Vacu Flush shows "do not flush" light

SeaGreg

SeaGreg

New Member
Aug 2, 2015
79
Miami/Keys/Bahamas
Boat Info
2008 38 Sundancer
Engines
Mercruiser 8.1 DTS
I finally replaced my fresh water pump and SURPRISE my toilet doesn't flush! The bowl filled up with water yesterday and due to the pitch of the lift I found all the water had drained out and was sitting in the corner of the head's floor. I hear the pump pumping away when I turn on the breaker for the head but it won't flush, only fills up and the red light is illuminated indicating not to flush the toilet. Any suggestions?
 
Is the holding tank full?

Do not flush indicates a full tank OR insufficient vacuum to flush (newer systems only).
 
Empty tank. What causes insufficient vacuum and how can I mitigate this issue? Thanks in advance!
 
If the water is just accumulating in your bowl, you probably have a blockage in the line. Might also be time to replace the duckbill valves.
 
SeaGreg said:
Empty tank. What causes insufficient vacuum and how can I mitigate this issue? Thanks in advance!
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It's possible you have a bad sensor in the tank then. Do you normally see the Do Not Flush light come on after flushing? If you've never seen it before I'd have to guess its a bad tank sensor.
 
Jmwarren said:
It's possible you have a bad sensor in the tank then. Do you normally see the Do Not Flush light come on after flushing? If you've never seen it before I'd have to guess its a bad tank sensor.
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I just replaced the water pump yesterday and had never used the toilet since I had purchased the boat since there was no running water. The light seems to be red at all times, as soon as I flip the breaker.
 
If the vacuum pump is continuously running, it is probably not the sender in the tank. If the full sender connects, the relay kicks in which does two things - 1.gives you the red do not flush light, and 2. shuts down the vacuum pump. If the duckbill valves are original (2008), they are about at the point in their lives where they are going to be warped and no longer functional.
 
gerryb said:
If the vacuum pump is continuously running, it is probably not the sender in the tank. If the full sender connects, the relay kicks in which does two things - 1.gives you the red do not flush light, and 2. shuts down the vacuum pump.
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When I flip the breaker you can hear the pump making a rapid pulsating sound.
 
SeaGreg said:
When I flip the breaker you can hear the pump making a rapid pulsating sound.
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hold on.. which breaker? The fresh water pump... or the head? The vacuum pump "master head" doesn't really make a rapid pulsating sound... more like a kerplunk, kerplunk, kerplunk... as it tries to build up the necessary vacuum. The rapid pulsating sound is usually more like the sound of the fresh water pump trying to pull water from the tank and build up pressure.
 
"kerplunk" is the right sound! Yes, this occurs when hit the master head breaker. The fresh water pump only makes a sound if i turn on the water (which initially was all the time as I didn't realize the transom shower was slightly on... for about two hours)
 
Greg, that sounds like your vacuum pump trying to create vacuum. Once sufficient vacuum is created the light in the head turns green and the pulsating sound stops.

Normally there is a tell tail sign that your valves are going in that every so often the vacuum pump kicks in (I am here :smt001)......and over time kicks in more and more frequently until it never makes sufficient vacuum (you are here :grin:). There are seals (x2) in the toilet and also the duckbill valves that can need replacing. Might as well do both lots.
 
First step, take the toilet brush, some paper towels, clean the ball in the toilet. That can keep a vacumn from forming. Quick initial check if you have not tried it yet.

Mark
 
If the holding tank is empty _ you may have a stuck float on the sender. Toilet paper and other 'stuff' known to hangup there. Unscrew to sender and wash it down - quickly!:wow: Screw the sender back in.
 
Thanks to all of your help here I was able to fix the head... soemwhat, it still leaks but at least it produces a vacuum and also flushes. A small victory today within a series of battles in this project.
 
It amazes me what people ask and don't tell. What is somewhat fixed. what did you do? WTF is leaking? You only get help if you tell us the real story.
 
As mentioned previously Mike, the bowl filled up with water but didn't flush, the water would eventually leak out to the floor. Now the toilet flushes, and the water it refills with still leaks, slowly, out the side of the toilet where it is mounted to the fiberglass.
 
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Mike Blake said:
Post some pictures. That would help. Plus if the tank keeps filling it will take out your fart filter.
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I'll be back onboard tomorow and will take a photo. It seems that I will have to take the toilet apart and maybe replace gaskets. The boat was sitting on a lift and was unused for a year or so, there is a lot that needs to be done, nothing major as it surveyed really well (hull, running gear, compression tests, oil samples)
 
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