NC11 discharge holding tank

[bobmotor]

Hi there,

I recently bought a second hand NC11 and it’s my first boat and struggling with the badly translated users manual!

Waste water from the heads goes into the holding tank, which is getting pretty full up. I am trying to figure out how to empty the tank whilst out in the open water.

I turn on the valve under the sink that says “Flushing Outlet” and then press the macerator pump button. The pump makes a lot of noise and the gauge moves back slightly but it never actually discharges the waste water to the sea.

Can someone please tell me where I’m going wrong?

Much appreciated

[rene460]

Hi Bob, welcome to the forum and congratulations on your purchase.  You will find many friendly, like minded people here, and a wealth of information in the archives, well worth browsing through.

But first, a near full holding tank is approaching being an emergency.  I don’t know the specific system on the NC 11, but all the systems are minor layout variations of the same basic components.  

There are basically two methods used to empty the holding tank, and generally both are installed.

For emptying at sea, the basic system is a gravity drain from the bottom of the tank to a through hull valve and out.  The valve is low down against the inside of the hull.  On our SO30i it was under the berth in the aft cabin.  Lifting the mattress and the base board gave access.

For emptying to shore based facilities, there is a deck level outlet.  Looks rather like the fuel or water fill points, but different label.  This deck fitting has a tube inside the tank which reaches down to near the bottom of the tank.  The a Camlock fitting screws into the deck outlet and the shore facility has a hose and a vacuum pump to empty the tank.  A little exploration behind all the panels near the holding tank should quickly reveal what you have.

You mentioned a mascerator.  In some installations, this has a manifold that allows pumping out, but I am not familiar with all the variations on that theme.

Generally the outlet from the toilet is pumped by hand pump or electric pump to the top of the tank.  Some installations have a three way valve which allows the toilet to be pumped either to the tank or overboard.  Once the effluent is in the tank, it is either drained by the gravity drain I mentioned earlier or sucked out via the deck fitting to the shore facility.  I know that sometimes the gravity drain is omitted, possibly due to local regulations, then once the effluent is in the tank, you need the shore based facility.

You mentioned a “flushing outlet” valve.  It is possible that is used to flush the toilet directly overboard, but I don’t know for sure. Put some water in the bowl, and see if it is emptied by that route.   If it is intended for emptying the tank, the mascerator inlet would need to come from the bottom of the holding tank.

The main thing is to examine around the tank, and around the toilet and follow each pipe until you know where it goes.  Then it will be obvious what to do.  

I hope this little description helps you to know what you are looking for.  Nothing beats the joy of having the right tanks empty and the right ones full!

rene460

[Hanzel]

Hi Bob,

Recognize your problem, we have had exactly same.
First of all, discharge is only allowed at open sea xx km out of the shore.

When you look into the cabinet under the sink in the headroom, you seen just above the ‘flushing outlet valve’ a black in-line valve.
Inside this valve (to be opened with 4 small bolts) you find a rubber diaphragm avoiding water coming in, however when the outside valve is closed, no possibility for water coming in so: we removed the rubber diaphragm to have lower anti-pressure pumping out.
During pumping out you must hear the macerator is under load and the gauge indicates lower volumes.
When this is not the case, fill the black watertank completely, remove the floor under the stairs so you can see the topside of the black water tank and be sure the tank is really full (and even a bit pressurised).
Than, during macerator action, put your weight on the topside of the tank and you see the macerator starts pumping like hell.
We think that at some moment the macerator is getting to dry and doing afore the macerator is filled with sh#t and starts pumping.

Succes and enjoy your NC11
Hans

[bobmotor]

May 27, 2023 20:21:25 GMT Hanzel said:

Hi Bob,

Recognize your problem, we have had exactly same.
First of all, discharge is only allowed at open sea xx km out of the shore.

When you look into the cabinet under the sink in the headroom, you seen just above the ‘flushing outlet valve’ a black in-line valve.
Inside this valve (to be opened with 4 small bolts) you find a rubber diaphragm avoiding water coming in, however when the outside valve is closed, no possibility for water coming in so: we removed the rubber diaphragm to have lower anti-pressure pumping out.
During pumping out you must hear the macerator is under load and the gauge indicates lower volumes.
When this is not the case, fill the black watertank completely, remove the floor under the stairs so you can see the topside of the black water tank and be sure the tank is really full (and even a bit pressurised).
Than, during macerator action, put your weight on the topside of the tank and you see the macerator starts pumping like hell.
We think that at some moment the macerator is getting to dry and doing afore the macerator is filled with sh#t and starts pumping.

Succes and enjoy your NC11
Hans

Hi Hans,

Thank you very much. I will give that a go next time the tank is full. I managed to go into a marina over the weekend and used their pump-out facility to empty the tank for now.

[bobmotor]

May 27, 2023 11:25:07 GMT rene460 said:

Hi Bob, welcome to the forum and congratulations on your purchase.  You will find many friendly, like minded people here, and a wealth of information in the archives, well worth browsing through.

But first, a near full holding tank is approaching being an emergency.  I don’t know the specific system on the NC 11, but all the systems are minor layout variations of the same basic components.  

There are basically two methods used to empty the holding tank, and generally both are installed.

For emptying at sea, the basic system is a gravity drain from the bottom of the tank to a through hull valve and out.  The valve is low down against the inside of the hull.  On our SO30i it was under the berth in the aft cabin.  Lifting the mattress and the base board gave access.

For emptying to shore based facilities, there is a deck level outlet.  Looks rather like the fuel or water fill points, but different label.  This deck fitting has a tube inside the tank which reaches down to near the bottom of the tank.  The a Camlock fitting screws into the deck outlet and the shore facility has a hose and a vacuum pump to empty the tank.  A little exploration behind all the panels near the holding tank should quickly reveal what you have.

You mentioned a mascerator.  In some installations, this has a manifold that allows pumping out, but I am not familiar with all the variations on that theme.

Generally the outlet from the toilet is pumped by hand pump or electric pump to the top of the tank.  Some installations have a three way valve which allows the toilet to be pumped either to the tank or overboard.  Once the effluent is in the tank, it is either drained by the gravity drain I mentioned earlier or sucked out via the deck fitting to the shore facility.  I know that sometimes the gravity drain is omitted, possibly due to local regulations, then once the effluent is in the tank, you need the shore based facility.

You mentioned a “flushing outlet” valve.  It is possible that is used to flush the toilet directly overboard, but I don’t know for sure. Put some water in the bowl, and see if it is emptied by that route.   If it is intended for emptying the tank, the mascerator inlet would need to come from the bottom of the holding tank.

The main thing is to examine around the tank, and around the toilet and follow each pipe until you know where it goes.  Then it will be obvious what to do.  

I hope this little description helps you to know what you are looking for.  Nothing beats the joy of having the right tanks empty and the right ones full!

rene460

Thank you for the welcome and the thoughful reply. I saw your message yesterday morning before I went to the boat and indeed took your advice and followed all the pipes that made sense and everything was as I was expecting. I'm 99% sure I'm doing everything right but just not getting the pump working. I'll do what Rene suggested and put pressure on the tank next time I'm trying to pump and see if that works.

[bobmotor]

I just thought I'd update this thread just in case any one else has the same problem.

I had the lovely people at Hamble Yacht Care install a diverter valve which would allow brown water to be discharged straight into the sea or to the holding tank. Whilst doing that, they realised the secondary macerator pump which was meant to discharge the brown water was fouled. They took it out and serviced it which fixed the issue.

[Hanzel]

Thanks for the update Bob.
Just curious to know, how difficult was it to take the macerator pump out as the available space is sooooooooo tight….
Did they use the square opening above the bowl or ?……