Attaching a waste valve with bayonet fittings to a 3" hole in a plastic tank?

[daveola]

I have a large plastic tank with a 3" hole in it that I put in one of these bulkhead fittings:

https://www.amazon.com/TF300-Polypropylene-Bulkhead-Fitting-Female/dp/B0079JUH6W

(I enjoy the fact that the 2 pack costs almost 10x a single unit  )

I did some fancy plumbing, but now I just want a waste valve, and I can't see a simple way to do it.

I can get a twist-on waste valve that has the bayonet and lug fittings, and I believe the lug side is supposed to be on the tank:

https://www.amazon.com/Valterra-T58-Twist-On-Waste-Valve/dp/B000BGHYJS/

But how do I get from the male 3" pipe thread on the bulkhead fitting to the lug fittings?  Seems like an easy job, nope!

I can easily find 3" MPT to 3" bayonet, but that's wrong on both ends:

https://www.amazon.com/Valterra-T1027-Rotating-Adapter-3-Bayonet/dp/B000BGK25G/

This is 3" MPT that claims to go to 3" bayonet, but it looks like lugs to me, so only one side is wrong here:

https://www.amazon.com/Valterra-T1029-4-Termination-Adapter-Bayonet/dp/B002N5PP8W/

I can find a "hub" (which I think means unthreaded and just needs to be glued to an ABS pipe directly):

https://www.amazon.com/Trailer-TERMINATION-ADAPTER-Connection-FEMALE/dp/B0933J9JJS/

Or this which claims "spigot" but I think is also a hub:

https://www.amazon.com/Trailer-TERMINATION-ADAPTER-Connection-FEMALE/dp/B0933J9JJS/

So I could just use a bunch of adapters, but:

1) Now the thing is starting to get extra long and sticking out further than I would like
2) More importantly - this is starting to make me think I must be doing something wrong or missing something.

So - what's the best way to get from a 3" hole in a tank to a 3" waste valve properly?

[daveola]

I found this, but the fact that it seems to be so non-standard and so hard to find still makes me think I'm doing something wrong.

Any thoughts on the best way?

https://www.etrailer.com/RV-Sewer-Hose-Fittings/Valterra/F02-2004.html

[richard5933]

Two thoughts...

1) Keep the bulkhead fitting you have, use a PVC mpt-to-glue on adapter, then a short piece of pvc, then a glue on a gate valve.

2) Swap out the bulkhead fitting for a 3" Uniseal. Then use a short piece of pvc with a glue on gate valve.

[Jim Blackwood]

Why doesn't the bulkhead fitting:

https://www.amazon.com/TF300-Polypropylene-Bulkhead-Fitting-Female/dp/B0079JUH6W

...work with this?:

Valterra - 1216.1011 T1029-4 Termination Adapter - 3" Bayonet x 3" Male Thread

Are you looking at the bulkhead fitting correctly? The end opposite the nut is the one with the 3" female pipe thread. The nut goes inside the tank.

Jim

[Dave5Cs]

How about a 3" Fernco fitting?

[Jim Blackwood]

A good choice, versatile, cheap, and widely available, carried by most hardware stores. Ace has a good assortment. Adds shock isolation to the tank and easy service. Also the Valterra dump valve has a wide variety of inlet and outlet pieces usually stocked by your local RV dealer. That's my first choice in waste tank plumbing. Usually not hard to find a matching combo. Good for vent lines too.

Jim

PS: A small hint. Ask to go upstairs to look at their Valterra fittings. If they do any service work at all what they have in the showroom is only a small fraction of their stock available to the mechanics.

Also, most waste tanks can have the fittings glued on. I didn't trust it until I tried it with new tanks. Worked fine, never leaked, and didn't fall off. PVC is commonplace, make sure it is the right glue. Flanged straight fitting, Fernco, and straight inlet Valterra with a twist lock outlet makes a nearly unbeatable combo. Different inlet sizes are available.

[Tedsoldbus]

I hope you figure it out. Your getting advice from those who know more than me. The guy who had my bus before me monkeyed with plumbing so he could do XYZ, and got the fittings sticking too far out as you mentioned. Now the septic anaconda won't hook to the barbed fittings and still make the turn to go through the hole in the floor. To dump, I have to hook up the hose from outside and leave the bay door open a bit. Looks very classy...!
I'd change it but he glued all the joints right at the next fitting. It is one of those "I need to fix that", but the left side of my brain says "Be careful what you start cutting. Put the sawzall away sir. Nobody has to get hurt here..."
I am sure you are staying away from that.

[chessie4905]

How about using one of those 90 degree clear ones to go through the floor?

[belfert]

I used a Valterra T1007 for connecting my waste valve to a 3" male NPT.  https://www.amazon.com/Valterra-T1007-Female-Thread-Flange/dp/B002N5J9OS

[Jim Blackwood]

Look hard enough you might even find a male thread version that will couple directly to your tank bung.

Jim

[belfert]

If you click on the Amazon link I provided you can choose from a male or female version of the adapter.