My heads are backfilling with waste. There is back pressure when I try to empty the bowl. Also, it bubbles after I stop pumping. Seems like a vent problem, since it is happening in both heads. I have been tracing the lines but am not able to get to the vent. Also there is a waste pump connected to the lines that is not shown in the owners manual. I am going to replace the joker valves, but I don't think that is the issue. The line I presume is the vent line (white corrugated) disappears behind my closet. I also noted that the water inlet line to the toilet is somewhat collapsed (like it has negative pressure). Any help would be appreciated.
Hunter Legend 40.5 (1993) - Waste Backfill
- Thread starter Sdiring
- Start date
Not convenient but access is available behind the aft head cabinet or from the area behind the breaker panel. Sounds like a vent line issue but that doesnt always necessitate removal of the hose but rather making sure it is unrestricted (and the tank empty).
Welcome to the site.
As you become more and more desperate with this problem, one thing you shouldn't have a problem with is locating the fittings for the air vents on the exterior of the hull.
Work back from there and disconnect the hose from the hull fitting and push a pressurized hose against the vent hose. This may clear any blockage back into the tank. Also check the vent hose fitting on the hull. These can fill with who knows what.
As you become more and more desperate with this problem, one thing you shouldn't have a problem with is locating the fittings for the air vents on the exterior of the hull.
Work back from there and disconnect the hose from the hull fitting and push a pressurized hose against the vent hose. This may clear any blockage back into the tank. Also check the vent hose fitting on the hull. These can fill with who knows what.
I can't comment on the plumbing since what I see does not look stock. Mine also has an add-on overboard from a diverter valve. I second the notion that it is a blocked vent hose. I made up an exterior flush fitting for it from a small plunger head. Also, be sure the mesh screen is removed from the hull fitting. Just use a needle nose pliers if it is still in there. View attachment 206838
The classic indication that the tank vent is blocked.
All tank vents have two main functions: to provide an escape for air displaced by incoming contents and provide a source of air to replace contents as they're pulled out. When air displaced by incoming waste cannot escape out the vent the tank becomes pressurized, creating increasing back pressure that prevents the toilet from flushing.
Without a source of air to replace contents as they're being sucked out of the tank, the pump will pull a vacuum that'll prevent it from pulling out more than a gallon or two. A particularly strong pumpout can even implode a tank.
Do NOT use the toilet again or try to pump out or dump the tank until you've cleared the vent.
The two most common locations for a vent blockage are the vent thru-hull and the other end of the vent line--that end of the hose and the vent fitting on the tank. Start by cleaning out the thru-hull...use a screwdriver blade, ice pick--whatever works. If there' a screen in it, knock it out...screens create more problems than they prevent.If that doesn't result in a spew out the vent, you'll need to relieve the pressure before removing the vent line from the tank to clean them out...so open the deck pumpout fitting VERY CAREFULLY with a hose at the ready. Be sure you're UPwind of it! Scrape out that end of the vent line and the vent fitting on the tank...reconnect the vent line.
If there's a filter in the vent line, remove it...once a filter gets wet--which can happen when a tank is overfilled or even due to heeling--the charcoal swells and blocks the vent...one of the reasons why vent filters aren't recommended for use on most sailboats.
I also strongly recommend you replace the "vent" thru-hull (which are designed to keep sea water out of fuel and water tanks, not suitable for waste tanks, but boat builders use 'em anyway 'cuz it costs 'em less to use the same thru-hull everywhere) with an open bulkhead aka "mushroom" thru-hull. Not only will the allow more air exchange with the gasses in the tank, but it'll also prevent vent blockages by allowing you to put a hose nozzle against it to back flush the vent line every time you wash the boat and/or pump out. Anything that's tried to set up house keeping it will just get a water slide ride into the tank.
--Peggie
I can hear air flow through the vent and it pumps fine. I opened the pump out cover when I was having an issue and there didn’t seem to be any pressure. Just took out 20 gallons while I hard air flow through the vent. Replaced the joker valves today.
If the vent isn't blocked, the next most likely reason for back pressure is a serious buildup of sea water minerals or--in fresh water, urine crystals-in the toilet discharge hose... the result of using too little flush water and failure to rinse the line out before the boat will sit. That can reduce the diameter of a 1.5" hose to less than 1/2" which would definitely create back pressure. A 12-15% solution of muriatic acid--available from any hardware store--flushed all the way through the system (be sure to follow ALL safe handling instructions!), followed by a gallon of clean fresh water after 45-60 minutes is the cure. More than one application may be needed.
If none of the above, there's likely to be a partial blockage somewhere between the toilet and the tank...possibly in a y-valve. Could be as simple as, a guest flushed a wet wipe that's caught in it.
All that said...I just picked up on "it's happening in both toilets," which points to the tank vent. You may be hearing air going through the vent, but that only means it's not totally blocked but seriously reduced.
The two most common locations for a vent blockage are the vent thru-hull and the other end of the vent line--that end of the hose and the vent fitting on the tank. Start by cleaning out the thru-hull...use a screwdriver blade, ice pick--whatever works. If that doesn't result in a spew out the vent, you'll need to relieve the pressure before removing the vent line from the tank to clean them out...so open the deck pumpout fitting VERY CAREFULLY with a hose at the ready. Be sure you're UPwind of it! Scrape out that end of the vent line and the vent fitting on the tank...reconnect the vent line.
If there's a filter in the vent line, remove it...once a filter gets wet--which can happen when a tank is overfilled or even due to heeling--the charcoal swells and blocks the vent...one of the reasons why vent filters aren't recommended for use on most sailboats.
--Peggie
If none of the above, there's likely to be a partial blockage somewhere between the toilet and the tank...possibly in a y-valve. Could be as simple as, a guest flushed a wet wipe that's caught in it.
All that said...I just picked up on "it's happening in both toilets," which points to the tank vent. You may be hearing air going through the vent, but that only means it's not totally blocked but seriously reduced.
The two most common locations for a vent blockage are the vent thru-hull and the other end of the vent line--that end of the hose and the vent fitting on the tank. Start by cleaning out the thru-hull...use a screwdriver blade, ice pick--whatever works. If that doesn't result in a spew out the vent, you'll need to relieve the pressure before removing the vent line from the tank to clean them out...so open the deck pumpout fitting VERY CAREFULLY with a hose at the ready. Be sure you're UPwind of it! Scrape out that end of the vent line and the vent fitting on the tank...reconnect the vent line.
If there's a filter in the vent line, remove it...once a filter gets wet--which can happen when a tank is overfilled or even due to heeling--the charcoal swells and blocks the vent...one of the reasons why vent filters aren't recommended for use on most sailboats.
--Peggie