Holding Tank Deck Pumpout Location

[Mac G]

We are considering adding another waste holding tank and am curious if there is a rhumb-of-thumb or limit on maximum distance between the tank and the deck pump-out fitting. Understanding that shorter would always be better, does it matter if more convenient or practical to run a greater distance?
It seems if all connections are tight and a vacum can be pulled then what is the difference between a longer run inside my boat versus a longer run on land to wherever it is going. But am looking for advice from those experts in these matters so I do not procede based on incorrect or flawed assumptions.
Thank you

 

[Comodave]

I would want the run as short as possible but it probably won’t hurt to have it longer. I would avoid having low spots to hold sewage when not being used. Also I would only use Raritan SaniFlex hose. It is the best hose, period.

 

[porman]

Our boat has two holding tanks and the aft tank has about a 12 foot run. No problem emptying it so far.

 

[O C Diver]

I have seen vertical lifts over over 6'. However, I've been to pumpout stations where my tank would get started with a less than 1' lift (2' to the bottom) and another wouldn't start (because of the initial lift). I would much rather have a long horizontal push from head to holding tank, than a large vertical lift from tank to pumpout fitting.

Ted

 

[Mac G]

Will have to measure up the vertical lift from the new location aft but do not think it would exceed 6 feet. From there am considering going overhead horizontally thru the engine room with rigid 1.5" PVC pipe and then tie into existing pumpout hose from the existing tank (which is located in the engine room) with a Y-valve so can choose which tank to pumpout.
Going overhead would allow the most direct route keeping the pipe out of the way of everything else in there and going with rigid PVC would eliminate low spots and dips.
Could pretty much go with straight pipe and some long sweeps to make the turns to where I need to end up.
That is the concept churning around in my brain but do not want to start until those more expert than me in these matters confirm the idea would indeed work.
I appreciate all the feedback - am new to the trawler world and enjoy learning new stuff every day, so feel free to set me straight if you think I am heading off course with this idea.
Thank you

 

[O C Diver]

It would be helpful to tell us what make, model and length of boat you have.

Personally, I wouldn't tie the pumpout pipe to the existing pumpout port. There's a lot to be said for independent redundancy. The other observation I would offer is to avoid long horizontal runs in the tank discharge. Probably not a good idea to let sludge build up in the pipe.

Ted

 

[SteveK]

Another option would be a transfer pump new tank into the old, remain one pump out location.

 

[grandbanksbayfield]

Limit the vertical. Many pumpout stations do not have enough suction to do a really good job. Horizontal slightly uphill should be okay in most cases.

 

[HeadMistress]

It's the tank VENT line that should be as close to horizontal as possible--shouldn't rise more than 45 degrees and should be as straight as an arrow. Most pumpout fittings are in the side deck above the tank...not necessarily directly above it, so a vertical pumpout line, or one that rises 45 degrees or more, is pretty much unavoidable. Vertical lift limits don't apply to a pumpout line because tank contents aren't being lifte--pushed up by a pump during pumpout, they're pulled out by dockside equipment. As long as the pumpout line is relatively straight--it can have a gentle bend in it if necessary, there should be no problems...but it should NOT go over, up, down and around. That creates problems for even the most powerful pumpout equipment.



--Peggie

 

[Comodave]

Mine is about a 4’ vertical lift and works fine.

 

[Moonfish]

On our Cheoy Lee 46 the pump out fitting is actually on the side of the hull about three feet above the water line. At first I thought it a strange place to put the fitting, as I had only seen them on decks. I was also worried about accidentally dropping the cap in the water (we do have a back up cap in case).

However, I soon found the placement very smart. Firstly, the run from the holding tank (fiberglass integral to the hull) to the fitting was fairly short. Maybe five feet in total. But secondly, if there is ever a "problem" - think of the sh*t hitting the fan sort of problem - we won't end up with a bunch of you-know-what all over the deck. And third, it's one less source of a potential leak source in the deck.

Something to potentially consider. Oh, and in 12 years I have yet to drop the cap in the water...