Q: black water tank outlet - above or below WL?

vas

vas

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subject line really...

got to drill a 1.5+ inch hole for the black water tank outlet somewhere on around the port cabin...
Was planning to do it above waterline (say 5cm above the a/f line) but some ppl object saying it's going to foul the paintwork et al.
Considering that emptying the tank will be done in the open and I can always speed up and do a few wheel turns either side afterwards I'm pretty sure it's going to clean alright.

Is there any other serious reason to drill below w/l??

cheers

V.
 
Don't know about the specific reasons but ours is above the water line and hasn't fouled anything when emptying.. We usually do a couple of clean flushes afterwards and then pump out again so that might help..
 
sailorman said:
why would you want **** running down your topsides
Click to expand...

I guess because I have already 8 holes below w/l and would be nice not to have more than absolutely needed...
up till now:

anchor wash
toilets (in)
2Xaircon (in-out)
2Xengines
genny
watermaker (in)

cheers

V.
 
sailorman said:
The new Hardy 62 has 17 YES SEVENTEEN above the w/l on the port side alone :rolleyes:
Click to expand...

I'm OK then, with the black water I'm going to have 4 on port side, none on stbrd and 4 on the transom under the bathing platform.

Rafiki, you do have decent access to the seacock in all your boats, right? and I guess there's no need for a swan neck in this case, correct?
A swan neck on a 1.5inch pipe takes some space...

cheers

V.
 
Definitely above the waterline as far as I'm concerned for a number of reasons. First, you avoid having yet another hole in your boat below the waterline. Second, the potential of a syphon effect is reduced and third, you can observe the flow so that you can avoid running the pump dry. The blackwater outlet on my boat is a few inches above the waterline and I can't say that I've noticed a mark on the hull. On most boats, the hull is angled inwards on the side so any flow should not run down the side and any debris should get washed off when the boat moves anyway. The only slight downside is that you create a bit of an obvious slick when you discharge but you're going to be discharging well offshore anyway
 
vas said:
I'm OK then, with the black water I'm going to have 4 on port side, none on stbrd and 4 on the transom under the bathing platform.

Rafiki, you do have decent access to the seacock in all your boats, right? and I guess there's no need for a swan neck in this case, correct?
A swan neck on a 1.5inch pipe takes some space...

cheers

V.
Click to expand...
On the Azi, the Engine and gennie seacocks all easy to access from the Lazerette. Grey water exits above the water line, so no seacock. Black water underneath. Seacock in a hatch in the main cabin floor.
On the Sunline, similar set up, although outdrives so no seacocks for the engines. Black water in the engine bay, grey water above the waterline.
 
You're not going to regret above water outlet... no syphon effect amongst others and as Deleted User points out boat movement will wash hull side anyway .... and less holes to look after below the waterline etc.... Would still fit valves though....
 
thanks guys, happy to have some support for above w/l :D
Alf, mike, would you also have a antisyphon swanneck in the pipe as well as a seacock???
It's getting a bit too much and I have to devise ways to have access to the seacock anyway under the port cabin outer bunk.

cheers

V.
 
Depends a bit on tank placement, pump placement etc... our holding tank is at sea level, pump above top of tank, then fall from pump down to sea level again of approx. 40 Cm ... which means we have a natural fall from the pump and down to sea (swan neck in principle, but not as a distinct swan neck as is with my bilge pumps).
 
hm,

black water tank top is around 40cm below waterline. Pump will be mounted on top of the tank so say pump outlet will be 20cm below w/l. FWIW, pump is a massive diaphragm thing with non return valves fitted. So looks like a swan neck will be needed, have to find a decent place to fit all that mess and still have access to the seacock...

V.
 
Nor sure where you plan to place the tank.... Have you considered pipes running backwards into Engine Room, placing pump in there (if not too far...) ... and in there you will have plenty of space to run swan neck and have access to valve?
 
vas said:
thanks guys, happy to have some support for above w/l :D
Alf, mike, would you also have a antisyphon swanneck in the pipe as well as a seacock???
It's getting a bit too much and I have to devise ways to have access to the seacock anyway under the port cabin outer bunk.
Click to expand...
The blackwater tank on my boat is below the waterline so in my case I definitely thought an antisyphon loop was necessary and so did the yard that installed it. I also thought it was a good idea to fit a seacock. Even though the outlet is above the waterline, it dips below the waterline when the boat rolls.
FWIW every other Ferretti I've seen has it's blackwater outlet above the waterline
 
Alf,

placed the tank (which is rather long 108lt) under the inner bunk of the port cabin. So effectively just above the keel and slightly offset to port.
Tanks are just behind the bulkhead aft.
So routing a pipe to the e/r means I got to lower the pipe to keel level, drill a hole on the bulkhead, go under the tanks and then do the route to either port or stbrd. Indeed plenty of space there.
However, the dip under the tanks means that I potentially have a piece of pipe full of **** 24/7 which is not particularly exciting...
In theory the diaphragm pump should be able to push/clear the pipe completely but not too sure.
No option to put the blackwater tank on the e/r - can physically do it, but not so keen on hard **** to chisel out of that due to the e/r temps not to mention that pipe runs form the heads will be in excess of 4m!


So alternatively, got to route the pipe to the outer bunk of the same cabin, fit the seacock under the bed with access from the fix open shelf under the bed and be done with it.
Got to measure and test access to seacock though and may have to fit an elbow to be able to do the swan neck between the iroco frames without messing up and wasting lots of space.

will check tomorrow and report.

cheers

V.
 
Deleted User said:
The blackwater tank on my boat is below the waterline so in my case I definitely thought an antisyphon loop was necessary and so did the yard that installed it. I also thought it was a good idea to fit a seacock. Even though the outlet is above the waterline, it dips below the waterline when the boat rolls.
FWIW every other Ferretti I've seen has it's blackwater outlet above the waterline
Click to expand...

thanks mike,

better safe than sorry, so seacock and swan neck to fit. will take a few pics of the setup and post tomorrow

cheers

V.
 
Divemaster1 said:
Nor sure where you plan to place the tank.... Have you considered pipes running backwards into Engine Room, placing pump in there (if not too far...) ... and in there you will have plenty of space to run swan neck and have access to valve?
Click to expand...
Yup thats what I did in part. There was no space for an outlet with an antisyphon loop where we initially wanted to put it so the yard ran the pipe back into the engine room where there was plenty of space for the loop. Vas, don't forget also that you need a vent pipe from the tank but the outlet can be well above the waterline. Small tip; put the vent pipe outlet as far away from any cabin window as you can otherwise every time you flush a toilet, you will get a whiff of pungent air wafting through any open window nearby. You can reduce this with a filter but then you need to replace the element regularly
 
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