Toilet doesn't pump out when Y valve set to holding tank

[tomo123]

I have a Mirage 26 with a manual Jabsco pump and Jabsco Y valve to divert the waste to either the holding tank or to the ocean.

When the Y valve is set to pump out to the ocean the toilet pumps fine but when it's set to pump to the holding tank it requires a lot of pressure.

I can't pump until I move the valve to not be fully in line with the holding tank position and then there's a rush as if a vacuum was released. If I keep the valve not fully switched to the tank position I can pump it into the tank fine. The vent line on the holding tank is clear and I couldn't see anything blocking it but it's possible it's blocked right inside the tank.

Could this be an issue with the Y valve or a vent issue in the tank or something else?

I attached a picture of the valve and one of the tank.

[Mickeyrouse]

Sounds like a vent issue to me.

[AnsleyS]

I would suggest that you check the vent line from the tank overboard. The vent on the hull or the tubing itself may be blocked. Maybe put a water hose on the outside and try to push water back into the tank. if that does not clear it, you may have to remove and clean the vent and/or the tubing.

[pjShap]

It looks like you have an inspection port on the holding tank? If so, open the inspection port so it can function as a vent. If the pumping is then ok, you definitely have a clogged vent.

[hlev00]

I don't see how it is a vent issue if the only variable between working and not working is the position of the Y-valve. If it was a vent issue, you would have the same back pressure problem regardless of the position of the valve and it would never release.

However, what I don't have is a good idea of what the problem might be other than it is something in the y-valve. How long has this been going on? How old are the hoses and y-valve? Does water pump through as easily as air when it is in the magic position? All will tend to get a lot of build-up over time if flushing with salt water. If there is a lot of gunk built up around the outlet of the Y valve maybe the gate inside the valve has the one position where it lines up with a gap in the gunk.

Here is a video of the y-valve which might help understand what is going on. https://youtu.be/3JJJrYJHm8o

Harry

[pjShap]

Originally Posted by hlev00

I don't see how it is a vent issue if the only variable between working and not working is the position of the Y-valve. If it was a vent issue, you would have the same back pressure problem regardless of the position of the valve and it would never release.

When you pump overboard there isn't any venting required. The toilet bowl is the vent. When you pump into the holding tank, you have to displace air out of the holding tank to put liquid into the tank. If the air doesn't go out through the vent, the tank pressure increases, making it hard to pump.

[tkeithlu]

By the way, Tomo123, welcome to the forum.

[hlev00]

Originally Posted by pjShap

When you pump overboard there isn't any venting required. The toilet bowl is the vent. When you pump into the holding tank, you have to displace air out of the holding tank to put liquid into the tank. If the air doesn't go out through the vent, the tank pressure increases, making it hard to pump.

One of us is not understanding the OP's explanation."If I keep the valve not fully switched to the tank position I can pump it into the tank fine."

[Starbuck]

One of us is not understanding the OP's explanation."If I keep the valve not fully switched to the tank position I can pump it into the tank fine."

How does OP know that the toilet effluent is going into to tank when the Y valve is in mid-position? It's likely that changing the valve position opens up a pathway overboard. That would be consistent with all the given information.

[pjShap]

Originally Posted by hlev00

One of us is not understanding the OP's explanation."If I keep the valve not fully switched to the tank position I can pump it into the tank fine."

You're correct, I didn't notice that he said it worked fine with the valve partially switched. I don't see how that would give a vent path for the tank. If it's really pumping into the tank, and not mostly overboard, maybe a valve problem? It could also be going overboard, and still be a vent failure.

[gonesail]

holding tank is pressurized .. the vent is not clear.

[wyb2]

Originally Posted by tomo123

I have a Mirage 26 with a manual Jabsco pump and Jabsco Y valve to divert the waste to either the holding tank or to the ocean.

When the Y valve is set to pump out to the ocean the toilet pumps fine but when it's set to pump to the holding tank it requires a lot of pressure.

I can't pump until I move the valve to not be fully in line with the holding tank position and then there's a rush as if a vacuum was released. If I keep the valve not fully switched to the tank position I can pump it into the tank fine. The vent line on the holding tank is clear and I couldn't see anything blocking it but it's possible it's blocked right inside the tank.

Could this be an issue with the Y valve or a vent issue in the tank or something else?

I attached a picture of the valve and one of the tank.

Not a vacuum, pressure. It’s the pressure you’ve built up in the tank trying to pump into it, getting released overboard now that the you’ve moved the Y valve into a position where both ports are partially open. You can now pump the head fine because it’s simply discharging overboard through the partially open port.

It sure sounds like a plugged vent.

Looks like you have a tank-discharge macerator pump, does that work? The vacuum pulled by the macerator may pull the vent clog back down into the tank.

[peghall]

Blocked tank vent is right call.



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.

Do NOT use the toilet again or try to pump out or dump the tank until you've cleared the vent. 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.

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 'cuz if the tank is pressurized, there'll be a spew! 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.

After you've cleaned out the vent blockage, do one more thing: replace the "vent" thru-hull with an open bulkhead aka "mushroom" thru-hull (the kind your bilge pump uses). This will not only allow better exchange with the gasses in the tank, but will also let you put a hose nozzle against it every time you wash the boat or pump out to backflush the vent line. This will prevent future vent blockages.


--Peggie

[Scorpius]

Originally Posted by peghall

Blocked tank vent is right call.



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.

Do NOT use the toilet again or try to pump out or dump the tank until you've cleared the vent. 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.

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 'cuz if the tank is pressurized, there'll be a spew! 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.

After you've cleaned out the vent blockage, do one more thing: replace the "vent" thru-hull with an open bulkhead aka "mushroom" thru-hull (the kind your bilge pump uses). This will not only allow better exchange with the gasses in the tank, but will also let you put a hose nozzle against it every time you wash the boat or pump out to backflush the vent line. This will prevent future vent blockages.


--Peggie

Oh, I do so love my composting toilet!

[hlev00]

@tomo123 - In your original post you said "If I keep the valve not fully switched to the tank position I can pump it into the tank fine.". There is a lot of skepticism amongst others that you are actually pumping into the holding tank. It seems more likely that when you move the valve slightly that the pressure is being relieved via the pump-over thru-hull.

Have you tried pumping with your pump-over thru-hull closed and the y-valve in the partial position. If pressure builds in this test, then it means that you think you are pumping into the tank but in fact the vent is clogged and you are pumping overboard.