Vacuflush cycling question

marks737

marks737

Active Member
Sep 15, 2009
333
NJ
Boat Info
2005 390 Sundancer
Engines
Cummins QSB 5.9
My vacuflush system is cycling every couple of minutes. I've replaced the duckbills and toilet seals. I noticed that the o ring on the deck cap for pump out is worn and broken. So is it possible I'm getting a vacuum leak at the cap? Is there normally vacuum pressure at the cap?

My next plan would be to replace the bellows on the vacuum generator? Any other ideas or suggestions on how to trace this leak? Thanks.
 
No vacuum at the pump out cap.
 
is it building any vacuum and holding at all?

The white ball has to be cleaned too.. it gets defects on it and releases vacuum as well are you holding water?
 
I learned the hard way to check the system by taking off the hose coming from the head at the pump inlet, then blocking it off (holding a hand over it will work). Then run the pump and if it holds vacuum, the problem is upstream, otherwise attack the pump. The sanitation hoses on Sea Rays of our vintage had a rep for the hoses going bad so I wouldn't be surprised if that was a problem for you.
 
Also check the pressure switch on the vac tank for leaking, along with any of the "donut" seals there.

As mentioned above, the waste pump-out cap has nothing to do with this. The issue is from the vac tank (not the holding tank) to the toilet.

I didn't click that link above, but it appears to be for a Vac-Flush manual - that will have diagnostics in there.
 
I chased the master head cycling for several years and this stuff was worth it's weight in gold... It solved the cycling !
411SqXA75SL._AC_.jpg
 
nealtrombley said:
is it building any vacuum and holding at all?

The white ball has to be cleaned too.. it gets defects on it and releases vacuum as well are you holding water?
Click to expand...
Yes. It holds vacuum for about 2 min then cycles. No water leak in bowl.
 
I forgot to add, above, that if you let the vacuum build up... then turn it off and immediately get your ear around the vac tank, you might be able to locate the source by sound. If it's happening that fast, that helps.
 
For that fast of a leak down, and the bowl is holding water, I would suspect the vacuum generator.

As suggested, have someone flush while you place your ear near the vac generator. That big of a leak will make noise.
 
Does anyone have the diagram for which way the duckbills are supposed to go? I replaced them and the toilet bowl seal. That worked for a few days, then it started cycling again every 15-20 minutes. My next step was to replace the bellow, but I was so sidetracked that I forgot to pay attention to how the duckbills go back in. After putting back together, it now cycles every 8-10 minutes but for a much shorter time.. like maybe 5-7 pumps. I noticed that after taking the duckbills out and putting them back in, they seem to be like the old ones… a little bit open from use. Is this normal? I think I may have inadvertently installed one backwards the first time and maybe this damaged it a little bit affecting the seal? My next thought is to replace the pressure switch, but want to make sure I have the duckbills checked off my list. Thanks
 
The "mouth" of the duckbill faces the way the "stuff" would be flowing from. Just think it through... if they face backwards, how would the stuff get through? ;)
 
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