Holding Tank Vent 1” on port bow

[Packman]

I have attempted successfully to follow Peggy Hall’s advice on holding tanks with success except that I can’t find an appropriate 1” vent for the port bow which would adequately prevent water intrusion. I am thinking of having my 1” vent to end in a 1” tee and having the two tee branches lead into 2 1/2 inches of 1” hose to 5/8x1” reducing barbs that then vent into two conventional 5/8” vents at deck level, separated by 6” Does anyone have a better idea? A 1” mushroom vent won’t work on the port bow and would also look terrible. Peggy? Or anyone?

[peghall]

I have attempted successfully to follow Peggy Hall’s advice on holding tanks with success except that I can’t find an appropriate 1” vent for the port bow which would adequately prevent water intrusion.

A nice stainless or bronze thru-hull will look just fine...at least I've yet to run into anyone else who has a problem with it. It doesn't need to be right at the bow, just far enough forward to stay out of the water even in a knockdown. Water splashed against it won't put enough into the tank to notice (if you doubt that, try laying a 2 liter soda bottle on its side and aim a garden hose set on spray at it). If you expect to find yourself at sea in conditions that can keep your decks awash for awhile, put a shutoff valve on the vent line or a seacock on the vent thru-hull that you can close till it's over.



-Peggie

[Packman]

Thank you Peggy, I am appreciating all of your advice but I just can’t agree that I can place a fully open vent here. Here is a pic where I currently have the 5/8 inch vent. To replace this like you describe, the larger open vent would need to be a few inches lower than this one. The vent will often be under water and facing forward given the curve of the bow. I think it would need a clamshell cover which would be unsightly compared to two 5/8” inch vents. The open area of the two 5/8” vents will be approximately equal to a 1” vent and they will enter unreduced into 1” tubing since the tee will be a 1” tee. I am not an engineer but it seems like it would work configured in the way I have described. Would you think that is the case and do you have any further comments?

[tmarks11]

Are you sure that you can't just expand that hole downward, so that the top of the existing hole stays in the same place? That worked for me, and I replaced the 5/8" hooded vent with a stainless flanged fitting. It looks pretty good.

In my case, I replaced 5/8" with 3/4".... not as much of a size increase but that was all that would fit where the current fitting was located because of what was on the inside of the hull.

https://www.groco.net/products/fitti...ies/hthc-750-s

[peghall]

If you're not comfortable doing that, then don't. But don't run a single vent line off the tank to a tee going to two thru-hulls either...'cuz air will only travel across the top of the tee from thru-hull to thru-hull without going through the tank. If you want two vent lines, run two off the tank. If that requires adding another vent fitting on the tank, that's actually pretty easy to do, thanks to a li'l gizmo called the Uniseal UNISEAL



--Peggie