Y-valve or T connector below the waterline

[mario101]

Hi,
I am working to modify my holding tank (installed above waterline) to allow pump out (actual connection) and discharge (natural flow no macerator if possible) in the water. Somewhere in the path I need to install a Y valve and a T connector.
I read somewhere that Y valve is not recommended to be installed below waterline (kind of understand lower reliability as compared to a hose). It is a "hard" requirement or only a recommandation? What about a T connector - can be under waterline ? (double clamped of course).
thank you for any suggestions , comments.
Mario

 

[Joe]

Never heard that Mario. I'm not sure relying on gravity to empty your holding tank is wise, it'll be interesting to hear Peggy's comments. You don't need a macerator, but I'd think a good, hand operated waste pump would help things move a lot better. Otherwise you'll have a messy hull. If the thru hull is under water, then the waste won't clear farther than the waterline without some help......yecchhh!

 

[mario101]

Never heard of it (Y-valve below waterline) but I saw this comment on a vendor page (looking for a Forespar Y valve).
http://www.defender.com/product.jsp?path=-1|51|106370|813148|316446&id=101893
Also I realized that the original Y valve installed by manufacturer (Beneteau) is above water line (is a strange position and always wondered why they didn't installed lower in a more convenient position ).
Thank you for the comment regarding thru-hull below water line(it is) never tought about it..

 

[Peggie Hall HeadMistress]

You can't do it. However, there's another way that will work

Instead of a y-valve in the existing tank discharge line, install another discharge fitting in the tank. It's actually pretty easy to do, thanks to a gadget called the Uniseal UNISEAL If you have at least 5" clearance above the tank you can put the new fitting in the top of the tank, with a piickup tube inside the tank.

 

[Joe]

Yes, I saw that disclaimer in the forespar ad.... but couldn't find anything else to support it.... here's an old Don Casey article, kind of like the West Marine Advisor piece.... and there is no mention the issue. http://www.boatus.com/boattech/casey/13.htm

Mario, after a little more looking I found this article describing a K.I.S.S. system that sounds very similar to what you proposed.... http://www.charlesekanter.com/editorial MSD.htm .... Note that his solution to keeping the below waterline portion of gravity powered discharge line is to flush it with water through the tank... with the bowl pump. So my negative comment might have been hasty. Also, his system doesn't employ a Y-valve on the discharge side..... instead simple Tee or Y fitting just be fore the thru hull is sufficient... close the seacock, the pumpout line becomes functional. Open the seacock and the gravity discharges the tank, you pump water through the system witht the toilet's pump. Pretty simple.

 

[mario101]

Thank you Joe.
Really helpfull!

 

[Waybad]

Groco and others make a three way bronze ball valve and I have been using it on my thru hull for 20 years. just replaced it and it still looked good. turn one way drains sink turn other way drain tank or head. They make them in 1 1/2 inch, 1 inch and 3/4. Also if worried or ever needs replacing shut off thru hull and replace. Waybad

 

[mario101]

Groco and others make a three way bronze ball valve and I have been using it on my thru hull for 20 years. just replaced it and it still looked good. turn one way drains sink turn other way drain tank or head. They make them in 1 1/2 inch, 1 inch and 3/4. Also if worried or ever needs replacing shut off thru hull and replace. Waybad

Thank you Waybad
Mario101