head vent

[workingonadream]

i have a 1979 46c hatteras. the holding tank is under the galley with no access.when i pump out there is still alot of vaccum in the tank when i release the pump hose. i think i have a venting problem but i do not know where the vent fitting is on the boat. i know it is not up high, so it must be down lower to the waterline. does anyone know where the vent fitting is on the outside of the boat. i have isolated all the water drains and shower sump, but still have a couple of fittings i cant account for. thanks.

 

[Andy B]

On my 43dc its at or below water line on stbd depending how full the water tank and holding tank are just last week I had to unclog mine and reroute the vent line cause it didn't pump out very well when it was underwater hope it helps.

 

[MikeP]

Got to wonder about a vent fitting being anywhere close to the waterline...sounds very un-Hatt like. It would seem to be one of the few times where something Hatt designed ought to be changed.

 

[Beckytek]

If the vent is under water, you will suck water into the tank as you pump out. It can't be underwater.

 

[Colwyn D]

Well it could be underwater. The water would not come in the vent as fast as the vacuum took the waste away and that would leave a vacuum in the tank. Won't be doing the tank much good either way.
On my 42c the vent fitting is on the port side about 2" above the waterline. With the original engines I would think it was barely out of the water.
If it was underwater and you flushed a head you should see bubbles coming from the vent?

 

[saltshaker]

i have a 1979 46c hatteras. the holding tank is under the galley with no access.when i pump out there is still alot of vaccum in the tank when i release the pump hose. i think i have a venting problem but i do not know where the vent fitting is on the boat. i know it is not up high, so it must be down lower to the waterline. does anyone know where the vent fitting is on the outside of the boat. i have isolated all the water drains and shower sump, but still have a couple of fittings i cant account for. thanks.

There should be a hatch in the companionway right in front of the door to the master stateroom. That will give you access to the top of the tank. That's were it was on my '74 46C and most other 46C and 45C series I that I've been on.