What is this sink drain part?

[DoubleD]

The attached photos are of the underside of my head sink. Of course it’s the sink drain, but I’ve never seen such an apparatus. Other than to direct water to the overboard drain hose, what other function does it provide? Is it some sort of back-flow device? The drain thru hull is above the waterline. The second photo of the underside appears to be a thumb screw embedded in some sealant. Seems like some sort of jerry-rig repair.

Thanks,
DD

[replusted]

It looks like an air gap.

[Bowdrie]

I think it's a "capture bowl", so to speak.
Drop your wedding ring down the drain to see if I'm right.

[DoubleD]

Originally Posted by Bowdrie

I think it's a "capture bowl", so to speak.
Drop your wedding ring down the drain to see if I'm right.

So the bowl at the bottom would likely always have water in it, like a shower sump that gets swampy. Maybe that is why someone fashioned a drain hole in the bottom. A dirt dwelling house has P-traps, but I understand that is more to prevent sewer gas to come up through the sink drain. Searching the online marine suppliers, I've not seen anything similar.


thanks,
DD

[Calif.Ted]

I used to do some camper and van conversions Long, Long ago, and that was a common sink drain used.
https://pantherrvproducts.com/37420/

[Bellinghamster]

Before seeing the last post, I would have bet money that it was some sort of checkvalve (likely a buoyant ball in the cylinder) to keep seawater from spitting up through the drain when crashing through waves or heeled to where the sink is under the waterline.

[GordMay]

I suspect it’s a P-Trap, c/w ADA Insulation.
Not normally used on boats.

[Tupaia]

what GordMay posted. A more compact version of the same thing is called a bottle trap.
https://www.cphart.co.uk/images/prod...APTRAPCP_4.jpg

[Calif.Ted]

Well no, it's not a P-trap or a J bend or anything more complicated than a way to connect a sink drain to a hose. Here's a link to the manufacturer's website, Camco who call it a rust proof drain system for campers and RV's.
https://www.camco.net/flexible-camper-drain-drain-37420

[Pete7]

Hmm, you will want marigolds on when you remove that.

Pete

[boatman61]

It's to drain any water before dismantling for cleaning the gunge out of the trap.

[NorthCoastJoe]

Has nobody looked under a sink and seen a trap before? It is to prevent sewage gases from coming up from the drain. This type is mostly used mostly in RV's. They do not meet the code rules for use in houses.

You don't need it if your drain is overboard, but if you had a greywater tank you would want it to keep the smells in the tank.

[Bowdrie]

From the pic it appears that it's not a P-trap and it doesn't work like one.
The water going into it will drain out once the water in the bowl reaches the bottom edge of the outlet hose.
The water in the bowl can never reach a level to close-off any "sewer gas" from going back up into the sink.
Go ahead, drop your ring in the drain, (would a Rolex go down the drain, ,) it should just fall to the bottom of the bowl.
Of course, maybe I'm wrong, (there might be an internal elbow or something of that nature).

[CaptTom]

Originally Posted by Bowdrie

...Of course, maybe I'm wrong, (there might be an internal elbow or something of that nature)...

I think you have a 50-50 chance of being right. Either it's (1) a "bottle trap" as @Tupaia described above, or it's just a "catch bowl" as in the RV version, per @Calif.Ted, also above.

[TrentePieds]

Shoreside hand basins are drained via a "tailpiece" leading to a "P"-trap. "P"-traps for handbasins are connected to the "stub out" from the "vent stack" in the building. The "stub-out" is 1¼" ABS pipe, formerly copper pipe.

As we don't have "stub-out"s in boats, and since we don't get "sewer gas" in boats and therefore don't require "P"-traps, this device is merely an adapter that permits connecting a shoreside basin installed in a boat to a seacock via hose.

TrentePieds