Vacuflush losing vacuum after duckbill/bellows replacement

Team PCBeach

Team PCBeach

Active Member
Oct 12, 2010
183
Boat Info
360 Sundancer 2003, SIMRAD 3G Radar, Raymarine Autopilot
Engines
Twin 8.1L Horizon
Vacuflush system on 2003 360 Sundancer. Systems started cycling the pump every couple of minutes. I took too long to address it and actually burned out the plump.Tank was holding water so my research said it was the duckbills. Replaced all duckbills and the pump bellows while had it off the boat. Stole the pump from the discharge line since we never use that. Reinstalled and pump is still cycling. Couldn't get right back on it due to surgery so have just been turning the pump on/off as we needed to use the head. Ready to get back on it now and just wondering if there is anything else that could be causing the leak other than maybe I just didn't get something seated correctly the first time.

Also thought it might just be easier to buy a complete pump housing with pump and replace everything since I need to replace the discharge pump anyway.

This is the first time I have ever worked on the vacuflush so just looking for guidance from those who have spent more time on it than me.
 
If you're not using the discharge pump, there's really no reason that you have to replace it.

Yes, it's possible you didn't get something seated properly. But the leak could be a number of other places... the inlet or outlet at the vac tank, the pressure switch... and of course somewhere along the line to the head (not nearly as common, though).

I'd start by letting it run a bit and then shut it off and have someone with good ears move around and listen to these spots. Sometimes you get lucky and can hear it.
 
Discharge pumps are not the same as a vacuum pump. They only have one set of duckbills vs two so that could be your issue.

upload_2022-4-20_14-10-50.png
 
If you tightened the piping too tight when you replace the duckbills, they will not hold their shape. Looking at the drawing above, it appears you could use the discharge pump by utilizing the two black ABS pipe nipples with the 2 other duck bill valves. However, may not be the same.

Does the bowl hold water when the pump is pumping and the ball is closed? If the bowl is not holding water, then the bowl seal is bad. There is also a brass shaft between the ball in the bottom and the pedal. It links the foot pedal with the ball. There is an o-ring on this shaft that will wear out over time and will cause a leak.

Bennett
 
quality time said:
Discharge pumps are not the same as a vacuum pump. They only have one set of duckbills vs two so that could be your issue.
Click to expand...
If I understood his first post correctly, he simply swapped "motors", even though he used the word "pump" (and apparently I did, as well). But, yes, if the entire setup was swapped, that could be the issue.
 
bahamabreisus said:
I always wondered if there was more difference than that. Discharge is way less than Vac Pump
Click to expand...



When I re-hosed the sanitation system on our boat, I replaced all the duck bills even though they were fine, I just figured I might as well, and IIRC, the T pump body and fittings that house the duck bills are left hand thread. S-pump =RH
 
Yes for clarification I just took the motor from the discharge and used it on the Vac pump. I have done a little more research and believe changing out the entire pump is way more expensive than I thought because I had been looking at discharge pumps and now realize the discharge and vacuum pumps are not the same. I will follow @Lazy Daze tip of seeing if I can hear a leak. If not I will just pull the vacuum pump and clean/reseat everything.

I still want to get a motor for the discharge. Even though I have not used it doesn't mean I never will, and I don't like to leave things "broken".
 
I don't know but I've read here that the Oring installation on the pump cover when changing the bellows can cause leaks if not seated right.
 
I had a similar problem. After replacing duck bills, bellows, pressure switch. I then replaced ball, seals, and brass shaft in the toilet and that solved the problem.
 
Had similar problem last year. Toilet bowl holding water and vacuum pump cycling every few minutes or so. Removed intake hose off tank and plugged with a large rubber cork. Turned on system, pump pulled up suction and held it for hours. Ruled out tank, pump, etc. Reconnected hose to tank, problem returned. Had to between toilet and tank. Decided to replace toilet seals etc as I hadn't done it since getting boat. In disassembling the toilet base found a rusted mounting bolt from toilet base. Removed and replaced base, problem solved. Certainly didn't expect to find a rusted through bolt, but it appeared it wasn't properly protected by the gasket like the others were when installed.
 
I had an issue similar on my guest system. I changed everything from duck bills, to new pressure switch and it stilled cycled every 10 minutes. I finally just replaced the pump and vacuum tank with a new one.....problem fixed! Expensive yes, but the bowl was holding water and I did not have any cracks in the line. Sometimes, it's just time for new.
 
I went through this too. Mine turned out to be the pressure switch itself being worn out. Having said this, each of the recommendations above are valid and should be ruled in or out as you trouble shoot. Lessons I learned when I replaced my duckbill valves:
1. Make sure that all 4 are pointed in the right direction
2. Each should be well silicone greased
3. Do NOT over tighten the spin on collars or you'll crush the DVB rims.
4. Bellows O ring must be greased and seated properly when reassembling the pump.
 
The bellows seal O-Ring number 7 (upper one) is a tricky little devil to get installed correctly. If you replaced the bellows then check to make sure you got the O-ring seated. My lesson learned. Also if the duckbill housings are over-tightened they will definitely crack the pump body - you will have vacuum leaks in the tiniest of cracks.
vacuum-pump-spec-diagram.jpg
 
ttmott said:
The bellows seal O-Ring number 7 (upper one) is a tricky little devil to get installed correctly. If you replaced the bellows then check to make sure you got the O-ring seated. My lesson learned. Also if the duckbill housings are over-tightened they will definitely crack - you will have vacuum leaks in the tiniest of cracks.
vacuum-pump-spec-diagram.jpg
Click to expand...

Been there...done that myself. It is tricky!

Bennett
 
ttmott said:
The bellows seal O-Ring number 7 (upper one) is a tricky little devil to get installed correctly. If you replaced the bellows then check to make sure you got the O-ring seated. My lesson learned. Also if the duckbill housings are over-tightened they will definitely crack the pump body - you will have vacuum leaks in the tiniest of cracks.
vacuum-pump-spec-diagram.jpg
Click to expand...
bbwhitejr said:
Been there...done that myself. It is tricky!

Bennett
Click to expand...

What's the trick to doing it correctly?
About to go down this road... unfortunately
 
It seems like every time I change duckbills it takes a few days to stop cycling. I think the hose to the pump just doesn't properly seal right away, I might crank on the hose clamp again. After it stops, no problem.
 
Shaps said:
What's the trick to doing it correctly?
About to go down this road... unfortunately
Click to expand...

The biggest trick I found was to use plenty of silicone grease. When you dismantle it, you will see. I have rebuilt both of mine. The first one almost drove me crazy. The 2nd one was easy. Using the grease to hold it in place really helps.

Also on the first one, lining the bellows up to get the bolt to attach to the motor was very easy. The 2nd one was a pain in the butt. What was easy on one, was difficult on the 2nd one. Murphy's law I guess....

Bennett
 
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