Drainage for two new baths

Hi,
I'm hoping to get some critique on the attached DWV mock-up I came up with for our new 2nd floor addition before I start tearing into walls.
The fixtures will include two back-to back bathrooms, a washer and a condensing hot water heater.

The mock-up is just the general arrangement. The pipe runs have been shortened to fit in the picture. The 2" horizontal drain will actually be 1 floor down and the 3" main drain will tie into the 4" sewer line in the basement.

The 3" vent will now serve as the main sewer vent to the roof, because this old 1 bath house only had a 2" main vent (and the existing W/C has always gurgled because it didn't have it's own vent!).

My specific questions are:

1. Does this look OK per UPC (Seattle)?
2. Any other clean-outs required?
2. Do I need a trap primer for the HWH drain (The drain is for a Polaris condensing HWH and a hydronic radiant system set-up)?

Any comments will be appreciated. Thanks!

Hazel

Plumbing lay-out

I see very little wrong with your lay-out. I can't comment on codes because they vary from state to state, and county to county. I would say that you need a trap primer on the floor drain. If you are running the 3in. in the ceiling of the basement I would add a cleanout. Your vents can be combined and tied into the stack at least 6in. above the highest fixture. Luck.

Thanks for the input

I do plan on "back-venting" the vents. I'll add another cleanout downstream but was concerned there were too many bends on the washer and HWH runs not to have a cleanout. Thanks!

The bends are fine, they go down anyway.

It's the horizontal bends that can add up.
After 135%, you add a cleanout.

Vents are revented at 6" above.
That 3" vent looks extra. I wouldn't need it in Washington.

Floor drain gets a trap primer and you're done.

Thanks Terry - question

The extra 3" vent. Can it be 2" then?

Hazel

Can you explain this trap primer bussiness? Gets a little float or something and when water goes down, it adds some? This typical in residential work?

Thx
Jason

Trap primer

For infrequently used drains, like floor drains, a trap primer is used to keep the trap from drying up and letting sewer gasses through. The one I plan to use is installed in-line on a frequently used cold water supply, and lets a little water out when it senses a small difference in pressure. The small amount of water is piped to the trap keeping it full.

From the responses I've gotten, it seems that it is required. It's a good idea anyway so I was planning on using one.