I plumbed the head directly into the holding tank. This frees up the 1.5" seacock and through-hull for discharging the tank and simplifies the plumbing and reduces the amount of hose involved. I then cut the hose that came from the tank pumpout fitting at the bottom of the tank about three inches above the top of the tank and put the diverter valve that was previously used for the head discharge line into the pumpout out line. One side of the pumpout line goes to the deck pumpout fitting. The other goes to a manual Whale-Henderson Mk. V diaphragm pump that is connected to the seacock and through-hull. This allows you to pump out the tank via either a pumpout facility or via the manual diaphragm pump when out past the THREE MILE LIMIT.
The Whale Mk V pump does fit in the head area, to the port side of the head itself. I cut a slot in the partial bulkhead that is just aft of the head, that crosses the head compartment, and the MK V's pump handle fits through the slot.
Some people have commented that you lose the ability to discharge the head directly overboard, but I don't see that as much of an issue, since anyplace you could have discharged the head directly overboard, you can DUMP THE TANK overboard instead. It requires an extra step, but there really isn't a functional loss of capability.
The simplified plumbing makes the boat more seaworthy and easier to troubleshoot. The 1.5" discharge line has a few things working as safety mechanisms now: First, you have the seacock, which should be closed unless actively dumping the tank. Since you don't dump the tank as often, you don't have to open this seacock as often. Second, the diaphragm pump acts as a check valve, since that is basically what a diaphragm pump is...two check valves in line around a bellows. Third, the diverter valve acts as a third closure for seawater intrusion. Also, since the diverter valve is mounted above the waterline, even if this were left open, it is unlikely that seawater would find its way into the holding tank.
You need to use a diverter valve, rather than just a 1.5" Y-splitter because the diverter valve itself acts to protect the manual discharge diaphragm pump from damage in the case you ever left the seacock open and tried pumping out the holding tank. Without the diverter valve, pressure from the pumpout system could force seawater back through the diaphragm pump, damaging it.
If you have any questions, please contact me via my blog.
tricruiser wrote:Hello Guys,
From what I have seen on my boat (new owner)and according the manual the only way to empty the holding tank is to pump it at a pumping station.
OK for lakes but when in open sea it is allowed to empty the tanks. looks like we cannot do it.
Does anyone done a modif to allow it?