PART 2 - REPLACING THE RM69 AND RECONNECTING THE HOLDING TANK
I'm back! The story to-date: originally RM69 loo + holding tank in P275. RM69 old, service kit expensive. Replaced RM69 with Jabsco(illogical revenge) and blanked off holding tank.
What's new
Graham Ebb installed a holding tank on his new P285 and to empty the holding tank fitted a Whale Mk5 manual sanitation pump inside the hanging locker space in the loo. A nice flap covers where the pumpout handle is inserted and removed. My original question in this thread was "where can I fit a pump?". Before sharing my experience in copying Graham's wizardry I will mention that Sunflower has, I am told, a holding tank in the same wet locker space. When the out seacock is open, the waste goes from loo to tank and then straight out again into the sea. When the sea cock is closed, the waste stays in the tank. When the sea cock is next opened, the tank drains under gravity. Beautifully simple.
Learnings from fitting a pump to empty a holding tank
Shopping list. You will need:
- lots of money
- Whale Mk5 sanitation pump, under deck version BP0535
- plastic deck plate kit DP9906
- a three way valve
- 1.5 inch diameter sanitation pipe
- a heat gun
- maybe some right angle elbows and two jubilee clips per junction
Advice 1: the deck plate kit changed recently from a DP9905 to a 9906. When fitting the plate kit to the pump, notice that two of the four bolt attachment holes are obscured by the pump. Drill out the holes until the bolt can go in and out easily. If you don't, the bolt goes in fairly easily, cutting a thread as it goes, starts to bend and then refuses to come out. Sawing it in half and starting again is not fun.
Advice 2: even with a heat gun, classic white sanitation pipe is the devil's work and I will not use it again. Instead go to ASAP Supplies or Bainbridge and buy, at huge but worthwhile expense, flexible butyl rubber waste pipe
Advice 3: Eureka moment. With the original setup, one sanitation pipe went from anchor locker to holding tank, for pump out with a vacuum pump in certain ports. A second went from loo to holding tank. A third smaller pipe is the air vent pipe from tank to outside.
You cannot pump from loo through the Whale pump so we arranged the following:
- loo pumps directly into holding tank. No valves. Simple.
- cut the pipe from anchor locker to tank where it enters the tank
- fit a one piece three way valve there. Reconnect the anchor locker to tank. Connect the third exit to the Whale pump then up the anti syphon loop then to the out sea cock.
In other words, use the existing loo to tank pipe as a dedicated pipe to fill the tank. Split the line that goes from tank to anchor locker so it becomes a dedicated line to empty the tank.
The good news is that the three way valve really simplifies things. The bad news is that fitting the white sanitation pipe, which is inflexible to the extreme, is a nightmare. Finally, trying to mate the Whale to the bolts through the bulkhead wall when it is necessarily already attached to some sanitation pipe is very frustrating. After many tries, I used an extra long bolt through the bulkhead to line up one nut, then worked on the other three bolts, then returned and replaced the long bolt with a standard length bolt.
Advice 4: when we tried pumping out the tank, it started to collapse. The air vent skin fitting had blocked over the years. Getting it off was not easy. I could not hold the outside skin fitting while trying to undo the final turns of the backing nut. I first drilled a hole in the outside skin fitting so I could put a screw driver through it to act as a tommy bar. I still could not hold it so carefully cut it off outside with a saw. The new skin fitting (just an open hole, not a mesh like before) was too large to fit the fibrglass hull hole so you'll also need a file to enlarge the hole. Advice on boaty forums suggests that lack of ventilation means the tank gets extra stinky. Now the air is free to vent I am hoping for sweeter smells.
Advice 5: having fitted everything, including some right angle fittings, sadly, to get around some bends, we tried first the loo pump then the Whale pump. Alas many joints leaked, which was disappointing when using new pipe, and air gun and double jubilee clips throughout. A wipe of Fernox LS (leak stop) seemed to help. I'm not sure whether to do the rest with silicone sealant. I used Fernox because it's cheap and effective.
Will it all settle down and stop leaking? We'll see. If I started again, I would a) use butyl rubber sanitation pipe b) use sealant on all junctions. Once it is leak free, the advantage of this setup is that there are no valves to fiddle with except for a harbour-side pump out. Normally the loo always pumps to the tank and the Whale always pumps from tank to sea.
Ken