 |
|
03-02-2016, 22:35
|
#1
|
Registered User
Join Date: Aug 2015
Location: Sozopol
Boat: Riva 48
Posts: 1,409
|
Holding tank discharge via thru-deck opening
I am thinking of removing the thru-hull discharge of my holding tank and pumping out my holding tank only thru-deck (either by vacuum at pump-out stations or by means of a Whale pump). In the latter case, I would need to attach a short hose in the deck opening to divert the waste over the starboard side.
On my Hunter 31 the waste from the toilet goes directly to the holding tank. The holding tank discharge hose goes to a Y-valve, one end goes to the thru-deck pumpout port, the other goes through a Whale pump, a siphon, and then to the thru-hull valve. My thru-hull valve is broken in the closed position (unlikely to repair it soon) and the space for hoses from the tank under the V-berth to the toilet is very limited. It was a pain to remove the three hoses and it would be a bigger pain to push three new hoses and do the siphon.
I am thinking of connecting the two output hoses from the Y-valve with a T-connector (one goes through the Whale pump, the other straight to to T-connector) then having a single hose going to the thru-deck opening. When I want to empty the holding tank manually (not often), I would divert the flow through the Whale pump and then insert a short hose/fitting in the thru-deck opening (from the deck) that will lead the waste over the starboard side to the water. It will not be a pretty sight but will do. In this way, I can eliminate the thru-deck valve and siphon completely and have a much simpler system.
I have two concerns: 1) can the vacuum pump-out damage my Whale pump and 2) will the Whale pump have enough power to push the liquid up to the deck opening (about 2.5 feet vertical distance, 5 feet horizontal distance)? What do you think?
|
|
|
04-02-2016, 08:19
|
#2
|
Marine Service Provider
Join Date: Feb 2011
Posts: 3,123
|
Re: Holding tank discharge via thru-deck opening
1) can the vacuum pump-out damage my Whale pump?
Yes, it could. What you want to do would also make the pump a blockage in the pumpout line that would interfere, if not prevent entirely, a pumpout from pulling anything out of the tank.
2) will the Whale pump have enough power to push the liquid up to the deck opening (about 2.5 feet vertical distance, 5 feet horizontal distance)?
Check the owners manual for your model for those specs. Even if it can, the pump will still be a blockage in the pumpout line.
There is a third consideration: Even if you come up with a way to rinse it out, you're gonna have about 5' or more of drippy hose that's still likely to be smelly to store aboard. Depending on the wind and other factors, you're also likely to have a stained hull after dumping.
So all things considered, this is NOT a great idea. Bite the bullet and repair--or replace if necessary--the seacock.
__________________
© 2025 Peggie Hall
Specializing in marine sanitation since '87.
Author: "NEW Get Rid of Boat Odors"
|
|
|
04-02-2016, 09:16
|
#3
|
Registered User
Join Date: Apr 2007
Location: Marina del Rey, California
Boat: President 43 Sportfish
Posts: 4,105
|
Re: Holding tank discharge via thru-deck opening
Quote:
Originally Posted by Pizzazz
... I would need to attach a short hose in the deck opening to divert the waste over the starboard side...
|
Don't be "that guy."
__________________
1st rule of yachting: When a collision is unavoidable, aim for something cheap.
"whatever spare parts you bring, you'll never need"--goboatingnow
"Id rather drown than have computers take over my life."--d design
|
|
|
04-02-2016, 09:53
|
#5
|
Registered User
Join Date: Aug 2006
Location: Skagit City, WA
Posts: 25,765
|
Re: Holding tank discharge via thru-deck opening
Fix your seacock
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard
|
|
|
04-02-2016, 09:56
|
#6
|
Registered User
Join Date: Apr 2007
Location: Marina del Rey, California
Boat: President 43 Sportfish
Posts: 4,105
|
Re: Holding tank discharge via thru-deck opening
Quote:
Originally Posted by Tetepare
|
Corruption in city hall and in the water.
__________________
1st rule of yachting: When a collision is unavoidable, aim for something cheap.
"whatever spare parts you bring, you'll never need"--goboatingnow
"Id rather drown than have computers take over my life."--d design
|
|
|
04-02-2016, 10:43
|
#7
|
Registered User
Join Date: Jun 2008
Location: Tampa, FL
Posts: 5,032
|
Re: Holding tank discharge via thru-deck opening
Quote:
Originally Posted by peghall
So all things considered, this is NOT a great idea. Bite the bullet and repair--or replace if necessary--the seacock.
|
I think you're being too kind. This a BAD idea!
|
|
|
05-02-2016, 08:26
|
#8
|
Registered User

Join Date: May 2011
Location: Miami Florida
Boat: Ellis Flybridge 28
Posts: 4,078
|
Re: Holding tank discharge via thru-deck opening
If you have a ball valve screwed to a thru-hull, it's easy to change the valve while the boat is in the water. You can plug the thru-hull from outside the boat or use a Seabung to do it without going over the side.
Seabung Breach Control
Seabung
__________________
Retired from Hopkins-Carter Marine Supplies
|
|
|
05-02-2016, 08:54
|
#9
|
Registered User
Join Date: Mar 2010
Location: Annapolis MD
Boat: Building a Max Cruise 44 hybrid electric cat
Posts: 3,286
|
Re: Holding tank discharge via thru-deck opening
We carried a spare manual bilge pump connected to a banjo fitting that could be used on deck to empty the holding tank offshore. We would only use this when leaving (outside) a country that didn't allow direct discharge (ie leaving US for Bahamas). Once you leave the US with a half full holding tank, it's difficult to find a pumpout in the next country... You'll need a way to empty the tank.
I bought the banjo fittings from Mcmaster-carr to connect to the standard on deck fitting. There was then about two feet of 1.5" hose, the manual bilge pump and then another few feet of 1.5" to run overboard. After use, all would be disinfected and put in a Rubbermaid container in the bilge storage. We only had to use it in a few areas, but saved travelling for months with a holding tank of old waste.
The typical option is to have a 3-way valve mounted below deck, but I didn't want the permanent hose run, as we didn't have the room for it in the holding tank/head area.
Matt
edit: reread the OPs post. Fix the seacock!
|
|
|
05-02-2016, 09:24
|
#10
|
Registered User
Join Date: Feb 2011
Posts: 2,150
|
Re: Holding tank discharge via thru-deck opening
Oh yuck. Deep dodo all over the deck, in the cockpit, and even perhaps down below. A hull mount opening way cleaner and easier to wipe down when the inevitable happens, and it will. Saw a yacht getting sucked out when the system "burped" due to an air lock. Covered that boat with a lot of flying, well you know what.
|
|
|
05-02-2016, 09:57
|
#11
|
Registered User
Join Date: Feb 2013
Location: Cruising Mexico
Boat: Norseman 400
Posts: 435
|
Re: Holding tank discharge via thru-deck opening
Thinking down the road, making a change this significant will likely make it more difficult to sell the boat when the time comes.
We replaced a total of 37' of sanitation hose on our Norseman 400. Not that bad of a job really and very much worth the effort. The Trident brand was a bit stiff to work with but slid into place nicely and completely contains any odor.
|
|
|
05-02-2016, 10:09
|
#12
|
Registered User
Join Date: Feb 2013
Location: Ocala FL
Boat: 1979 Bristol 35.5 CB
Posts: 1,984
|
Re: Holding tank discharge via thru-deck opening
Ever see the movie "Christmas Vacation", Cousin Eddy with a hose at the curb...
very appealing
__________________
John Churchill Ocala, FL
NURDLE, 1979 Bristol 35.5 CB
Currently hauled out ashore Summerfield FL for refit
|
|
|
05-02-2016, 12:50
|
#13
|
Registered User
Join Date: Jun 2010
Location: Townsville, Australia
Boat: Oceanic 46
Posts: 23
|
Re: Holding tank discharge via thru-deck opening
Thru-hull fitting much easier and cleaner to use.
|
|
|
05-02-2016, 13:01
|
#14
|
Registered User
Join Date: Aug 2006
Location: Skagit City, WA
Posts: 25,765
|
Re: Holding tank discharge via thru-deck opening
Unless you repair as you should, why change anything? Leave the thru hull shut, same as your mods right?
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard
|
|
|
05-02-2016, 13:05
|
#15
|
Registered User
Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 9,764
|
Re: Holding tank discharge via thru-deck opening
If this was such a good idea, more boats would have it.
They don't make 'em the way they do for the convenience of the builders alone, let alone the owners.
Mostly, they do it because it's been proven to WORK.
Fix the seacock. I had the same leaking seacock, I replaced it. I actually had the yard do it, one of the few times I EVER let anyone else work on my boat. It was worth the $200. WELL worth it.
The other two times: standing rigging replacement and a macerator pump.
Seeing the pattern here?
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Mill Bay, BC, SR/FK, M25, Rocna 10 (22#) (NZ model)
|
|
|
 |
|
Thread Tools |
Search this Thread |
|
|
Display Modes |
Rate This Thread |
Linear Mode
|
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
|
Advertise Here
Recent Discussions |
|
|
|
|
|
|
|
|
|
|
|
|
Vendor Spotlight |
|
|