This question is relative to the California Plumbing Code (CPC), specifically the Sacramento area.

I'm doing some remodeling of a bathroom where the water heater pan drain line comes across the ceiling a bit lower than I can allow because I'm replacing a drop ceiling with hard and I'd like to get it up higher than where the pipe exits the exterior wall.

The drain is running parallel to the wet wall of the bathroom and therefore I have access to the building sewage drain system. Is it okay, per the above codes, to connect the water heater drain pan to the building waste system?

I've found an inspection checklist which says...

Drain-Pan shall be required when a water heater and/or tank is installed in a location where it could cause damage; in case of failure/leak to floor, sub-floor, drywall. Drain pan shall be installed with a minimum ¾” drain outlet and discharge that drains to the exterior of the building or an approved location. (2013 CPC Section 508.4)

...so being that the heater itself is in the attic space I have to follow this rule. But when it says (emphasis mine)...

"that drains to the exterior of the building or an approved location."

...I'm not able to find where in the code it defines approved locations. Can anyone shed some light on this issue please?

  • 1
    I'm not sure, but I think you need an air gap for the drain pan. If true you could not connect it directly. Also be cautious about making a hole in a horizontal drain pipe - you might be letting drain water out.
    – Ariel
    Commented Jan 12, 2015 at 1:41
  • @Ariel, I'm not sure of the air gap for the drain pan, the pressure valve does need one in the same room as the valve, but I'm not sure, as it seems uncommon to attach it to the waste system, it would be necessary. It also seems excessive for my specific situation due to the fact it would be ~3-4' above any open drain in the house. So, even if the building system was completely stopped up there's no way it could fill to that level. But it does raise a good question do to the fact the pressure valve doesn't either and codes are written for the general, not specific, case. Commented Jan 12, 2015 at 8:28

3 Answers 3


Your local Building Commissioner, should be more than happy, to answer this question. In most cases, a trapped drain pan is fine, but a pressurized relief valve is not - as it could disrupt other houshold traps and/or blast high pressure/high temperature water, down the drain, and back up another trap, if not permanently damage parts of the sewer lines.


An Approved location that I'm aware of is like a Floor Drain. Though Ariel is Correct, you would need an Air Gap. So the pipe would have a 1" min Gap to the Drain so that any back flow of water could not touch the exit pipe. The Main issue here is keeping the sewer gases in the system and not outside. This is what the p-Trap is for. Its a water barrier to prevent sewer gases from escaping the system. The Water Heater Drain pan does not typically have water and any p-Trap installed in that line would not have any water in it to fill the p-Trap.

My HVAC system is in the Attic and it sits in a large drain pan so if the AC leaks water will drain out. They plumbed the 3/4" PVC drain to a Soffit vent over a window. The purpose for the over the window was it would be obvious to someone that there was a leak.

Hope that helps.

  • I do believe you're correct on the "approved area". I think it means any indirect waste receptor, so floor drain, wash sink, mop area, etc. The problem with the air gap, and this is just opinion, is the drain pan is gravity fed. Most instances of an air break/gap involve pumps - pressure valves, dishwasher drains, and washer machines. I don't see where the cross contamination comes when you're dealing with gravity fed drain not directly connected to the unit. IOW, if the pipe was filled, it would overflow the pan, not contaminate your potable water source. Commented Jan 12, 2015 at 8:32

I believe you could tie into the vent as long as you increase the pan drain size to min. 1 1/4" and install a trap seal primer. other option would be to run the pipe into the crawlspace (if present) and tie into a floor drain trap. otherwise you need to discharge it indirectly with an air gap

  • 2
    Why do you believe this? Is this something you read about, saw performed by a professional, etc.?
    – wallyk
    Commented Nov 27, 2016 at 18:20

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