Gas pipe / black pipe slope

[dwplumbing]

As a DIYer, I did not do gas pipe work very often. I have noticed on some homes, the trunk run of a rigid gas pipe (black pipe) is sloped back to the meter. Is this a common practice to keep the pipes drained of water, etc? Also are the "drip legs" at each appliance used for the same accumilation because slope back to the main line is not possible in many cases at those locations?

 

[breplum]

From my knowledge, there is no slope requirement for slope.
Drip legs are required for multiple good reasons: moisture and debris
There can be lots of moisture in natural gas, I say this from experience.
I've had multiple instances of 'dead' gas line systems, where the liquid built up to actually block the line, making it unuseable until the water was removed.

 

[TomFOhio]

There is NO slope on the main gas line in the home.

 

[dwplumbing]

From my knowledge, there is no slope requirement for slope.
Drip legs are required for multiple good reasons: moisture and debris
There can be lots of moisture in natural gas, I say this from experience.
I've had multiple instances of 'dead' gas line systems, where the liquid built up to actually block the line, making it unuseable until the water was removed.

Makes you wonder why then there is not a "slope code" for gas lines since the water in NG should not be left in the trunk lines.

 

[TomFOhio]

I never took a gas line apart that had water run out. Dead lines that I got into usually had something taken
apart somewhere so moisture wasn't there

 

[CT18]

Gas should not have any condensation in it. It may have some thread oil left over but that's about it. Years ago we welded a o let into a compressed air line that had been shut down. The thread oil that had settled in the bottom of the pipe caught fire and burned up some equipment that was connected to the comp air line. We now purge any existing piping that we add a welded fitting too.

 

[sawsaw]

Gas should not have any condensation in it. It may have some thread oil left over but that's about it. Years ago we welded a o let into a compressed air line that had been shut down. The thread oil that had settled in the bottom of the pipe caught fire and burned up some equipment that was connected to the comp air line. We now purge any existing piping that we add a welded fitting too.

NG has plenty of water in it. My furnace kicks out plenty in the exhaust and the drain line.

 

[breplum]

This was at the bottom of a hillside home. So much water in the line to purge. Method: set up multiple tees, LHBV , test gauge with Schrader valve (with high psi range), isolate appliances and pressurize with air, then let loose.
View attachment 3494FC03-698B-404C-B150-C919E006A2E4.mp4

 

[wpns]

NG has plenty of water in it. My furnace kicks out plenty in the exhaust and the drain line.

Combustion products contain water. NG should not contain water, which is not to say it doesn’t.

 

[dwplumbing]

This was at the bottom of a hillside home. So much water in the line to purge. Method: set up multiple tees, LHBV , test gauge with Schrader valve (with high psi range), isolate appliances and pressurize with air, then let loose.
View attachment 38025

Maybe water in the NG lines are geographically dependant?

 

[CT18]

Maybe. I have been in many NG lines from 1/2" to 8" from houses to plants and no water.

 

[sawsaw]

NG has plenty of water in it. My furnace kicks out plenty in the exhaust and the drain line.

To clarify ... I should have stated water vapor, of which I have plenty in my NG.

 

[TomFOhio]

I guess I don't understand. That vapor is made from the furnace and not the gas line. If it was in your line your
pilot and burner tubes would have water in them and the furnace would shut down.

 

[sawsaw]

Here are a couple statements from articles on-line:
"When natural gas burns, a high-temperature blue flame is produced and complete combustion takes place producing only water vapor and carbon dioxide."
"Freeze-ups can happen. Pipelines freeze up, because of MOISTURE in the gas. Frozen equipment, power plants – STOP, just like that! We see the devastation that this caused in Texas
this week and is still occurring. In Texas, a warm climate, freeze-ups are not something that come to mind to worry about. However, look how quickly and how easily it can happen.
Natural gas comes out of the ground saturated with moisture. That moisture needs to be removed or it will cause problems. If the moisture is not removed, it will corrode burners, burn less efficiently, and in cold weather, the moisture will freeze and block the flow of gas."

When my NG furnace is functioning, it, the same as the A/C, removes the water from the gas during the combustion. I have icicles forming on the outside exhaust pipe - reaching the ground, as well as being collected in a furnace-mounted reservoir inside, which is pumped to the floor drain.

 

[CT18]

Because where it is cold we use these Deliquescent NG dryers

 

[sawsaw]

Because where it is cold we use these Deliquescent NG dryers

Not aware of that being used in the retail level. However, most likely in the pipeline at the source.

 

[wpns]

When my NG furnace is functioning, it, the same as the A/C, removes the water from the gas during the combustion. I have icicles forming on the outside exhaust pipe - reaching the ground, as well as being collected in a furnace-mounted reservoir inside, which is pumped to the floor drain.

Once again: You are confusing water vapor that's produced by combustion with water vapor that might be (but shouldn't be) in the NG in the first place. Water as a combustion byproduct is what's collected in your furnace to be pumped to your floor drain, and the water vapor that escapes the 'fully condensing' furnace is what's forming icicles on your outside exhaust pipe.