Holding Tank Location

[Ryan]

My name is Ryan and I’m restoring an 83 year old 48’ raised deck cabin cruiser, The “Edmund G”. I know she’s not a sailboat but I hope to get some help here anyway.
The boat is currently in San Francisco but our plans are to bring her down to Southern California this fall where a holding tank will be required. Back in 1926 they didn’t have holding tanks so I’m forced to find a place for tanks and could use some expert advice.
There isn’t a stitch of plumbing on the boat now so we are designing all new systems including our sewage system.
Our current plan is to put a 53 gallon, low and flat holding tank in the engine compartment between our engines. The tank we are thinking about using is a Ronco Plastics B-312 Witch is 72”L X 15”W X 13”H. The thinking is to keep the tank centered and as low as we can get it.
My questions are:
Do you see any fault with this plan?
Are there any disadvantages to having the tank long and flat?
Is there anything else I should consider before continuing with this plan?

Any advice would be greatly appreciated,
Ryan
edmund-g.com

p.s. I just ordered your book!

Large Diagram
Edmund-G (before restoration)

 

[Don S/V ILLusion]

I'm no expert but can find no fault with what you propose and even one advantage, that being the increased surface area of the tank will promote aeration and therefore help aerobic bacteria do their job more effectively than a typical square tank.

Since than tank imagined is longer along the centerline, any free surface flooding effect should be minimal

 

[Ross]

I would be certain to install it so that the pump-out dip tube is located on the low end of the tank and not install the tank level. One inch of slope should be adequate.

 

[Peggie Hall HeadMistress]

I have a few problems with your plan

I don't have a problem with a flat shallow tank, but I do have a problem with your proposed tank location--it's too deep in the bilge to be able to ise passive ventilation to keep it aerobic ..and also with connecting both toilets to a single tank that appears to be way too far from at least one toilet.

So my answers to your questions are:

"Do you see any fault with this plan?"

Yes.

"Are there any disadvantages to having the tank long and flat?"

No.

"Is there anything else I should consider before continuing with this plan? "

Yup...several things...most of which are addressed in my book. So get back to me after you've read it and I'll be glad to help you sort out the details that'll let you end up with a trouble-free, odor-free system.

Btw...I'm pretty sure the EDMUND G isn't a Trumpy, but she's a great example of that era. What IS she?