[HoosierDaddy]

Here ya go!

http://www.ipscorp.com/plumbing/watertit...ffset_ring

[Hotrodhornet]

Here ya go!

http://www.ipscorp.com/plumbing/watertit...ffset_ring

That sure looks like it should do the job!!!

[brian]

Why not stay with what you have? .

Well, I tried. I called a microphor distributor and was sent the wrong parts. I'm tired and I don't want to rely on air to flush a toilet. The technology is 20 years old and no major manfacurer is manfacturing an air operated or assisted toilet today.

[brian]

I just replaced mine last week. I got tired about worrying about having air pressure to flush the toilet.
I bought a flange for the floor that the toilet bolts to that required a 4" hole, I was able to drill the hole Offset from the original smaller hole to move it over about a 1".
That gave me enough room to mount the flange that bolts to the top of the tank, the flange on the tank   
Requires a 3" hole to be drilled in the tank, I was able to drill it straight down from the 4 " hole.
I drilled a 4" hole in a scrap piece of 3/4" plywood to use as a guide for the hole saw and screwed it to the floor where I wanted to drill the hole. Hopefully that will give you enough room.
It worked on mine. You call p.m. For my phone # if you want to talk about it.
We went camping at choke canyon lake last weekend and I am loving my new toilet. Paul

Thanks Paul for your insight and experience.

I have a 3 inch hole in the floor already.  I'm leaning to use the plywood guide trick and expand the current 1.5 inche waste hole by turning the hole saw by hand since there is not enough room to accomodate a drill.

Although, I wondered if one were to flush often enough, if one could attach 3 inch piping to the flange which runs vertically for 7 inches or so then tie into the existing 1.5 inch pipe that runs horizontally for 5 or inches so as not to deal with the existing tank hole. I know for a fact that my microphor did not have the recommended 60 psi (possibly 30 or less) and the effluent ran into the tank.  Does the hopper act as a mini macerator?

Yes, I do know the above proposed scenario is not to code.

[Richard]

In my opinion, running a larger waste pipe into a smaller one will result in an unpleasant issue sooner rather than later.

[folivier]

I think the hopper does act as a macerator using the air pressure to break stuff up.

[brian]

In my opinion, running a larger waste pipe into a smaller one will result in an unpleasant issue sooner rather than later.

I agree. I'm just trying to understand the mechanics of the flowing effluent.

[Hotrodhornet]

I would do whatever I could to make it drop straight down the 3" hole to avoid any blockage, when I get to my coach I will take some pics of the flange I used to bolt onto the top of the tank, the pipe slips into the flange just like assembling PVC pipe, I used the not hardening pipe dope in case I ever have to disassemble it for some reason. 
I went to the Texas r v in San Antonio and told the gentleman what I was trying to do, he had both flanges in stock, the hardest part of the deal was drilling the hole. Paul

[hagcam]

Last year I changed my microphor toilet to an RV drop toilet. One of the best changes I ever made. My old toilet worked okay, sometimes I would have to use the handle twice to get the toilet to flush. I didn't like that it used almost 2 litres of water every time it was flushed which wasn't a problem most of the time except when boon docking, the black tank would fill up first.

I drilled through the floor, (3/4" plywood, and sheet steel), then through the top of the bay (steel) and then into the plastic tank. I used 3' pipe, and the hole in the tank was slightly offset to the toilet hole. I used 2 45 degree elbows. It has worked without a problem. I think that it would not be a problem if they don't line up perfectly. In house plumbing I think they put a 1/4" drop per foot. Even two 90 degree elbows would not be a problem. I your bus, I would recommend expanding the existing hole in the tank.
I used a grommet, like this one, for going into the plastic tank.

http://www.ebay.com/itm/RV-Dump-Holding-...2c83fc7830


Removing the Microphor toilet also got rid of the 12v compressor, which I removed. That gets rid of the 12v draw when boon docking. I also was able to move the toilet 8" back because there is not the tank on the new toilet, more leg room in the bathroom.

All in all a very good upgrade, downgrading my toilet

[Hotrodhornet]

I agree 100%!!!  It uses almost no water when flushing.
When we stay at the track for a 3 or 4 day race there may be 3 or 4 people taking showers.
The water supply is put to much better use. Plus no worrying about air pressure to flush.
I also removed the 12v compressor, one less thing to maintain. Paul