Vacuflush woes

[Bob Bradley]

I’m struggling with a Vacuflush problem. Last season my vacuum generating pump was cycling on very regularly – at least once a minute. The bowl seal was leaking, so I presumed that was the cause of the problem. Over the winter I rebuilt the toilet’s flush seals, ball, etc. and reinstalled the head. I also rebuilt the vacuum generator pump – new bellows, duckbills, and O-rings. After installing the pump today, it ran for a few minutes before stopping. I flushed once or twice, and the new seal in the bowl held well. It regenerated vacuum after another minute or so, but 20 seconds later was running again. 2 minutes of running again before it had enough vacuum to stop. 20 seconds later it was running again, and then would not shut off a all. I finally gave up and turned it off after 5 full minutes.

Obviously, I have a vacuum leak somewhere in this convoluted system. I’m not sure where to start. There are 4 or 5 rubber plugs, most with wires for the tank level indicating system, pushed into the holding tank. I suppose any of them could be leaking – they are probably 20 years old. The vacuum pump is mounted on the holding tank with 4 ¼” machine screws. One of them is badly stripped. I’m not sure if that particular part of the system is supposed to hold a vacuum or not, or if one machine screw is enough to cause it to fail. I’m considering drilling and retapping it to 5/16”. The owners manual is not much help.

I know that the toilet is not leaking. I put a small amount of water in it and it did not draw down. With the pump running, it does seem to flush ok. I’ve only tested it with water so far. It’s a bit frustrating that after rebuilding the head and the pump, the problem has worsened.

Any experts here?

 

[madhatter1]

The vacuum shutoff switches can be temperamental from lack of use and also during colder temperatures. For example when we haven’t used the boat in a while neither head wants to stop pumping at first. Then when I flush it has a lot of power on suction. Then pump stops like normal. My guest head has a leak on the water lever shaft (air) so I leave that one off unless it’s getting used. The forward head works fine but every now and then either won’t stop pumping or will pump between flushes. So I turn that one off whenever I leave the boat.

Been that way since I bought the boat in 2018. One day I’m going to change out the shutoff switches.

 

[brettportzer]

We had a cracked plastic piece in the outfeed of the toilet between the bowl itself and the hose to the pump that gave us a similar result - it would flush ok but wouldn’t build a vacuum.

 

[Pascal]

Vacuum leak can only happen upstream of the vac pump. Anything downstream incl the holding is complete irrelevant. The only thing I m confused about in you description is the pump being mounted on top of the holding tank. Are you talking about the holding tank of the vacuum tank??

They are two types... a separate pump pump with a cylinder vac tank or what they call a vacuum generator with the pump mounted on top a small rectangular vacuum tank no more that a couple of gallons. That should not have any gauges or sender. The only thing on that tank should be the vacuum switch. If one of the holes into which the screws holding the pump is stripped, do not drill. I forgot how the pump is mounted by I m pretty sure the vac tank is a thicker there and the screw or bolt doesn’t penetrate they. Post a picture

There can be a leak somewhere in the base of the head some models have a soft seal at the base that can be crushed if over tightened.

Another possibility is that the duckbills got distorted when installing. I always used a little bit of liquid soap on the flange so they could rotate and avoided over tightening them.

Finally check the diohragm in the vac switch assembly. when the switches get old the rod that activate the actual electrical switch start dragging and sometimes don’t turn off the pump. Usually they won’t cause cycling though but you never know. I vaguely remember that the earlier styles had a plastic washer that would crack with age inside the diaphragm. I think the new ones had a metal washer

Otherwise turn off every source of noise including air con and try listening carefully. If the pump cycle every minute or two the leak should be audible.

 

[Eddieclemons]

I completely rebuilt my system last year. The system was unused in November and my started the same old problems. I ordered a new system from Scott and we are installing now. I wish I would have done it sooner. Good Luck, I hope yours is better than mine was.

 

[Bob Bradley]

I'll take some pics and post them later.

 

[Bob Bradley]

Here's a pic of the system.




I believe that the holding tank is the larger unit under the SM pump. The smaller one to its left is the vacuum tank.

 

[Pascal]

The small tank is definitely the vac tank, you can see the vac switch assembly. Waste comes in from the head at the elbow in the back then gets pulled by the vac pump

What is odd is that the outlet of the vac pump goes to another tank, not the one under the pump. Look at the outlet hose of the pump which disappears at the bottom right. And the macerator also pulls waste fro somewhere else also on the bottom right

It looks like that bottom tank is bypassed for some reason.

I would check the vac switch assembly. It s been a while since I ve use a VF but it seems like the switch base is not screwed on all the way. I would also check that white inlet elbow in the background. I recall on an issue with the seal one one of these. But that was years ago in a 70 footer I used to run.

Edit. The switch base itself, black part, is screwed in tight but that white flange isn’t.

 

[Bob Bradley]

Thanks, Pascal. That makes sense. The outlet from the pump goes to a Y valve, which gives me the option of flushing back into the tank or directly overboard when I'm offshore for 3 days with 6 guys. I'll check the flange. I also took someone's advice here to just throw parts and money at it til it works. I ordered a new switch last night.

Does anyone here know what model and make the tank is? The level indicators do not work and I'd like to repair them while I'm working on it. There are 3 or 4 white round fittings pressed into the top of the tank. They have light gauge wires coming from them. The connections seem ok, but the panel only shows the Empty and Full lights both on at all times. I haven't been able to gather any info about the tank so far.

 

[Pascal]

Can’t recall the name. Maybe it is a sealand product. You can take the big cap with the smaller caps off. Each small cap has a tube attached to it, various lengths, with a float. They trigger reed switches. Usually you just need to clean them up. Floats must be stuck