inline breather for 1" Sink Drain

On my old galley sink, what I thought was just a mash up of various crossovers to get between the sink outlet and hose diameter, turned out to be a non return valve. The valve was quite dirty and caused slow drainage. I removed it and now the waste water flows out quite easily. If you have a steel bushing that crossovers from sink waste diameter with a smaller nipple to waste hose diameter you may find that there is a valve inside.

The reason that it was there is that the sink back fills via the waste pipe when well healed, however serviced seacocks now prevent that.
 
BlowingOldBoots said:
The reason that it was there is that the sink back fills via the waste pipe when well healed, however serviced seacocks now prevent that.
Click to expand...

Older boats like mine with low freeboard can have slow sink drainage due to lack of head, as well as backfilling issues.
A waste pump helps greatly with both. less/no need to remember to shut the sea-cock.
I'd expect a NRV in the sink-drain to give constant trouble.
 
If your outlet is below the waterline it will always be slow to drain because of the head of water in the lower part of the pipe. Only solution is to take the outlet up to the waterline as it is on many modern boats.
 
Tranona said:
If your outlet is below the waterline it will always be slow to drain because of the head of water in the lower part of the pipe. Only solution is to take the outlet up to the waterline as it is on many modern boats.
Click to expand...

Oh, dear! Lifting the outlet above the waterline (if it is indeed below the water) will just make it worse. A smart Frenchman called Pascal did work on equilibrium and is immortalised with "Pascal's Tubes".
 
paella said:
Is there any way of solving the slow or no drainage problem I'm having with my sink?
Click to expand...

Depends what the cause of the problem is.

First step obviously is to check whether the hose is kinked or crushed anywhere. Mine had been folded too tightly to fit into the space behind the drawers, and was squashed nearly shut. Water poured down one sink spouted straight up into the other, and only a dribble of it actually went out of the boat. Changing it to a nice smooth run with one necessary elbow and a Y-joint meant that it now drains rapidly and the drying dishes in one sink don't get splashed with the dirty water being emptied.

Pete
 
Tranona said:
If your outlet is below the waterline it will always be slow to drain because of the head of water in the lower part of the pipe. Only solution is to take the outlet up to the waterline as it is on many modern boats.
Click to expand...
It's a Vancouver 27...you could be right I'll have a look.
 
earlybird said:
Older boats like mine with low freeboard can have slow sink drainage due to lack of head, as well as backfilling issues.
A waste pump helps greatly with both. less/no need to remember to shut the sea-cock.
I'd expect a NRV in the sink-drain to give constant trouble.
Click to expand...
I'd expect the two valves in a waste water pump to be twice as much trouble!

The best answer may be to not be in too much hurry or not to squander so much water when washing up?

More usefully, a full bore strainght through seacock enables cleaning the drain hose with a length of stiff garden wire spun in a cordless drill.
Or pour a bit of bleach down it several times a week.
 
lw395 said:
I'd expect the two valves in a waste water pump to be twice as much trouble!
Click to expand...

The difference is that with a single non-return valve you're relying on just the head of water (which is generally pretty small, or you wouldn't want the valve) to operate it. With a pump, you're applying external force to push everything through.

We had a pumped-out sink on our previous boat and, apart from being a little less convenient than just pulling a plug, it worked perfectly well.

Pete
 
A frequent cause of this on my boat is hot, greasy washing up water congealing when it hits the cold seawater.
We periodically close the seacock and dose the pipe with soda crystals and hot water. This helps temporarily, in bad cases use the dinghy pump, but watch out for blowback, yuck!
 
awol said:
Obviously Pascal's efforts were wasted! Despite Tranona's undoubted taste in yachts, his assertion that lifting the outlet will improve flow is sadly flawed.
Click to expand...

While you are in the bath tonight, take with you 1m of 25mm plastic tube. Submerge the bottom 25cm in your bath water. Fill the tube, preferably with coloured water. Not how slowly the level of the yellow water falls as it is achieving equilibrium by pushing against the 25cm head of water.

You have now replicated the OPs problem.

Now lift the tube out of the bath water and note how quickly the remaining water runs out.

You have now solved the Ops problem. Raise the outlet above the waterline - or more likely just on the waterline and the only constraint to draining will be the diameter of the hose and the head of water in the sink.
 
Tranona said:
While you are in the bath tonight, take with you 1m of 25mm plastic tube. Submerge the bottom 25cm in your bath water. Fill the tube, preferably with coloured water. Not how slowly the level of the yellow water falls as it is achieving equilibrium by pushing against the 25cm head of water.

You have now replicated the OPs problem.

Now lift the tube out of the bath water and note how quickly the remaining water runs out.

You have now solved the Ops problem. Raise the outlet above the waterline - or more likely just on the waterline and the only constraint to draining will be the diameter of the hose and the head of water in the sink.
Click to expand...

The head of water does not change, because the sink remains at the same height.
(actually if the outlet is to one side, the fall in the hose will be less on one tack.).
There is a bit less viscous resistance from the water at the end of the hose.
At the price of a greasy stain from the drain to the waterline.
And on most boats, a longer hose. Which means more drag, particularly if the hose is not straight.
 
I find it unlikely that low head of water should be the reason for the OP's problem.
In my boat the sink drains straight down through a hose to a 1" under water valve + skin fitting, about 600mm in total. The static water level is maybe 150mm below the sink outlet.
Have never had any problems with slow drainage.
However the hose ID is 32mm, which might speed things up a bit.
 
Is the hose a straight vertical drop ? I have a clear pipe and the same problem. I can see an air bubble which prevents quick drainage. Once this is moved the sink drains fast. Winter job is to lengthen then hose and make an S bend to remove the air lock.
 
lw395 said:
The head of water does not change, because the sink remains at the same height.
(actually if the outlet is to one side, the fall in the hose will be less on one tack.).
There is a bit less viscous resistance from the water at the end of the hose.
At the price of a greasy stain from the drain to the waterline.
And on most boats, a longer hose. Which means more drag, particularly if the hose is not straight.
Click to expand...

It is the head of water outside the boat that causes the slow draining. achieving equilibrium is not instantaneous as the water from the sink does not go through the water in the pipe but pushes it out.

Do the bath test.
 
Not sure what your point is. Hydraulically, the flow rate is determined by the upstream and downstream levels. If the outlet is submerged, the effective level is the seawater level not the level of the outlet so raising the skin fitting won't help unless you also raise the sink. All you can do is make sure the pipe is clean and not restricted, fit a bigger pipe or fit a pump. Slow emptying is not usually a problem.
Tranona said:
While you are in the bath tonight, take with you 1m of 25mm plastic tube. Submerge the bottom 25cm in your bath water. Fill the tube, preferably with coloured water. Not how slowly the level of the yellow water falls as it is achieving equilibrium by pushing against the 25cm head of water.

You have now replicated the OPs problem.

Now lift the tube out of the bath water and note how quickly the remaining water runs out.

You have now solved the Ops problem. Raise the outlet above the waterline - or more likely just on the waterline and the only constraint to draining will be the diameter of the hose and the head of water in the sink.
Click to expand...
 
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