I've just replaced my water heater and for the first time my house has a water heater drain pan. The washing machine waste line is nearby and I'd like to connect the water heater drain pan to this line before the trap. The proposed addition is shown in black:
The only pitfall I can think of is that if there's a blockage downstream of the tee, the washing machine water can back up into the black pipe instead of having to build all the way to the top of the green pipe.
Keeping in mind that the picture is not to scale, how can I determine what distances are safe for this configuration? If the trap were ten feet below floor level, would this be considered safe? Are there other issues I'm not considering?
The alternative involves a 12' run to a sump pit. This would crowd my crawlspace with a long, low drain line and might interfere with a future radon mitigation system connected to the sump pit. Please suggest another alternative if you have one.