Jabsco and back pressure

[KayZee]

Hi!


The head is the standard issue production boat jabsco twist lock. When the boat was purschased used last July, the 1 1/4 waste lines were replaced both overboard and to the Holding tank. Everything was good until recetly when the emptying was less efficient requiring many more pumps to rid the bowl of it's contents. I also noticed that the T handle was pushing itself back up about half way but would within a few minutes would agree to stay down. HT was emptied via pump out and I did a little testing. The back pressure is only when going to the holding tank but whatever I send through the holding tank goes through and makes it to the OB discharge (tested with food dye). Pulled the bulkead to the tank. vent hose, clamshell vent and elbow to the HT are all clear. If it's only on the holding tank side it would have to be after the Y valve, wouldin't it? And what would hold air but not water? Could this be happening at the Head Valve and not after the Y? I have a full rebuild kit but you know, it's $60 or so bucks so I'd rather not just put it in blindly.



Appreciate any thoughts besides get a composter


Thanks,


Kurt

[Hartleyg]

Something (with a slow air leak) is blocking your tank line - pull the vent hose off the tank and try pumping into the HT - if that fixes it, look for blockage at the vent end (mud daubers LOVE tank vents!). If it doesn't, it's in the line to the tank, and the prime suspect is the Y-valve, though it could be anywhere.



Hartley
S/V Atsa

[chris mac]

Ours has done this, and it turned out to be a blockage in the hose (prior to the y valve in our case) a partial blockage allows seepage through so pressure will release over time.
We pulled the hose and were able to clear it into a bucket for removal. It's not a fun job.
If it's easily accessable, removal of both ends(tank emptied first) and capped off. Then remove the hose and replace or snake it in an area that can get dirty.
We do have a composting head as our second. Days like these tempt me to get a second

[peghall]

I suspect you have a blocked holding tank vent.


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.

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! 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

[KayZee]

Originally Posted by peghall

I suspect you have a blocked holding tank vent.

--Peggie

It really does sound like a clogged vent, doesn't it? Be that as it may, the vent both at the HT and the hull as well as the line between the two were checked before I posted.



thank you for your thoughts though.


Time to suffer the outrageous misfortune of hoses and valves.



Kurt

[KayZee]

Originally Posted by Hartleyg

Something (with a slow air leak) is blocking your tank line - pull the vent hose off the tank and try pumping into the HT - if that fixes it, look for blockage at the vent end (mud daubers LOVE tank vents!). If it doesn't, it's in the line to the tank, and the prime suspect is the Y-valve, though it could be anywhere.



Hartley
S/V Atsa

Not many Hartleys in the world. You're not the amp guy are you?


Tank vent was checked but I WILL do what you suggest in the name of research by leaving the vent outlet open and pumping the head.


thanks,


Kurt

[KayZee]

Update,


Checked all hoses to and from the holding tank and the waste dishcharge back to the head. All clear. Y diverter valve is clear. Problem is still the same. Today we work at the head end.


Kurt

[KayZee]

Fixed. The Joker was inside out. I didn't see which way it popped out of the elbow but it looked like an insdide out shirt sleeve. It looked in good shape; just one tiny line of daylite so I popped in the new spare I alread had in my hand and the head worked as it should and put this one back in spares. I don't think the pro yard guy that put the new waste hoses in put it in backwards. What I expect is that a pump out happend with the valves set in a way that the suction pushed or pulled the joker inside out.


I can't explain a mechanism for the back pressure now why it seemd like it was only on the HT side but there it is.



I appreciate the inputs,


Kurt

[Hartleyg]

Glad to hear you figured it out!



Hartley
S/V Atsa

[peghall]

Kurt, if a pumpout could pull hard enough to turn a joker valve inside out, that's a strong indication that you have a blocked tank vent...the pumpout was trying to pull in air anywhere it could find it.



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.

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! 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