Heat pump water heater condensate drain and water softener back wash draining into same standpipe?

[TunaBreath]

Is it permissible to have the condensate drain from a heat pump water heater (5/8" tubing likely) and the back wash waste from the water softener set to discharge into the same trapped standpipe? If so, what size would be required, 1.5"?

Also, is an air gap fixture needed or could I satisfy air gap requirement by using a funnel drain and having the discharge set 1" or so from the top of funnel drain? I would eliminate the 5/8" tubing and use 3/4" PVC for both the water softener and condensate drain, securely mounting to the foundation wall using a90 deg elbow 1" above the stand pipe or funnel drain.

Or would my best course be to use two of the air gap fixtures below?

https://www.amazon.com/Plumb-Pak-PP...air+gap&qid=1616891274&sr=8-6#customerReviews

OR this:

https://www.supplyhouse.com/Tru-Gap-92534-Tru-Gap-Air-Gap-Fixture-w-1-Tubing-Mount-Bracket

 

[Breplum]

I would recommend two inch trapped drain with a typical four x two reducer as a funnel. Receptors are always two inch.
That unit from Supply House looks interesting, but crowded for the two 3/4" drains, esp. a high speed flush from a softener.
NOTE: I've never worked around water softeners, so not sure what backwash flow is.
You may be better off with a 12" x 12" receptor.

 

[Sponsor]

 

[Jeff H Young]

if the fitting is an inch above the stand pipe then you have an airgap. a 1 inch airgap is fine. an airgap fitting is not required