Tip for Vacu-Flush Air Leaks

[EngNate]

A tip for locating vacuum leaks in Vacu-Flush head installations:

Check the obvious, of course - hose clamps, bottom bowl seal, duckbill valves. If it loses water from the bowl, the bowl seal needs cleaning or a service kit.

Turn the vacuum pump off; Hold the pedal down until the water fills into the bowl and release it. Turn the pump on for 30 seconds, then switch it off; Go all along the plumbing and listen - air leakage will make a bubbling noise inside the hose. A mechanic's stethescope can be very useful for this.

At this point, if you haven't found the leak(s), it's either the o-ring on the pedal shaft, or the one on the vacuum tank switch ass'y, or the vacuum switch diaphragm.

[Dreaming Yachtsman]

Originally Posted by EngNate

At this point, if you haven't found the leak(s), it's either the o-ring on the pedal shaft, or the one on the vacuum tank switch ass'y, or the vacuum switch diaphragm.

By "o-ring on the pedal shaft", do you mean the "SPRING CARTRIDGE", item12 in the parts list on p. 15 of the manual? Is there an O-ring in that cartridge that can be replaced?

Redid all the hose connections between the pump and vacuum tank then used a stethoscope as suggested but could hear no bubbling. Toilet still loses enough vacuum to cycle the pump every few hours. This symptom started about 1 month ago. Previously the system had been tight (no pump cycling between flushes) for 9 years.

[wingless]

How do the duckbill valves look?

When they are installed are the fittings snug or tight?


Does the bowl lose water over time?


On mine, the waste line has a PVC pipe that is a slip fit into a grommet on the vacuum generator. If that leaks, then the pump will cycle.

[jgbrown]

Originally Posted by Dreaming Yachtsman

By "o-ring on the pedal shaft", do you mean the "SPRING CARTRIDGE", item12 in the parts list on p. 15 of the manual? Is there an O-ring in that cartridge that can be replaced?

Redid all the hose connections between the pump and vacuum tank then used a stethoscope as suggested but could hear no bubbling. Toilet still loses enough vacuum to cycle the pump every few hours. This symptom started about 1 month ago. Previously the system had been tight (no pump cycling between flushes) for 9 years.

The cartridge connects to a shaft that connects to the ball under the toilet bowl brass or plastic. Did you replace the ball, spring cartridge etc? They usually come together as a kit. Lubricate o-ring on shaft before assembly. I use a thick silicone grease, just a smear.
Is the vacuum tank an all in one with the pump and rectangular, or the style with a separate cylindrical tank? We see more failures and leaks around the vacuum switch on those.
One easy way to isolate, pull hose off toilet, use a sea land fitting glued in a pvc ball valve.
Let the system build vacuum. No cycling? It's the toilet. Still cycling? It's the pump/tank/hoses.
Easier and faster to hire someone with the correct vacuum gauge for testing, but it's kinda expensive if you're only repairing a single toilet system where many of the parts you might throw at the problem should likely be replaced anyways. E.x the shaft which can corrode badly and fill the system with corroded brass

[jgbrown]

Originally Posted by Dreaming Yachtsman

By "o-ring on the pedal shaft", do you mean the "SPRING CARTRIDGE", item12 in the parts list on p. 15 of the manual? Is there an O-ring in that cartridge that can be replaced?

Redid all the hose connections between the pump and vacuum tank then used a stethoscope as suggested but could hear no bubbling. Toilet still loses enough vacuum to cycle the pump every few hours. This symptom started about 1 month ago. Previously the system had been tight (no pump cycling between flushes) for 9 years.

The cartridge connects to a shaft that connects to the ball under the toilet bowl brass or plastic. Did you replace the ball, spring cartridge etc? They usually come together as a kit. Lubricate o-ring on shaft before assembly. I use a thick silicone grease, just a smear.
Is the vacuum tank an all in one with the pump and rectangular, or the style with a separate cylindrical tank? We see more failures and leaks around the vacuum switch on those.
One easy way to isolate, pull hose off toilet, use a sea land fitting glued in a pvc ball valve.
Let the system build vacuum. No cycling? It's the toilet. Still cycling? It's the pump/tank/hoses. Move to the tank, repeat. Don't try this past the tank, as the switch is then disabled.

Easier and faster to hire someone with the correct vacuum gauge for testing, but it's kinda expensive if you're only repairing a single toilet system where many of the parts you might throw at the problem should likely be replaced anyways. E.x the shaft which can corrode badly and fill the system with corroded brass chunks and grit.

[Dreaming Yachtsman]

Originally Posted by wingless

How do the duckbill valves look?

When they are installed are the fittings snug or tight?


Does the bowl lose water over time?


On mine, the waste line has a PVC pipe that is a slip fit into a grommet on the vacuum generator. If that leaks, then the pump will cycle.

Replaced all 4 duckbill valves.

All fittings are tight.

Bowl does not lose water.

All fittings here are hose clamp or threaded.

[wingless]

Originally Posted by Dreaming Yachtsman

Replaced all 4 duckbill valves.

All fittings are tight.

The duckbill fittings should be snug-only. If they are tight, then they could deform.

Originally Posted by Dreaming Yachtsman

All fittings here are hose clamp or threaded.

Do you have an image of the fitting from the head to the vacuum generator?

All the ones I've seen look like below, w/ a slip fit on a 1¼" PVC pipe.

[Dreaming Yachtsman]

Wingless,
Your image shows exactly how our starboard Vacu-Flush is plumbed. The port one, however, is a bit different in that the pump sits beside the tank in a "low-profile" configuration. The input and output fittings are the same, though, hose over the PVC pipe. I cannot get to the fitting on the bottom of the toilet without destroying the base the toilet is mounted on.

This picture shows the mess of hoses and pipes:

The question still remains, is there an O-ring in the shaft cartridge that can be replaced? We are 400 miles from a Vacu-Flush dealer.

[jgbrown]

Originally Posted by Dreaming Yachtsman

Wingless,
Your image shows exactly how our starboard Vacu-Flush is plumbed. The port one, however, is a bit different in that the pump sits beside the tank in a "low-profile" configuration. The input and output fittings are the same, though, hose over the PVC pipe. I cannot get to the fitting on the bottom of the toilet without destroying the base the toilet is mounted on.

This picture shows the mess of hoses and pipes:

The question still remains, is there an O-ring in the shaft cartridge that can be replaced? We are 400 miles from a Vacu-Flush dealer.

Yes there is. Remove toilet bowl, remove spring cartridge, rotate ball open, plug output hole inside toilet with paper towel. Rotate ball totally upside down(I use an adjustable wrench on the square part of the shaft). Remove Philips screw, push shaft into upside down ball valve(may shed lots of corroded metal, the reason for paper towel in hole below).

Edit: look for 'rotor shaft' included in sealand kit 385318162

Just rolled out an o ring on a spare shaft, diameter of shaft in groove under o ring is 0.375"
Outside diameter of o ring off the shaft is about 0.513"
Thickness 0.067". Measurements are as close as I can get with a squishy o ring. Should get you close enough to buy some to try.
Shaft uses 2. Silicone grease on both.

[Dreaming Yachtsman]

Because both Vacu-Flush units on board are leaking, I decided to spring for a vacuum test guage which comes with a detailed flow chart for isolating a leak. Inserting the plug into various openings determines whether the leak is upstream or downstream of the plug. Start by placing the plug in the 1" orifice in the bottom of the toilet bowl to rule out the flush ball. Then work your way towards the vacuum tank.

Of course I neglected to read the instructions before pulling the hose off the inlet to the vacuum tank, thereby "splitting the system" as recommended by jgbrown a couple of posts ago. At this point, my new vacuum guage has not dropped a needle width in 1.5 hours so the leak is obviously on the toilet side, probably an O-ring on the ball shaft. I'll check that location tomorrow.

[Dreaming Yachtsman]

The leak was through the flush shaft O-rings. Installed a new flush ball and shaft kit (Dometic P/N 385318162) and the pump hasn't cycled for over 8 hours.

Also replaced all four duckbill valves in the other unit and its pump has stopped cycling as well.