Has anyone had this

peteandthira

peteandthira

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little problem with their sink?

Our "bathroom" sink takes AGES to drain away. However, if I just give it a slight poke with a standard rubber plunger, woosh away goes all the water. I am literally only just touching the plunger over the sink hole and then removing it.

I assume from the resulting easy drain away that the pipe does not have a blockage. As soon as the rush of water has gone, then filling it up again reverts back to the really slow drainage.

Has anyone else seen this or know where the problem is?

Ta

Pops
 
Yes It seems to be the basis of Archimedes principle if the water is added solwly it drains slowly presumably because of friction in the pipe,,laminar flow etc etc.
If I turn off the seacock and open it again the water rushes out, presumably because of the acceleration- strange but true and repeatable.

Easy to demonstrate with a sink full of water where I would have thought the "head" of water was sufficient to force it out.

curious
 
Sounds like a blockage that is floating in the pipe.

once the presure comes off it floats and allows the water to flow but with the weight of water on it, it will block. This is how a tyre valve works.

We often came accross roof problems that were caused by tennis balls that only blocked outlets when there was torrential rain.

Close the seacock, take off the pipe and have a look.

tony.
 
You could try using the inflatable dinghy pump to 'blow' down the pipework,more effective and more prolonged than a plunger.
Plan B,renew the pipe,it may be old and kinked and partially blocked along its entire length.
 
Thank you all for your ideas above. The pipe is only 2 years old, as is the boat, and it has always done it. I guess the only solution is to take it out and examine it, although that will involve a massive faff.

Ah well, another afternoon spoken for!

Regards

Pops
 
We once had something like this on a traditional 100' schooner. In the galley it had a drain in the floor to make cleaning more easy - but the outflow was very week...

So the two clever ships engineers decided to fix it with pressurized air. They closed the seacock, took off the hose at the seacock and applied pressurized air - the result was a very angry cook whose apron was spotted with black marks and the two engineers crawling around the galley for two hours cleaning everything including the ceiling..... :-) But the blocking was a thing of the past...

So be carefull whatever measures you take....
 
I have the same problem, but I only have to put my finger in the plug hole and pull it out and the sink draind immeditely. My drain only has a couple of feet before it reaches the seacock. So I can only think that it is 'surface retention' versus 'the small diameter of the drain hose' versus the 'vertical drop of the drain hose' to the waterline that causes it.

A minor irriration!
 
We've got the same problem on our galley sink - it's been like this since new (a year ago). I'm convinced its an air lock problem but never got to the bottom of it. You'd expect a sink full of water would drain easily, but it only goes down with a quick flip of the stop cock or hand over the plug hole.

Let me know when you find a solution

Dr Bob
 
I think IanR has the right idea. If there is air in the pipe then the whole internal diameter is not draining the water ie the water is spinning around the edges (or thereabouts). If you induce a ram effect with your plunger, you are creating a 'solid' lump of water across the full diameter of the drain. The weight of this water then sucks more water down the pipe. Similar really to a siphon but you don't have a section above the inital drain hole or it would never empty on its own. It's probably a section that is a bit horizontal at one point.

A further thought is that as you are only lightly touching the drain with the plunger, you may be sucking a small column of seawater up the pipe as you remove the plunger. This column of seawater then acts as the downforce as it falls back to get the drain flowing.
 
We have the same with our kitchen sink, which exits below waterline, although I dont know whether or not that is significant. It has happened for the 6 years we have had the boat. The sea cock has been replaced during that time. The hose fall is almost vertical.

Please let me know when you resolve yours.

Ian
 
It could be your friendly shell fish in the seacock. It lives normally with its shell open blocking the pipe mostly and feeding off the water passing. Then you bounce the water with the plunger and they close up rapidly. Once it is all quiet back he goes to eating. Ours always have someone living in them when we pull the boat out.
 
Try this one, fill a milk bottle with water, invert it and time how long to empty. Repeat, but this time give the bottle a clockwise ‘swirl’, the water runs out much slower, with an air ‘cyclone’ in the middle.

Not sure about Archimedes, but even with a straight exit pipe the water does like to cling to the inner edge, leaving air down the centre, as per the milk bottle trick above. I think this is due to the small bore of boat, sink outlet pipes and seems to be a very common problem.
 
isandell

Well, by the sound of your setup, it must be the will of allah or somebody! I wouldn't have thought that any superior physics nollege can sort that!

Glad to hear that it's not just mine!

Pops
 
Got the same problem with my drain in the sink. It drains out below the water line. All I have to do is put the plug in the hole and lift it out with a "Pop" and the water goes out fine. I've put it down to the back pressure on the outlet from outside. I know the physics don't add up but it seems to be the cause of the problem, 'cause when I'm on the hard and put water down the sink it goes down straight away with no problem. Does yours drain above or below the water line, might be the answer.
Greeny
 
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