Head vented loop question

[Jhubs81]

Originally Posted by mitiempo

I don't think there is a need for a vented loop between the holding tank and the through hull. Open the valve when pumping and close it when not. Worst case some salt water gets in the holding tank.

If I could at least remember what I had for lunch today, I might be trusted to remember to open and close that valve! Murphy has been a steady shipmate for years. My main concern is that the vented loop has worked fine for several years with just normal periodic cleaning and now it doesn't. I know something's wrong but I just can't figure out what?!? The novelty of it venting into my wife's hanging locker is rapidly wearing off so I may be forced to seal off the vent out of self preservation...

Thanks,
Hubs

[kmacdonald]

Originally Posted by Jhubs81

If I could at least remember what I had for lunch today, I might be trusted to remember to open and close that valve! Murphy has been a steady shipmate for years. My main concern is that the vented loop has worked fine for several years with just normal periodic cleaning and now it doesn't. I know something's wrong but I just can't figure out what?!? The novelty of it venting into my wife's hanging locker is rapidly wearing off so I may be forced to seal off the vent out of self preservation...

Thanks,
Hubs

Just be thankful it's not YOUR hanging locker.

[AndyEss]

Originally Posted by kmacdonald

Just be thankful it's not YOUR hanging locker.

You apparently don't know sheeit from shinola - or have never been married

If momma ain't happy, everyone knows. If daddy ain't happy - who cares?

[Dmeistar]

Thanks for all the great input everyone! I ended up routing the hoses to the existing vent. I should have waited for responses but the situation was, how shall we say....urgent.

I realize a vent that is too low is probably worse than no vent at all, so we're going to have to work on this thing. I have found a place I can take the loop higher above the waterline and have something to mount it on. BUT--do I need to move the siphon loop itself? What if I just clamped a hose over it and ran the hose up to the high point?

[kmacdonald]

The siphon loop needs to be 6 to 8" above the heeled waterline. Running the vent hose higher is not the same. The best place for the vented loop is somewhere near the center line of the boat. If it's next to the hull you won't be able to get it above the 6 to 8" above heeled waterline in most cases. I chose not to have a vented loop because my toilet bowl top is above resting waterline. A lot of boats have the toilet on a platform to raise it high enough. It could still siphon in water when heeled but that hasn't ever happened and I would be on the boat to catch it anyway. I close the seacock when away from the boat.

[kmacdonald]

I don't know if anyone has mentioned it but if you can't get the vented loop 6 to 8" above the heeled waterline it is best to vent the vented loop overboard instead of using a valve on top of the vented loop. The valves require a certain small vacuum to open and that requires the 6 to 8" water column.

[peghall]

I've never heard that before...I think you need to recheck the source of that information. The valves aren't supposed to open to let air into a line through which water is being pushed, only to break a siphon in a line through which water is being pulled...which is why intake vented loops must be installed between the pump and the bowl. The air valve in a vented loop in the line between the thru-hull and pump open to prevent the toilet pump from priming.


Vent lines on vented loops are a bad idea because they're so small--only 1/4"--that they quickly become clogged with salt and sea water minerals, turning the loop into an UNvented loop that no longer has any ability to break a siphon.



--Peggie