fisherman
Well-Known Member
I would suggest inertia: you have to set the whole column of water in motion.
Why not wash up in a colander, so no bits down the drain?
Why not wash up in a colander, so no bits down the drain?
Sea Cock Advice
- Thread starter Little Dorrit
- Start date
Tranona
Well-Known Member
pvb has already explained it. The deeper the drain the greater the pressure of the water left in the section of the pipe under water in relation to the head above so the longer it takes to displace the water underneath by overcoming the pressure.
Just make a rig to replicate the run of pipe and the depth of water and prove it for yourself.
pvb
Well-Known Member
Actually, my explanation didn't support your statement that "The deeper the exit under water the slower the drain." Regardless of the position of the seacock, the only thing which affects the flow is the head between the sink and the waterline. You could argue that a seacock deep down would involve a greater length of pipe which would introduce a bit more friction, but it's clutching at straws.
lpdsn
Well-Known Member
That's an interesting theory. Do you think there'll come a point where the outboard end is so deep the flow will reverse?
Length of the pipe of course will be a factor in the flow rate. See Poisieuille.
rogerthebodger
Well-Known Member
That's why I asked the question as I agree with you. With a constant distance between the sink outlet and the waterline which will be constant on a stable boat will give a constant flow> This flow will only depend and what friction is in the system, valves ,elbows, reducers and pipe length and pipe diameters. This is constant for a particular setup.
I also did fluid dynamics a university many years ago.
The one think that need to be considered with a seacock outlet above the waterline is the lack of head between the sink and the outlet height. This will be less thet the head when the sea cock outlet is below the waterline. Once this becomes the design the best setup I found was to have the outlet to sea directly below the sink outlet . This gives the least friction possible as no elbows and only the seacocl valve below the waterling close to the hull.
pvb
Well-Known Member
Most above-waterline outlets are in fact very close to the waterline and there'll be minimal difference - indeed the tiny reduction in head would most probably be outweighed by the shorter pipe with less friction.
rogerthebodger
Well-Known Member
In my case the length of the pipe to the outlet just above the waterline as you say was longer and had elbows that increased the friction which was eliminated with a direct down pipe and no elbows.
The sinks I had problems with were close to the center line so shorter to bilge that to side.
Heckler
Well-Known Member
Just use the simple rule of thumb as used by generations of oil field workers, 27" height of water equals one psi. So measure the top of the water level in the sink to the waterline and that will give a good idea of the psi pressure.
Stu
pvb
Well-Known Member
I'm not sure how that would give any better idea of the effectiveness of the plumbing.
2Tizwoz
Well-Known Member
As the outlet is submerged an airlock forms until the height of water in the basin is greater than the height of water in the discharge pipework connected to the outlet.
The air is trapped in the pipe from the basin and cannot escape to permit the water from the basin to enter the pipe. It must gurgle as the air slowly escapes. Until H1 is greater than H2 there will be no flow.
An alternative solution would be to connect a second pipe from half way down the discharge pipe from the basin to an overflow on the side of the sink. That pipe could be relatively small as it would only be carrying a small flow of air.
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pvb
Well-Known Member
ghostlymoron
Well-Known Member
I thought it was 'nowt so queer as folk' or isn't that allowed now?
pvb
Well-Known Member
ghostlymoron
Well-Known Member
It isn't.Why is your username greyed out?
