Tub Overflow and Drain Question

[NTM5]

I am putting in a new bathtub and whoever built the house did the plumbing wrong (I think).

The bathtub drain drains vertically into a p trap. The overflow drains vertically until floor level where and 90 degree connection diverts the water horizontally toward the tub drain. Its basically the opposite of the normal setup. It's hard to describe, but I already took it apart so I don't have pictures. But I'll attach a crude drawing.

Is this a problem? I

 

[breplum]

I have seen at least one mfr. make a W/O that looks like your drawing.
It is non-standard, but, since they manufactured some, should be ok.

 

[Zanne]

There's nothing wrong with it. What you're describing is a direct drain configuration. Sometimes it is done if floor joists or other obstructions are in the way. Sometimes it's because there isn't enough clearance & they need the tub shoe to drop lower but couldn't find the right parts to extend it down. Other times it's to give a straighter path for snaking the drain.
They sell direct drain kits & modular kits to allow for this configuration. I actually need to change one of my tubs to have direct drain because the people who did the reno on my house before we bought it cut all the way through a joist for the tub's P-trap.
The upside of this configuration is that the tub can drain a little faster since the water goes straight down instead of hitting an angle. Downside is if you drop something down the drain it may be harder to retrieve.

Keeney makes a modular kit that illustrates the different drain types (standard, direct, & back drain) 70W | Bath Drain Triad Lift & Turn | Installation Instructions | Keeney | PlumbPak
I believe Jones Stephens also makes a direct drain kit.

 

[Zanne]

Accidentally replied instead of editing. Oops.