holding tank valve and thru hull questions

[Shayne]

went to a dock side pump out to drain the black water tank and basically was just pulling sea water, no black water. I shut a thru hull in the forward crew and two in the gene room. i found one blue one and one yellow in the gene room. holding tank valve.jpg

I tried the three way valve attached to the holding tank in every position and still did not pull black water, only sea water in all three positions. any tips? I'm lost.

[SEVEN]

Are you sure you have not been pumping overboard all the time?

[Shayne]

I have not seen any black water coming out when we flush the heads and we are on a floating dock so i think I'd notice. I was thinking to flush some milk to assure it does not go overboard.

What's the procedure to empty the holding tank? do i have to close the sea strainer to all heads on board before pump out?

[SEVEN]

Turn off the valve that leads overboard and open the one that leads to the top of the holding tank. Each boat has something different so I’m not sure 100% until I see photos. Can you add them? Do you have two holding tanks? If so is anything pumping out of the other. Try pouring food die and flushing to see if it appears underneath.

[SEVEN]

Dye, sorry

[MadHatter53]

There’s only one way I can think of for you to be pulling seawater from the pump out is thru the macerater and If that’s it someone switched the hoses.

[Captain Ralph]

I remember duck bill valves sucked backwards on a strange install allowing green water to get pumped up dockside.

Has your system ever worked?

Time to close all thru hulls and tag them. Then follow each hose till this gets figured out.

[Shayne]

Thanks everyone. Left her in key largo but when I return I’ll continue to investigate.

[SKYCHENEY]

I've seen this happen on many Hatts. It's usually one head that causes it. From the fwd head, there is a line that goes to a thru hull. There are two valves there. One to open it up to dump that head directly overboard and one to open/close from a tee to take direct it to the holding tank. If you leave both valves open, it will fill the holding tank with sea water. Look at all of the lines near the heads. Follow them to the thru hulls and check all of those valves.

[rwaldrop13]

Well this is startlingly similar to what I just ran into removing the toilet from the fwd head because we decided to eliminate it. PO told us that head was not connected to holding tank (correct), so when I remmoved the original Galleymaid toilet I saw water in the 3-inch discharge line. I started following it thru the pump in the lazarette underneath, and the discharge line from the pump disappeared thru the bulkhead into the generator room. I got down there and discovered the hose had literally disappeared - hidden under the shelf the starboard battery bank is on, apparently run thru a void space into forward bilge of starboard engine room. That valve was still open. Closed the valve, disconnected the pump end and mounted it over forward shower sump with plug in line. I figured having it over shower sump means anything leaking past valve will go right back overboard, and exercise shower sump pump at same time.