I know this topic has been covered a bazillion times in this Forum. My factory installed Jabsco manual toilet on a 2007 H-31 back fills about 1/2 bowl no matter how many times I pump in the dry mode. Toilet is plumbed to a holding tank and the tank connects to thru hull to the outside world. The discharge thru hull is wired closed and the pump out line is used to empty the tank as per regs. I have replace the joker valve twice in one year. I replace the top valve gasket this spring to successfully fix a no water into the bowl problem and got a good look at the the pump assembly and rubber parts. All looked good so I put a dab of petroleum jelly on the O ring and re installed. My question is - with the thru hull for the inlet water from the lake to the pump closed and the pump handle all the way down shutting off the bottom of the bowl to/from the discharge line going up to the holding tank - where is the water coming from to get back into the bowl?
Jabsco backfilling
- Thread starter Jerry21707
- Start date
It is coming from the holding tank. Black water is not all that black.
check the tank vent If you are pumping into a badly vented tank then the pressure will force water back back into the head. Also consider the water levels in both the tank (full and empty) and the head. A full head (50% due to pumping and 50% due to stuff that never gets pumped out) can also "seek its own level" in the head. I received a 50% tank from the PO and was scratching my head because "it fills up really fast and I cant seem to get 40 gal (my tank capacity) out of it during pumpout". The problems was the tank was 50% full of solids that did not get sucked out during pumpout. Tested ti by pouring a measured amount of water into the tank via the pumpout port. 20 gal from empty to full in a 40 gal tank told the tell.
A great way to check the vent is to take off the pumpout cap. note if there is positive or negative pressure as you open the cap.. Should be none at all if the vent is working correctly.
check the tank vent If you are pumping into a badly vented tank then the pressure will force water back back into the head. Also consider the water levels in both the tank (full and empty) and the head. A full head (50% due to pumping and 50% due to stuff that never gets pumped out) can also "seek its own level" in the head. I received a 50% tank from the PO and was scratching my head because "it fills up really fast and I cant seem to get 40 gal (my tank capacity) out of it during pumpout". The problems was the tank was 50% full of solids that did not get sucked out during pumpout. Tested ti by pouring a measured amount of water into the tank via the pumpout port. 20 gal from empty to full in a 40 gal tank told the tell.
A great way to check the vent is to take off the pumpout cap. note if there is positive or negative pressure as you open the cap.. Should be none at all if the vent is working correctly.
Agreed that the water is from the holding tank cause the intake thru hull is positively shut to lake flushing water. More for my benefit of how the system works - I wonder how the black water can make its way back down into the bowl when the pump handle in all the way down and the plunger is seated in the bottom of the cylinder blocking access back into the bowl. I can see how the cylinder could fill up and many even leak water out of the air hole if the lever were in the "wet bowl" position (which it is not).
It sounds like you have a seriously pressurized system, most likely due to a blocked tank vent. When air displaced by incoming material can't get out the vent, it pushes back against anything it can...in this case, back down the hose to the toilet. Be grateful that it's able to relieve the pressure by sending bowl contents back where they came from. Usually it's an eruption in the toilet or a guyser when the deck pumpout cap is opened, or a burst tank.
If it is a blocked tank vent, you won't be able to pump out or dump the tank. If no air to replace tank contents can be pulled into the tank through the vent, the pump will pull a vacuum that'll prevent anything from being pulled out of the tank. If the pumpout is a particularly strong one, or your tank has thin walls, that can result in a cracked tank.
It's also just possible that there's a blockage in the head discharge plumbing...a clog--somebody flushed a wet wipe or something else they shouldn't have, or a huge wad of the wrong kind of TP for use in a marine toilet, or sea water mineral buildup that's seriously reduced the diameter of the hose......that can push back pretty hard too.
You need to stop using the toilet until you've found and solved the problem. Start with the tank vent...the most common place for a blockage is the vent thru-hull...scrape it out with a screwdriver blade, ice pick or whatever works...if there's a screen in it, knock it out...screens cause more problems than they solve or prevent. If you don't find anything, check the vent line connection to the tank--both that end of the vent line and the fitting on the tank (I'd open the deck pumpout cap before removing any hoses if I were you).
If it's not the vent, start interogating those who were aboard immediately before this started...find out what might have been flushed. (And let this be a lesson to you as to WHY it's VERY important to explain to guests what can and cannot go into a marine toilet). Then we can help you figure out how to dissolve whatever it is without having to take anything apart.
It just occurred to me that what you're seeing may NOT be back flow, but flush water. You've said the inlet seacock is closed, but are you 100 certain that it really is? That the handle may be in the closed position, but the valve is still open? Seacocks do fail.....worth checking.
How dirty is the water that's coming back into the bowl? How high is it rising relative to the waterline?
If it is a blocked tank vent, you won't be able to pump out or dump the tank. If no air to replace tank contents can be pulled into the tank through the vent, the pump will pull a vacuum that'll prevent anything from being pulled out of the tank. If the pumpout is a particularly strong one, or your tank has thin walls, that can result in a cracked tank.
It's also just possible that there's a blockage in the head discharge plumbing...a clog--somebody flushed a wet wipe or something else they shouldn't have, or a huge wad of the wrong kind of TP for use in a marine toilet, or sea water mineral buildup that's seriously reduced the diameter of the hose......that can push back pretty hard too.
You need to stop using the toilet until you've found and solved the problem. Start with the tank vent...the most common place for a blockage is the vent thru-hull...scrape it out with a screwdriver blade, ice pick or whatever works...if there's a screen in it, knock it out...screens cause more problems than they solve or prevent. If you don't find anything, check the vent line connection to the tank--both that end of the vent line and the fitting on the tank (I'd open the deck pumpout cap before removing any hoses if I were you).
If it's not the vent, start interogating those who were aboard immediately before this started...find out what might have been flushed. (And let this be a lesson to you as to WHY it's VERY important to explain to guests what can and cannot go into a marine toilet). Then we can help you figure out how to dissolve whatever it is without having to take anything apart.
It just occurred to me that what you're seeing may NOT be back flow, but flush water. You've said the inlet seacock is closed, but are you 100 certain that it really is? That the handle may be in the closed position, but the valve is still open? Seacocks do fail.....worth checking.
How dirty is the water that's coming back into the bowl? How high is it rising relative to the waterline?
The water refilling the tank is clear. The sea cock for the flush water is confirmed closed. The water back flowing into the bowl stops at about 1/2. It could be the level of the water outside the boat. I have not measured that. As far as a blocked tank vent if I removed the pump out cap therefore creating a working vent and the bowl does not refill after dry pumping would that confirm a blocked wast tank vent. I still do not understand how the water from any source can get back into the toilet bowl if the pump handle plunger is seated in the bottom of the cylinder.
The water refilling the tank is clear.
I'm pretty sure you mean the toilet... It's NOT coming from the tank. a) that's impossible unless the tank is full to overflowing because the inlet on the tank is at the top...and while waste is full of lively li'l bugs, it can't jump up into a hose connection.
Clear water can only be flush water running into the bowl. It could just be "rinse" water left in the head discharge line, but half a bowl is an awful lot to be that. That it is clear and rises to the boat's waterline is a bit scary. Yes, the intake seacock is closed, but the water has to be coming from somewhere.
As far as a blocked tank vent if I removed the pump out cap therefore creating a working vent and the bowl does not refill after dry pumping would that confirm a blocked wast tank vent.
In theory, but it's not foolproof.
I still do not understand how the water from any source can get back into the toilet bowl if the pump handle plunger is seated in the bottom of the cylinder.
I'm not sure it is. We need to spend some time on the phone 'cuz I have a bunch more questions that need answers for me to get to the bottom of this...stand by for incoming email.
I'm pretty sure you mean the toilet... It's NOT coming from the tank. a) that's impossible unless the tank is full to overflowing because the inlet on the tank is at the top...and while waste is full of lively li'l bugs, it can't jump up into a hose connection.
Clear water can only be flush water running into the bowl. It could just be "rinse" water left in the head discharge line, but half a bowl is an awful lot to be that. That it is clear and rises to the boat's waterline is a bit scary. Yes, the intake seacock is closed, but the water has to be coming from somewhere.
As far as a blocked tank vent if I removed the pump out cap therefore creating a working vent and the bowl does not refill after dry pumping would that confirm a blocked wast tank vent.
In theory, but it's not foolproof.
I still do not understand how the water from any source can get back into the toilet bowl if the pump handle plunger is seated in the bottom of the cylinder.
I'm not sure it is. We need to spend some time on the phone 'cuz I have a bunch more questions that need answers for me to get to the bottom of this...stand by for incoming email.
Don't put petroleum jelly on rubber parts use Teflon LUB the petroleum jelly will cause premature failure