More Valves than Chernobyl, but you can do the following tricks:

 

 

 

Valve Number

(O=Open, C=Closed)

 

From

To

1

2

3

4

Using Manual Pump

 

Head

Tank

C

O

O

C

 

Head

Overboard

O

C

O

C

 

Head

Pumpout (why?)

C

C

O

C

 

Tank

Overboard

O

C

C

O

 

Tank

Pumpout

C

C

C

O

With shore pumpout

 

Tank

Pumpout station (NOT through manual pump)

C

O

C

C

 

A few notes on the picture:

 

So here are some common questions about my setup:

 

That looks like PVC pipe!?!?

Yup.  Schedule 40 PVC pipe is actually quite flexible and durable and VERY impervious to odor.  Not that my sh*t stinks, of course, but my guests’ might…  Schedule 40 PVC is rated at 200+psi at 70 degrees Fahrenheit, too, is easy to work with, and I have NEVER had a glued joint leak

 

Is that PVC pipe big enough?

The inside diameter of the barbed connectors is just over 1”, as is the inlet and outlet from the pump.  So I decided to use 1” pipe.  Also, 1.5” pipe was sooo big and there really wasn’t room for the valves.  1” costs less, too.  Ask me again in a couple months.  A similar system I set up a couple years ago had 1.5” pipe and I had no problem with it.

 

Why is Valve #4 vertical?

Not enough room between the T and the wall.

 

Why didn’t you use Y valves?

When dealing with sewage, I want to minimize the chances for leakage as much as possible.  I have yet to find a Y-valve that I think will not leak at some time, so I am much more comfortable with a T and a ball valve.  Cost was another factor; 2 Y valves would have run about $80 and all the pipe and parts and valves for thisd setup was about $40. 

 

Are there any other odd features in this system?

The line into the holding tank enters near the top and has a “dip tube” that ends about a half an inch above the bottom so it works for both outflow and inflow.