thought "SNOW CAVE" and dug it up and placed it in the drip pan under my BBQ. As soon as I did so, it recorded a temp of 4 degrees.

I mention this because if an air gap is covered, it will be insulated and a large flow from a sump pump will not linger and it will have too much heat to freeze, especially if the air is only 30 degrees. So, being covered in snow is actually a good thing, as it eliminates any wind chill.

Frank Burdick on 6 Feb, 2014:


Do your research and learn WHY the following is a CODE requirement. Then apply your new knowledge to the current design of the Air gap of the FDD and the buried verical discharge line connect to the air gap location. This pipe can freeze up. The FDD design is flawed in this and many other ways. I will be addressing the Code officials on 12Feb14 regarding this and other code issues.
Michigan Plumbing Code:
R 408.30753a Roof extensions. Rule753a. Section 904.1 of the code is amended to read as follows: 904.1. Roof extension. All open vent pipes that extend through a roof shall be terminated at least 1 foot (305 mm) above the roof, except that if a roof is to be used for any purpose other than weather protection, then the vent extensions shall be run not less than 7 feet (2134 mm) above the roof. History: 1998-2000 AACS. R 408.30754 Rescinded. History: 1954 ACS 81, Eff. May 19, 1975; 1954 ACS 91, Eff. June 16, 1977 R 408.30754a Frost closure. Rule 754a. Section 904.2 of the code is amended to read as follows: 904.2. General. To prevent frost closure, every vent extension through a roof shall be a minimum of 3 inches in diameter. Any increase in the size of the vent shall be made inside the building a minimum of 1 foot below the roof or inside the wall. History: 1992 AACS; 1998-2000 AACS. R 408.30754b Extensions outside a structure. Rule 754b. Section 904.7 of the code is amended to read as follows: 904.7. Extensions outside a structure. Vent pipes installed on the exterior of the structure shall be protected against freezing by insulation or heat, or both.

Jim Osborn on 6 Feb, 2014:

"Many of the "air gap" locations were buried beneath snow drifts." and R 408.30753a Roof extensions. Rule753a. Section 904.1

These are two very different applications. An vent pipe for air through the roof is different from an intermittently used water pipe that drains that is near the ground, covered in snow.
 The FDD application is for water, and your question mentioned being buried by snow. Snow isolates it from any wind and can keep it from experiencing the very low temperatures. THE sump water is usually warmer,  50 degrees, and when the flow stops, the pipe is drained., leaving nothing to freeze. If any small amount were to freeze, the next pump discharge will melt away any small coating inside the pipe. .  The diameter is also fairly large, making it difficult for any ice bridge to form


The code rule 408.30753a that you post is for roof extensions, an empty pipe for air that connects to the sewer so that drains run freely. These differ in several ways from the FDD pipe. First, they are up on the roof, exposed to wind shill from air. Second, they only have air, so that warmer water from a sump cannot melt any ice bridge from it. Thirdly, the code requires the opening to be 3 inches so that moisture cannot fall on it, freeze and build up layers until it is blocked. While this could happen with a small ½ inch pipe, the code requires a much larger pipe to prevent this.


Look at all of the thousands of homes that have an exterior pipe added from the basement to the roofline that is for radon mitigation. The code addresses this differently , as I have yet to see any insolation on them. An air pipe through the roof is different from an intermittently used water pipe that drains that is near the ground, covered in snow.


Robert Czachorski on 6 Feb, 2014:

Jim - thank you for your comments. We are pleased to see a cordial, open dialog and discussion of the pros and cons of various ideas. You have identified several good considerations that would make sense to discuss with the building official. 

Frank - your last comment was inappropriate and I have removed it.  There is no need to use sarcasm and demean other members of the CAC.  This is the second time you have done this to Jim.  Charlie provided a warning the first time.  I think you should apologize to Jim.

I would like to remind everyone of some of the norms that Charlie asked the CAC to consider.  This will be a topic of discussion at the next CAC meeting.  

1.  Treat each other with dignity and respect.
2.  Listen first to understand, and don't be dismissive of input received when we listen.
3.  Support each other - don't throw each other under the bus to external parties.
4.  Avoid territoriality - try to think about what's good for your neighbors and the entire City.
5.  Come prepared to the meetings ... showing value and respect for the time and convenience of others.
6.  It's okay to be the messenger with bad news ... we will greet it with a problem solving approach.
7.  The discussion of issues, ideas, and direction will not bring about a personal attack and return to haunt someone in the future.
8.  Project team members (consultants/City staff) will be accountable and responsible to the CAC.

Take care,
Robert

Frank Burdick on 22 Feb, 2014:

Ok, I guess I am not the messenger of bad news this time.... read your local news...

http://www.mlive.com/news/ann-arbor/index.ssf/2014/02/ann_arbor_crews_digging_up_mad.html

My opinion/ theory/ concern about freeze ups of the sump pump discharge line was disparaged in the above comments.  

I stand by my concern.  

The FDD program as currently designed and implemented needs to be changed.