Head holding tank not completely pumping out

[kristinamarieat45]

Do any of the Beneteau owners have a issue with a head holding tank not completely pumping out??
We bought a 2014 Beneteau Oceanis 45, and the front head holding tank will not pump out the last 6 or more inches on the bottom.
Our dealer inspected it and said that there is approx 5 inches of space from the end of the tube to the bottom of the holding tank.
see attached diagram.
Beneteau claims there is nothing they can do.
Does anyone else have this problem???
Attached is a drawing I got from Beneteau on the forward holding tank.

 

[Jackdaw]

Most if not all modern Benis use dip-tubes to empty the holding tank. The advantage is that all of the fittings are on the top of the tank, which reduces the chance of catastrophic failure.

The downside is that the tank will not fully empty. Normal procedure is to suck the tank, fill with water, suck and repeat. What ever is left will be 99 percent water.

 

[kristinamarieat45]

Most if not all modern Benis use dip-tubes to empty the holding tank. The advantage is that all of the fittings are on the top of the tank, which reduces the chance of catastrophic failure.

The downside is that the tank will not fully empty. Normal procedure is to suck the tank, fill with water, suck and repeat. What ever is left will be 99 percent water.

Thanks for reply Jackdaw.
We spent all of last season, being extremely thorough with extra rinsing and suck/repeat.After first pump, we would fill the tank over half full with fresh water 2X. Even after this we noticed that this head definitely had a slight odor (remember it was a brand new head unit) - unlike our aft head with same treatment. That's why at end of season we told the dealer about the trouble.
Interestingly enough, the dealer told us that after we pump out, to add some fresh water and then open the over board through hull that will drain the tank completely.
I am alittle uncomfortable doing this because of the location of where we pump out.
And I know you said that it should be 99 percent water left, but is hard to believe that when watching the tank with a flashlight and it not looking that way.
Not sure why they just could not replace the too short dip tube.

 

[JRacer]

Did B offer any logic for why the pipe does not go closer to the bottom of the tank? Or was it just trying to save the cost of 5 inches of pipe on a 45 foot boat?

 

[kristinamarieat45]

Did B offer any logic for why the pipe does not go closer to the bottom of the tank? Or was it just trying to save the cost of 5 inches of pipe on a 45 foot boat?

Our Dealer said that Beneteau could not do anything about it.
It seems to me, that someone really screwed up.
Either the install of the tank, or the manufacturer of the tank.
I was just inquiring if any other owners have experienced this.

I realize that most owners do not use a flashlight on side of tank to check if tank has emptied (its a dark area where the tank is installed in the foreward head).
But we had issues on our other boat, and got in the habit of while pumping out, one of us is below watching how much pumps out and how full to fill the tank with water when rinsing the tank.
Thus we noticed immediately after commissioning that the tank would not fully empty. Our hope was they would fix this!

 

[Jackdaw]

The bottom of our dip tube is cut on and angle and the tip almost touches the bottom. It gets almost everything out. I would not be happy if the tube was 5 inches from the bottom. But my tank is also wide and flat, not tall. 5 inches is 1/3 of my tank's height!

The tank is a 3rd party product... I assume it was delivered to beni that way.

 

[Gunni]

Interestingly enough, the dealer told us that after we pump out, to add some fresh water and then open the over board through hull that will drain the tank completely.

Doing so is a violation of the law anywhere in the Chesapeake Bay. Looking at your tank diagram, I do not believe that you are losing a significant volume of tank capacity with that dip tube configuration. Tight tanks with good vents do not smell. You could take the tank out, remove the dip tube, clamp a section of flexible waste hose on and cut the end at an angle so that it could reach the bottom...but I wouldn't until I had exhausted other remedies.

If you have odors take a look at your tank vent system, perhaps increasing the hose diameter. Evaluate your waste hose run lengths, long runs full of waste can generate odors. Use more effective flush regimes. Know your head pump volumes, and hose volumes and determine how many cycles are needed to push clean water through your waste hoses.

I would also evaluate your tank management process; You are operating a bio-system, you want a healthy colony of aerobic bacteria in there. That means no chlorine / antibacterials and using one of the nitrate type additives. (Odorlos is one).