heat trace within storm drain? what happens if a plumber snakes it?

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malachi constant

Senior Member
Location
Minneapolis
Our mechanical engineer specified heat trace to be installed within the underground storm on a commercial building. The electrical inspector is concerned that when a plumber snakes the pipe he will get electrocuted. I figure the ground fault protection would keep that from happening, but admit that it is very possible the pipe gets snaked someday, and that the likelihood of heat trace coming out from that unscathed is not very good. What is common practice for heat trace installed in underground storm drains?
 
gadfly56

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Frost Depth?

Frost Depth?

An underground sewer line, of whatever size, should be installed below the local frost line. You should never need heat trace in such a line.
 
charlie b

charlie b

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Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
It's a storm drain, not a sewer line. I spoke with a mechanical engineer about this issue. He didn't say putting heat trace inside a pipe was the stupidest idea he had ever heard, but it was right up there with the best. The idea of having to snake out the pipe was not his concern. He was more concerned with the impact on fluid flow, and the difficulty of installing the heat trace inside the pipe in the first place. He has seen cases of undergound pipes getting heat traced. Once was a long drain from a kitchen to a waste water processing area. The reason for the heat trace was not freeze protection, but rather to prevent grease from solidifying within the pipe. He also said there were times that he could not get the pipe below the freeze layer, and did put heat tracing on an underground pipe. But that was on the outside of the pipe.
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
Depending on which article this installation falls under signage is required.


426.13 Identification. The presence of outdoor electric deicing
and snow-melting equipment shall be evident by the
posting of appropriate caution signs or markings where
clearly visible.
Click to expand...

427.13 Identification. The presence of electrically heated
pipelines, vessels, or both, shall be evident by the posting
of appropriate caution signs or markings at intervals not
exceeding 6 m (20 ft) along the pipeline or vessel and on or
adjacent to equipment in the piping system that requires
periodic servicing
Click to expand...
 
George Stolz

George Stolz

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Location
Windsor, CO NEC: 2017
Occupation
Service Manager
Would the presence of heat trace cabling be considered...marking?

That's a new one on me, and thanks to Bob, I'm going to have a harder time sleeping at night. :ashamed1:
 
kwired

kwired

Electron manager
Location
NE Nebraska
gadfly56 said:
An underground sewer line, of whatever size, should be installed below the local frost line. You should never need heat trace in such a line.
Click to expand...
OP is talking about a storm drain and not a sewer line. That said I have encountered many sewer lines - generally for private septic systems, that are not below the local frost line, but they never give any problems with frost as they are sloped and the water doesn't sit there long enough to freeze. Completely different ballgame than a water supply line which will freeze if it doesn't have constant flow in freezing conditions because water is always present in that line.

charlie b said:
It's a storm drain, not a sewer line. I spoke with a mechanical engineer about this issue. He didn't say putting heat trace inside a pipe was the stupidest idea he had ever heard, but it was right up there with the best. The idea of having to snake out the pipe was not his concern. He was more concerned with the impact on fluid flow, and the difficulty of installing the heat trace inside the pipe in the first place. He has seen cases of undergound pipes getting heat traced. Once was a long drain from a kitchen to a waste water processing area. The reason for the heat trace was not freeze protection, but rather to prevent grease from solidifying within the pipe. He also said there were times that he could not get the pipe below the freeze layer, and did put heat tracing on an underground pipe. But that was on the outside of the pipe.
Click to expand...
I would like to think that a storm drain with a heat tape in it is designed that way to keep it from backing up during periods of "low flow" where the underground portion may freeze solid. Otherwise as far as restricting flow, that is going to happen during maybe a heavy rain, and will be during the heaviest rains the thing was designed for. One little cable in there probably isn't going to have much impact as long as it doesn't become something that causes other debris to get lodged in the line. If it has an effect on flow during such an event the drain is undersized, or you have a rain event bigger than ever anticipated and would have had problems anyway. JMO.

We had a backed up storm drain issue that caused flooding inside a hospital in a nearby city, the problem wasn't that the drain maybe couldn't handle the amount of water, but the storm happened to dump a bunch of large hail and the hail plugged the inlets to the drains and caused the flooding.
 
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cowboyjwc

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
For bigger pipes like sewer, our city doesn't snake them out, but they have vacuum trucks that pump it out, but they still have to run a hose down there so they could still affect the heat trace.
 
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malachi constant

Senior Member
Location
Minneapolis
thanks!

thanks!

The amount of knowledge on this board blows my mind. I tell architects and other engineering disciplines about this place and they think I am greatly stretching the truth as to the diversity, accuracy and promptness of replies. Incredible resource. Thank you all for contributing to this thread and others!
 
kwired

kwired

Electron manager
Location
NE Nebraska
cowboyjwc said:
For bigger pipes like sewer, our city doesn't snake them out, but they have vacuum trucks that pump it out, but they still have to run a hose down there so they could still affect the heat trace.
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I still don't see any reason to put a heat tape in a sewer pipe, and especially in your city. OP is talking about a storm drain, and chances are he is in a location where it will freeze. That means when temps at the surface are warm enough to thaw the temp below is still below freezing and the drain is plugged with ice, the heat tape assures at least a small passage through the ice for runoff to still be able to go through the drain instead of pooling up at the inlet.
 
cowboyjwc

cowboyjwc

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Staff member
Location
Simi Valley, CA
kwired said:
I still don't see any reason to put a heat tape in a sewer pipe, and especially in your city. OP is talking about a storm drain, and chances are he is in a location where it will freeze. That means when temps at the surface are warm enough to thaw the temp below is still below freezing and the drain is plugged with ice, the heat tape assures at least a small passage through the ice for runoff to still be able to go through the drain instead of pooling up at the inlet.
Click to expand...

Storm drain, sewer pipe, pretty much the same difference except for where they end up. Hey it got down to 60 last week. I'm pretty sure I know how it works too, my brother lived in Alaska for years and had all kinds of great, "it was so cold....." stories.
 
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kwired

kwired

Electron manager
Location
NE Nebraska
cowboyjwc said:
kwired said:
I still don't see any reason to put a heat tape in a sewer pipe, and especially in your city. OP is talking about a storm drain, and chances are he is in a location where it will freeze. That means when temps at the surface are warm enough to thaw the temp below is still below freezing and the drain is plugged with ice, the heat tape assures at least a small passage through the ice for runoff to still be able to go through the drain instead of pooling up at the inlet.[/QUOTE

Storm drain, sewer pipe, pretty much the same difference except for where they end up. Hey it got down to 60 last week. I'm pretty sure I know how it works too, my brother lived in Alaska for years and had all kinds of great, "it was so cold....." stories.
Click to expand...

Outside of the fact they both typically are a tubular product intended to convey liquids, there are many times a lot of differences in their installation and the "sanitary" part is a much bigger factor in how the sewer pipe is installed, the storm drain is primarily conveying surface run off to a different surface, sometimes nearby sometimes far off, but is generally not discharging it into a restricted access collection point. The fact that many paved streets have "curbs" makes them an "open" storm drain to a certain extent, that water may periodically drain to a below ground tube but the idea of the curb is to keep runoff from the street from running onto nearby properties.
Click to expand...
 
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G

GoldDigger

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Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
And since sanitary drains must accept input from basement level while sanitary drains need only accept surface water or pumped water the latter do not need to be as deep.

Tapatalk!
 
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