Pitch on Line Penetrations

BACK

Pitch on Line Penetrations

By JD Kelly Bryan Orr

October 6, 2026

Most techs and installers know that drains need to be pitched. I use the rule of thumb that drain lines should generally be pitched 1/4″ per foot of horizontal run. One thing that can easily be forgotten is pitching wall penetrations when drilling.

*The outdoor end of the hole sits lower than the indoor end. The indoor head covers the hole from inside.*

It's as simple as drilling with a slight upward angle if drilling from the outside or angled slightly downward from the inside. The goal is to have the outdoor side lower than the indoor side, both to assist in draining system condensate and prevent exterior moisture from running into the building.

*Slight upward angle from the outside, slight downward angle from the inside. Both end with the outdoor side lower.*

*Slope it toward the inside and water runs into the wall. Slope it toward the outside and water runs back out.*

You will also want to make sure the drain doesn't run above copper or go up and down for any other reason. That is especially common in ductless systems with flexible drains. Keep that pitch moving in the right direction from start to finish, and all will be well.

*The drain rides below the copper through the wall and keeps falling from start to finish.*

—Bryan

Illustrations by JD Kelly

Work through this with the trade.

Highlight a short passage, or bring a question about a specific moment into HVAC No Bull Forum.

Discuss this reference → Related forum discussions

#drain pitch

Check out our most recent video

How to Evacuate an AC system, Full Vacuum Procedure

Our latest Podcast

HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

In this short podcast episode, Bryan talks about the fuse that only blows when you leave. The service call usually goes like this: you replace a blown fuse, the system runs fine, you leave, and then the fuse blows again. There could be several causes of a blown fuse.

First, ask what was happening right before the system stopped, such as if the unit was starting up, if it was raining outside, or if the operating mode changed. The customer may not know the specifics, but they may be able to offer a clue. If the control fuse blows during a specific call, we may be able to locate a short in one of the circuits involved. We may also be able to find out a bit by inspecting places where wire often gets damaged, such as common points where conductors pinch or rub.

Isolation diagnosis can help us isolate the specific circuit or component with a problem. First, look at the wiring diagram, label conductors, and take pictures of the original setup before disconnecting anything. Keep the correct fuse protection instead of using a larger fuse, leave all safety controls in the circuit, and use the manufacturer’s test procedure if it’s available. Then, isolate different loads and conductors so they can be energized individually; some modern thermostats make this easy. Also note that continuity testing alone isn’t always reliable for locating problematic paths.

Sometimes, motion (from motors), temperature, and moisture can also contribute to intermittent issues. Additionally, some inductive loads, like contactor coils, experience unique intermittent issues that cause the components to draw high current; inductive reactance matters. Measuring current on the different circuits as you energize them can also point you toward circuits that have higher current than expected.

Once you’ve found and repaired something, go back to the condition that made it fail. Make sure you fix the underlying problem, such as exposure to excess heat, vibration, or moisture.

This episode contains embedded sponsor messages from Refrigeration Technologies, Carrier, Fieldpiece, TruTech Tools, and Filtrete.

Resources

Purchase your tickets or learn more about the 8th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

Search Episodes

The Fuse Only Blows When You Leave – Short #307

10/13/2026

Bryan Orr

Questionable CO Alarms w/ Bill Spohn

10/08/2026

Bryan Orr

Same Charge, Different Numbers – Short #306

10/06/2026