Size of through hull for sink?

[SvenH]

I am moving my boats kitchen sink to a new location, requiring an new through hole fitting.

What size of through hole/ball valve should I use?
Smaller would be cheaper and maybe safer, bigger would allow bigger chunks of food through when washing dishes.

Do any of you have experience in using a small size?

 

[Poignard]

Mine is the same diameter as the sink outlet, 3/4".

 

[Minerva]

Ours is about 25mm or so. The most important consideration is to mount the through hull at the waterline so it’s easy to stick a drain snake up to unclog every so often.

 

[BabaYaga]

Mine is also 25mm/1". The hose is drawn vertically, almost in a straight line, to the ball valve/through hull, positioned a fait bit below the water line.
Never had a clogging in 40 years.

 

[geem]

Ours is 1.5 inch. Our sink is a domestic double sink from a house. Small children have been known to disappear down the plug hole?

 

[Lightwave395]

Mine is 3/4", it might be a stupid question but I'd like an explanation as to why water drains out of the sink instantly if the boat is out of the water but takes forever if it isn't

 

[Plum]

I am moving my boats kitchen sink to a new location, requiring an new through hole fitting.

What size of through hole/ball valve should I use?
Smaller would be cheaper and maybe safer, bigger would allow bigger chunks of food through when washing dishes.

Do any of you have experience in using a small size?

19mm bore minimum 25mm is better and ideally a continuous downwards flow from sink to skin fitting.

Www.solocoastalsailing.co.uk

 

[eilerts]

Mine is 3/4", it might be a stupid question but I'd like an explanation as to why water drains out of the sink instantly if the boat is out of the water but takes forever if it isn't

No, it is a rather good question, that deserves its own thread.
My sink drain is 1"

 

[KevinV]

Mine is 3/4", it might be a stupid question but I'd like an explanation as to why water drains out of the sink instantly if the boat is out of the water but takes forever if it isn't

Because the through hull is "x" cm below the waterline, meaning there is "x" cm of water to get moving. The sink water will fall on top of this and have to get the whole column of water moving. Once moving it is still only imparting a smaller amount of kinetic energy to the column of water than if the pipe were empty to start with

 

[Poignard]

Good if you can get it to drain by gravity but on my boat the sink is just above waterline level so it has to be pumped out.

 

[Whaup367]

Previous boat (32' late-70s racer/cruiser) had a pretty small sink drain (near vertically) to correspondingly small through hull- maybe just 15mm- The sink could be plugged with a cork and was a pain because it blocked very easily; though I don't recall the actual pipe getting bunged up.
Current boat (36' 90s Cruiser) has a bigger setup- with a standard looking plughole and, I think, a 32mm through-hull. Drains near vertically and is problem-free.
I'd favour the latter in a cruising boat. I don't know if larger through hulls add significant drag?

 

[alan_d]

Having blocked my sink more than once with the residue from the rice pan, I now tip this directly overboard from the cockpit, but I feel irrationally guilty for doing so. Do I need therapy?

 

[vic008]

Mine has the swan neck(?) And jams often. Any reason why shouldn't ditch for a straight line?

 

[john_morris_uk]

Mine has the swan neck(?) And jams often. Any reason why shouldn't ditch for a straight line?

None as far as I can see. The swan water trap is to stop the smell from the drain in a domestic installation getting into the house. It serves no useful purpose on a boat. I’ve never seen one fitted.

 

[andsarkit]

Good if you can get it to drain by gravity but on my boat the sink is just above waterline level so it has to be pumped out.

Mine is only just above the waterline but if I am sailing heeled over with the rail awash, the water will backfill the sink and start to overflow. I now always remember to shut the seacock when sailing.

 

[Daydream believer]

What annoys me is the HM taking his RIB past at speed & the wash raising the water level outside such that it causes the air space between water level & sink plug to reduce. It happens when one is not looking. It craftily blows the plug out of the sink hole & lets the hot water complete with Fairy Liquid escape so I am left with nothing to wash the dishes with. I then have to refill the sink.
I now find that the solution ( other than pay said HM quickly so he keeps away) is to let some water into the waste pipe & whilst it is draining put the plug in the hole. This creates a negative pressure to counteract the positive pressure of that darned HM & his RIB.
So the point of this rant is that if the OP has a smaller diameter pipe it is easier to create the neg pressure because the water drains away more slowly. If he has a large diam pipe it would be almost impossible to back the water up enough before getting the plug in the hole
And YES I have turned up my own plastic plug to get a tighter fit. That just means that it pops up higher when it does blow off. Bloody HM & his RIB. Should slow down like he tells everyone else to

 

[john_morris_uk]

Or use a bowl in the sink?

 

[Poignard]

Mine is only just above the waterline but if I am sailing heeled over with the rail awash, the water will backfill the sink and start to overflow. I now always remember to shut the seacock when sailing.

Mine doesn't do that because the drain pump acts as a non-return valve, and is above the waterline anyway.

 

[Daydream believer]

Or use a bowl in the sink?

More junk & would not fit. Plus I would have to keep moving it to have a pee when under way
You have to think these things through

 

[john_morris_uk]

More junk & would not fit. Plus I would have to keep moving it to have a pee when under way
You have to think these things through

Mrs M says she’s never sailing with you because:
Either
She might be offered refreshments from something washed in your toilet (sink).
Or
You’ve got a disturbingly warped sense of humour.

PS small bowls are readily available. They’re very handy for all sorts of things. Including used as a tray to carry hot drinks around in.