Vacu flush heads not holding vacuum

[discovery]

Hi Peggy,

I have a 2002 Hunter passage 456 with two original vacu flush heads, on our trip to the Caribbean this past season one of the heads would not retain vacuum so we used it then turned it off, this past month when we commissioned the boat here in Grenada I decided to resolve the issue, I had suspected the duck valves which I have changed before but it had been 3 years, so I changed all 4 of the duck valves on both heads and changed the bowl seals also, the heads are holding water but after a flush the pump,comes on and runs for 18 seconds or so then shuts off and 2 minutes later it runs again and keeps this pattern until it's turned off. So clearly a issue but where, I have checked all the fitting with shaving cream as you suggested and have found no culprit, I assume it's the bellows? Both heads will not hold the vacuum but do hold water, could the bellows be bad on both units? How do I check they it appears they are sealed in the Marlon casing? Is there a way to visually check also a way to repair, I'm in Grenada and parts will be very hard to find I assume. Are there any parts on the bowel that could be the issue? I have tried tightening and loosening the big hose clamp, that doesn't seem to make any difference?

 

[sailor420]

There is also an o-ring in the peddle that could lead to loss of vacuum. Also the vacuum gauge could of gone bad.

 

[discovery]

It does pull a vacuum afte 30 seconds of pumping ant it flushes fine, but that vacuum is gone soon after, its not holding it, so I think its escaping from somewhere so in don't think it's the switch unless it's a place that can allow the vacuum out. The pedal sounds like a possibility I just didn't know if it was a possible culprit here.

 

[Peggie Hall HeadMistress]

, the heads are holding water but after a flush the pump,comes on and runs for 18 seconds or so then shuts off and 2 minutes later it runs again and keeps this pattern until it's turned off.

In an 11 year old system that's still original except for replacing some duckbill valves, it's entirely possible that you have more than one problem...starting with a failed vacuum tank switch (those have an average lifespan of about 5 years) that's cutting the pump off way too soon, 'cuz 18 seconds isn't long enough for the pump to establish anywhere near the amount vacuum (9-11 psi) needed...so the pump keeps cutting on again trying to get there.

It's not out of the question that the bellows in both 11 year old pumps could be worn out and leaking air. The vacuum pump housing is two pieces--a top and a bottom, held together with 6-8 screws...sealed with a rubber gasket. Open it up to see and/or replace the bellows. Or if you're lucky, the pumps are just packed with a buildup of waste and TP that are never rinsed out as a result of believing SeaLand's claim that the VacuFlush only needs a pint of water/flush.

And then there's that pesky o-ring in the pedal assembly.

Could be any or all of the above or something else. You might want to give SeaLand (who now answers the phone "Dometic") a call...330-439-5550 or 800-321-9886

 

[Mikem]

I had that issue with my aft head. Rebuilt head, replaced duckbills, tightened all fittings and still would not hold vacuum...would cycle intermittently. Turns out it was the 90 degree fitting that emptied into the holding tank. The fitting had a hairline crack all the way around the fitting and when bumped it broke clean off. Replaced the fitting and voila all is well.

 

[discovery]

Thanks all, I will continue working on it, anyone got ides on how to get to this pesky o ring on the pedal assembly?

 

[discovery]

The initial pump to creat the vacuum is about 30 seconds, the 18-20 seconds is the pumping after it finally switches off and sits for 2 or three minutes. So I guess it's got a head start on the vacuum and just needs to add to it. I will check out the bellows and try and figure out how to see the o ring. Hope it's a size I can get at a hardware store down here in Grenada.