Black Water Problem

Hi,

Do you know if the tank level measuring you are using is accurate?

Adding bleach will kill any enzymes you want to add, enzymes generally take a few weeks to build up a reasonable base and to operate properly.

There is no magic bullet as such with this type of thing save yourself some grief and headaches get a tank cleaning company in to water blast and clean the tank and then you can use FW while you figure out the level measuring and OB Pumping arrgts.

How old is the boat? Older hatts used dip tanks that would corrode and eventually break off or develop holes preventing full pump out

I ve never seen sludge be a real issue

Firs make sure it s not a simple problem like weak vacuum from the pump out station (pretty common) or a clogged vent which causes a vacuum to build in the tank until the pump can't overcome it

"However, all of the old hoses have been disconnected and the old fittings have not been capped."

Obviously they need to be capped properly.

"Along with that, there is a large fitting in the center of the tank. It stands tall and looks similar to a seacock without a lever. On the side of it, a very long Headhunter line has been connected and it runs to the exterior starboard vent. (The line also has a coil that rests on the generator floor that is probably adds an extra 6 feet to the vent so I imagine it was temporary)"

I would shorten and make that hose run as straight as possible. If you can get good clean air flow into a holding tank you can promote the growth of aerobic bacteria and there by eliminate odors from the tank. In fact having 2 vent lines, one going to each side of the boat, is even better.
Otherwise you may need to install an inline vent filter which you can make yourself.

"At the very top of the fitting, it appears that the end cap is removable to serve as a very small sight gauge. I could not open it as the new PVC from the aft staterooms runs across it and I did not have enough time to take it apart yet."

I don't think I'd bother much with opening it. Make sure it's sealed well and get a good tank monitor and be done with it. Unless of course you can use it as the access port for the monitor.

"Coming out of the tank is another Headhunter hose that has a massive check valve on it."

Not sure what the point of the check valve is. You would be better served by having a ball valve there that you can lock off some how to show the USCG if you get stopped and inspected.

"There are three nearby seacocks that are all in use. I guess I could tap into one, splitting the line"

Bad idea. The black water over board should have it's own thru hull.

[[["Coming out of the tank is another Headhunter hose that has a massive check valve on it."

"Not sure what the point of the check valve is. You would be better served by having a ball valve there that you can lock off some how to show the USCG if you get stopped and inspected." ]]]

The purpose of the check valve is for the diaphragm pump. In case a solid keeps the check valve on the pump from closing there should be another check valve on the discharge and inlet side of the diaphragm pump about 3 feet in either direction.

We are also experiencing that we can't pump below 50% o/b. At the pump out on Sunday we got to 10% but jumped back up to 40% by the time we docked. How can you test if the air vent is free? How can you test if pick up is clogged?

surprising but a lot of boat owners have problems with plugged vents because they are too small this guy had his tank refilling with sea water after a pump out because of that
http://loopykiwi.blogspot.ca/search...:00-07:00&max-results=7&start=3&by-date=false

I have a similar problem, perhaps. I have Headhunter system with 200g black water tank that is treated with an ozone stream. After pumping out the black water (I do probably overdo the frequency, as I can't imagine having an overflow!) a constant stream of bubbles suggested the tank was drained. The gauge is not working - one says 0% all the time and the other stays on a reading of 2749g. Next thing, the heads start bubbling (non smell from bubbles), and the bidet let in a brown solution (treated, but definitely black water) via its plughole. Inspecting the overboard drain... I noticed that the "inverted U bend" of hose (the drain is below the waterline) didn't seem to have fluid inside, except near the bottom of the "up" side of the U. Could I have an air lock? What els eis stopping the pump pushing the black water overboard? The pump is Sealand ("TW?") pump is pumping away happily - but it does not drain the black water overboard.
(And btw the U bend seems to be attached via a new tube, to an empty, new PE tank (which Headhunter Inc site seems to show as a chlorine dispensing tank... but I use ozone....anyway... no idea what that's about!).
Thoughts anyone about a) how I should best clear the black water without incident and b) how I might avoid the air lock in future (if that is the only barrier to the drain working).

Many thanks in advance!

Check that your tank does not have blocked vents. Can you see anything being pumped out when you run the pump?

Thanks K1W1. Nothing comes out when pump is running. The vent is through the upper decks, exiting at roof. It was gurgling too... so, I'm guessing only, it's not a blocked vent.

Can you determine if there is actually anything in the tank?

Yes there is cos I've had 6 people aboard for a week!

Is there anyway you can use a water hose and try to push some fluid back down the line from the pump inlet to the tank? The suction might be blocked especially if some of those guests have been women who have dropped their sanitary surfboards etc down the toilet and flushed it

I can feed a hose into the OB drain hole and blast some water in there? I was worried about upsetting some delicate balance if I did that .....and btw the pump inlet comes from a pressurised header tank.

I am not familiar with your exact system but am familiar with a lot of pumps and tanks.

How does the header tank get pressurised?

How does the tank contents get from the tank to the header tank?

cdg: Apologies may have misled you! Here is the system described: The fresh water is pressurised in header tank... that feeds the heads...the heads flush with tough button activated Headhunter Royal flush system.... waste drops to MSD for ozone treatment... black water tank fills.. black water vents through roof of pilot house.... I manually discharge black water OB* as required (Sealand pump on top of black water pumps via that U bend tube over board.
*I could also mention the the PE box I mentioned above appears (um...haven't traced whole line yet as it requires many panels to come off) to have a tube that connects it to the top of that U bend just above the discharge outlet - but perhaps thats just from an old chlorine treatment system (which I read from previous skipper's notes was replaced by the current ozone treatment).