sink drain is below the water line

[bowman316]

I have a 26 ft sailboat, and the sink in the galley drains straight down, thru the hull, and the fitting is below the waterline. But the sink is above the water line.

So would sea water come in thru the fitting, up to the waterline? and anytime i add water to the drain, that will push sea water out to make the water level in the pipe even again with the sea level?

imagine a straw half way under water.

the boat is not in the water yet, so i just want to make sure i don't need any new thru hull fittings before i launch it.

also, the head intake and output are below the waterline too. is all of the standard practice, to put them all below the waterline?

 

[Summer Fun]

Re: sink drain is below the water line

I don't own a sail boat. But that doesn't seem right ??
My sink drain is about 1ft above the water line.

 

[Home Cookin']

Re: sink drain is below the water line

I doubt the head is legal.
I wouldn't think the sink would drain well, except when you are underway. but if it drained above the line it would leave a stain.
through-hulls beliow the water line scare me.

 

[bowman316]

Re: sink drain is below the water line

yea, the head is a direct discharge, and not legal.
the boat is a 1970, and it was legal back then.
All i have to do is put in a holding tank.

 

[bowman316]

Re: sink drain is below the water line

I just did a small scale test, with a styrafoam cup and a straw.
I put the straw thru the bottom, and cut the straw so that the top ened half way up the cup.

I put the cup half way into the water, and as long as the top of the straw was above the water line. get the straw below the waterline, and water came up thru the straw.

So as long as the sink is above the waterline, then it will not come up thru the pipe.

i also added water into the top of the straw, and the water drained right out. It instantly equalized with the level of the water outside.

 

[bhammer]

Re: sink drain is below the water line

Think about our glass of water at the resturant. Water never rushes out the top of the straw and once you finish sucking, the water falls back down the straw to the same level as the water.....

Just hope that the line does not break or leak at the hull fitting.

 

[bowman316]

Re: sink drain is below the water line

there is a shutoff valve right at the fitting. so nothing could break that is LOWER than the shutoff.

every fitting on this boat has a shutoff built into the fitting.

 

[kenmyfam]

Re: sink drain is below the water line

I would be keeping it shut off till I needed the drain then shutting it off again afterward.

 

[bones774]

Re: sink drain is below the water line

there is a shutoff valve right at the fitting. so nothing could break that is LOWER than the shutoff.

every fitting on this boat has a shutoff built into the fitting.

Except the shutoff valve itself or the thru hull fitting. Gate valves are notoriously susceptible internal breakage in boating environments. If you really wanna check insert a screwdriver from outside the hull into the thruhull and wiggle some, see if the plastic breaks,cracks and see if you could put ball valves on all fittings.

 

[bhammer]

Re: sink drain is below the water line

there is a shutoff valve right at the fitting. so nothing could break that is LOWER than the shutoff.

every fitting on this boat has a shutoff built into the fitting.

I wouldn't count on that! A guy at our dock had his boat half sink because the seal between the hull and the fitting finally gave out. It only half sank because he has a water bug in the boat that paged/texted him at 2 in the morning and it wasn't fully leaking at a fast rate. But, faster than his two bilge pumps could work. Was about 2" from the closest point of a full on flood. He had to bail the boat with an ice bucket until a buddy came with an engine powered pump. That morning, the marina was nice enough to let him borrow floats to get it out of the water.

 

[backwater dawg]

Re: sink drain is below the water line

I would be keeping it shut off till I needed the drain then shutting it off again afterward.

I would junk the blowboat and buy something with 2 keys

 

[bowman316]

Re: sink drain is below the water line

2 keys?

 

[Summer Fun]

Re: sink drain is below the water line

I think he's saying ?? Buy a boat with twin motors.

 

[bowman316]

Re: sink drain is below the water line

the thing is that i want unlimited range.
and not have to fuel up every 100 miles or so

 

[Z71Man]

Re: sink drain is below the water line

My 1982 Catalina 25 has 2 sinks that both drain below the waterline. Hasn't sunk yet.... I usually use only 1 sink as intended and I keep that valve open. The other sink is a repository for cell phones, wallets, etc, as anyone with a sailboat will understand, and that valve stays shut.... I still find it absolutely hilarious that anyone ever found it necessary to put 2 sinks in a 25 foot boat. Proof positive that boat shows have not benefited recreational boating in the slightest!

 

[Ned L]

Re: sink drain is below the water line

Absolutely nothing unusual or wrong with the setup you have. (Though as has been pointed out, a sink drain above the waterline does add a bit of 'security' if something fails.) The inlet & outlet for the head are always below the waterline.