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Old 07-26-2020, 12:39 PM   #1
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Vac-u-flush.. Did I break it?

Heres the back story....

I have had the vac-u flush system on this and my last coach, and feel I am somewhat familiar with its operations, quirks and features.

So, my RV is parked at home, inside a garage that is not air-conditioned. I check on it regularly and we are not using it at all this summer with covid so it has been parked. So a few weeks ago, I flushed some water down both toilets and filled them back up just to use the system to keep up on things and the system and pump worked perfectly.

Heres where it goes down hill.

I left the switch on the last time and forgot to turn it off... AND it appears, that the water evaporated out of the bowls.

I was gone about 2 1/2 weeks and here in AZ its hot in July. The coach thermostat usually reads between 95 and 98 degrees ambient air temp. I do leave buckets and milk gallons filled with water around the coach to keep a bit of moisture in the air to not have everything completely dry out.

Anyways so I got back and went out to the garage for something else and I hear the pump start running.... I thought.... OH CRAP.... thats not good.

I run in and shut it off, like I said bowls are dry. So I turn on water pump and start filling both toilets back up. Both seem too be holding water but after experimenting with the vac-u-flush, it seems to be pumping fast and its not actually pumping. Maybe it's lost its prime or something? When the switch is flipped on, it immediately starts the pumping sound, faster than normal sound, and if I flush water doesn't go down fast and after multiple tries, Ive never got the sound or speed to change and I have always turned the switch back off manually as I am afraid to burn it up running it to long with no water.... but obviously the water Im flushing is eventually going somewhere, just slowly.

On a side note after about a week since this happened, both bowls are still holding water so the seals are still good. But air might have leaked into the system and lines when the bowls went dry. Also, I do have a BRAND NEW spare pump that I bought for about $800 and carry with me in incase of failure so I could call a mobile mechanic to switch it out our as both toilets run on the pump and if it fails I don't have a usable toilet.

Any ideas or suggestions are greatly appreciated.

Thanks in advance
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Old 07-26-2020, 01:58 PM   #2
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It's probably the duck bill valves in the pump...

Disclaimer... I've installed and maintained 3 Vacu-Flush toilet systems in boats, between 1995 through 2015... my knowledge and experience is on those systems. I assume they are very similar to the RV systems, but I've never seen, or worked on an RV system..

The sealand pumps are just a big diaphragm that goes up & down....

Their regular pumps (like an overboard discharge pump) have two duck bill valves, one on each side of the diaphragm chamber, that gives the "flow" directionality... without those valves the diaphragm will just go up & down without much resistance...

The vacuum pumps have 4 valves, two on each side of the diaphragm that give the pump both directionality, and allow for the vacuum to build...

It has been my experience that when the pump just runs, and doesn't sound like it's changing pitch (building any vacuum), either the duck bill valves have failed (dried out and/or warped so they can't seal) or something is blocking the valves on at least one side of the pump open...

Those pumps are pretty stout and hard to mess up... They can run for extended periods without damage... unlike the impeller pumps that can easily burn up if run dry for even short periods...

I had one pump that had crud build up in the pump chamber over the period of like 10 years.. One day, the crud was too thick for the diaphragm to go all the way down.. every time the pump tried to move, it would get jammed against the crud, and blow a fuse... I must have blown 4 or 5 fuses before I figured out what was happening... I took the pump apart, cleaned the diaphragm pump chamber, put in another fuse, and that pump worked for another 5 years... Those pumps are stout..

If the pump is cycling, but things aren't moving properly or the pump isn't building vacuum, always check the duck bill valves... They're cheap and easy to replace... Just remember to check their orientation... the valves are all the same, but the direction which they are placed in the pump, decide the direction of the flow... If they are put in wrong, they can work against each other and the pump won't work properly, or the pump will pump in the wrong direction... Once you see how they are installed, fit together, and their orientation.... it will make sense...

Good luck with the repair...
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Old 07-26-2020, 02:17 PM   #3
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Something to try before tearing into it..
A cup of calgon water softener and a good squirt of Dawn dish soap in the bowl, then fill bowl with water if it isn't already. do a manual flush and then refill bowl and repeat.. let sit overnight and see if the vac pump is working... It takes liquid in the pump plumbing to work properly..
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Old 07-26-2020, 03:17 PM   #4
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Thanks for the ideas.... as it is currently 110 I will wait till later tonight to try your ideas and see if anything improves.

I will update this thread tomorrow and let you know if I got anything to work or change.

Thanks!
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Old 07-26-2020, 03:40 PM   #5
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If it were me, I would swap in the backup pump and order a rebuild kit for the problem pump.
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Old 07-27-2020, 07:40 AM   #6
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Quote:
Originally Posted by Elwood58 View Post
If it were me, I would swap in the backup pump and order a rebuild kit for the problem pump.
Ditto. Sounds like pump rebuild time. We recently rebuilt ours (with a quiet pump); not a difficult job, just icky. Worked with this very helpful vendor: AquaStar.

Good luck!
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Old 07-27-2020, 07:45 AM   #7
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Duck bill valves. Obviously the pump is running. The diaphragm pumps virtually never fail.
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Old 07-27-2020, 08:10 AM   #8
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Duck bill valves. Obviously the pump is running. The diaphragm pumps virtually never fail.
That said, if you go to the trouble of duck bill valve replacement, might as well put bellows and o-rings in too. It will become your new spare.
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Old 07-27-2020, 09:50 AM   #9
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Duck bill valves. Obviously the pump is running. The diaphragm pumps virtually never fail.
Except when they do.
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Old 07-27-2020, 10:04 AM   #10
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Except when they do.
Agreed. It could be the duckbills or the diaphragm pump or both. If the pump fails, it is usually a separation of the diaphragm and the upper retainer ring halves. When this happens, the pump will eventually overflow if you continue to put water or effluent in it. It will be messy and disgusting.

I recommend changing it out with your spare (handy!) and rebuilding or having it rebuilt. Personally, at a cost of less than $100 for the pump, if it is more than a few years old, I would replace the pump, O-rings, and all four duckbills (assuming it is a vacuum style pump).

All of the rebuild parts should be less than $200. Ardemco is a great source for parts. Same price as everyone else, very knowledgeable and ready to help.

Easy (but disgusting) DIY project for someone reasonably mechanical with basic tools.
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Old 07-27-2020, 10:46 AM   #11
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Well I have spare duck bills that came with my new pump.... but.

Ive talked with a mobile rv mechanic that I know is good and I trust from multiple people I know that swear by him.

He told me that he doubts that its the duck bills and that he thinks after 40 years of experience that its actually the o-rings that have failed from running dry by what I am describing. He also said in over 100 of these pumps that he's worked on over the years, less than 10 have worked long term after a rebuild kit. He said that the labor time is the same to change the duck bills or just change the complete pump, so he's not in it for the money, but he's more than happy to get a guy on the phone that has had 4 separate leaks with rebuild kit, and would be ahead if he just replaced the pump day one.

If I pay him to come and just change the duck bills, and they fail or dont fix the problem, I still have the new pump on hand and loose maybe $150 in labor to change those parts.

I could attempt to do this myself but.... Ive never done this before and a few times I start something a little too technical and end up over my head, so I'm not sure that between my knowledge and the high temps if this is somthing not worth leaving to the professionals.

Thoughts?
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Old 07-27-2020, 04:49 PM   #12
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Well I have spare duck bills that came with my new pump.... but.

Ive talked with a mobile rv mechanic that I know is good and I trust from multiple people I know that swear by him.

He told me that he doubts that its the duck bills and that he thinks after 40 years of experience that its actually the o-rings that have failed from running dry by what I am describing. He also said in over 100 of these pumps that he's worked on over the years, less than 10 have worked long term after a rebuild kit. He said that the labor time is the same to change the duck bills or just change the complete pump, so he's not in it for the money, but he's more than happy to get a guy on the phone that has had 4 separate leaks with rebuild kit, and would be ahead if he just replaced the pump day one.

If I pay him to come and just change the duck bills, and they fail or dont fix the problem, I still have the new pump on hand and loose maybe $150 in labor to change those parts.

I could attempt to do this myself but.... Ive never done this before and a few times I start something a little too technical and end up over my head, so I'm not sure that between my knowledge and the high temps if this is somthing not worth leaving to the professionals.

Thoughts?
Well, given your reservations, it might be best to just have the repairman put in the new pump (make sure it has new duck bill valves)...

Then you can perform a real good flush/cleaning of the old pump, and take it apart at your leisure to learn/see how simple it really is...

When installing the system, there are general rules you need to follow... but if it's already, properly installed... just swapping out parts, depending on access, is pretty easy...

FWIW... in the many years I maintained my marine vacuflush systems, I lived aboard a 46C Hatteras for 15 years. I had two totally separate, redundant head systems on that boat to reduce the chances I'd be stuck offshore with no head... I maintained the two vacuflush head systems, and a third sealand pump for the overboard discharge..

The main head off the master stateroom was used daily, the guest head was used weekly... and the overboard discharge was used every two weeks at least, sometimes weekly....

In all that time, I replaced duck bill valves probably 6-7 times between all three pumps, and only replaced the bellows on a pump once....

Good luck with the repair...
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Old 07-27-2020, 05:34 PM   #13
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Just remember the plumbers motto. "Stuff" runs downhill and payday is Friday.

Yeah it a messy, unpleasant job but I look at it like this. It is either mine or I changed their diapers-except for the wife's-and I'll leave it at that.
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Old 08-05-2020, 12:22 PM   #14
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I know no one asked for an update..... but

Its been hot here and Ive not really been motivated, but I did go out and see if I could dig into it further and it only got worse...... And really I didn't do anything.

I decided to further investigate and here's what's now going on.

Pump still runs fast, and sounds like its running with no water.

When the pump is on and I flush a full bowl of clean water, not much happens..... meaning, if the water is going down, its really slowly with no pumping action like normal.

When running the pump I now see that I have water leaking from the area where the pump is mounted and the longer I run it the more water it leaks. I can not see exactly where it is leaking from and did not run it long enough to see that it was leaking previously.

Anyways I have resorted to calling the mobile RV repair mechanic, and scheduled him to repair it next Monday.
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