Black tank on ferretti

Perhaps your tank is back-filling with sea water? If the thru-hull valve is always open, try closing it to test.

-Chris

89 gallons should be adequate for 4 people. If it fills up that quickly you might have a sticking vacuum breaker in the vented loop in the discharge line which can cause sea water so siphon back into your tank. Cleaning the vent fixed it for me but drove home the fact that it is possible to sink your boat via the holding tank.

I am new to this site and do not know how to reply to two posts that people have made regarding the Black Water holding tank post that I made. Can someone guide me?

Please ignore previous post. I see the two posts by Ranger42C and Gsholz above. I will pass this info on to Ferretti. I am hoping that another Ferretti owner with the same tank capacity can chime in. To me it seems that the amount of fresh water being used on each flush is causing the issue. Ferretti says that 1 gal is used per flush. That seems very excessive to me. On my prior 60 Ft Sea Ray, I had a Sealand system and could control the amount of fresh water flushed by how long i held down the pedal. On this new Ferretti, i cannot control the water flow. It is pre set, and because the bowl is always vacumed to empty, one has to do a pre flush for a bowel movement, and then a flush, which uses twice as much water.

I had an issue where a head water valve was leaking just a bit. You could not see it without placing paper on the inner bowl.
It was the cleanest bowl on the ship, maybe that could be a hint.

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-Chris

Are your toilets a fresh water or seawater system. In my experience a seawater system is why they smell.