Holding Tank Filling Up

[edbulmer]

Whenever we do a pump out my holding tank fill up with water. I have found one through hull valve for each head and they are closed. The were left closed last winter during dry storage, could they have frozen and cracked. These are major fittings and look quite solid. Viking 44 aft cabin. (macerator has been isolated and disabled.)

[transmitterdan]

At the top of the holding tank there should be a small fitting connected to a hose that usually runs somewhere to the hull skin and a fitting. This fitting allows air to enter the hose and flow into the holding tank when pumping out. As the tank fills again in normal use the air in the tank is expelled through this fitting. It sounds to me like this hose is plugged up and not allowing air to flow back and forth. If this vent hose is clear then when pumping out there will be no tendency to suck water into the tank.

The thru hulls on the heads are probably not the problem. My guess is that the water is coming in via another thru hull valve that is connected to a manual pump that is designed to empty the tank when out at sea.

[edbulmer]

Thant manual pump has been disabled.

[skipmac]

Originally Posted by edbulmer

Thant manual pump has been disabled.

How is it disabled? Is it completely disconnected and removed from the hose or just turned off or is the seacock connecting it to the water closed?

Depending on the kind of pump if it is still connected depending on what you did to disable it, it can still allow water in by the suction of the pump out pulling water through the valves in the pump.

[skipmac]

Bottom line, I agree that Dan's suggestion is the first place to start. Check the vent hose to the holding tank to see if it's clogged up. Don't know if they have them in Canada but in the SE USA there is a kind of wasp called a dirt dauber that makes a nest of mud likes to use little holes like that for the nest.

[transmitterdan]

Originally Posted by edbulmer

Thant manual pump has been disabled.

From where do you believe the water is coming? (had to avoid ending sentence in preposition due to recent grammar police action)

[skipmac]

Originally Posted by transmitterdan

From where do you believe the water is coming? (had to avoid ending sentence in preposition due to recent grammar police action)

While I do appreciate proper grammar I do try to avoid police action but occasionally cannot resist when I see "your" confused with "you're"

Regarding final prepositions, I submit the following quote, supposedly from Winston Churchill about an editor that "corrected" one of his manuscripts to eliminate a sentence ending in a preposition.

“This is the sort of bloody nonsense up with which I will not put.”

So preposition away and be in good company.

[peghall]

If the tank vent is blocked, the pumpout would pull a vacuum that would prevent more than a gallon or two from being pulled out. Are you sure the tank is actually refilling with water, or just has never been emptied?

[transmitterdan]

Some modern pump out systems (e.g. Edson) can create a significant vacuum. The one at our marina can suck water up at least 15 feet. If the overboard discharge is under water as most are and open then the pump out could suck seawater into the holding tank. The macerator pump will not block a reverse flow of water.

Likewise, some older poorly maintained pump outs (e.g. Pump-A-Head) often can't lift even 1 meter. In that case I agree with Peggy that the tank may not be emptied.

[edbulmer]

All hoses from macerator overboard pump have been removed and capped. So there is no way for any water to be pumped in from that. The tank is being emptied because you can hear the water coming out and then you can hear the water filling it back up. There is air coming out of the vent when it is being emptied so the vent is not blocked or plugged. Very strange.

[ranger58sb]

Originally Posted by edbulmer

All hoses from macerator overboard pump have been removed and capped. So there is no way for any water to be pumped in from that. The tank is being emptied because you can hear the water coming out and then you can hear the water filling it back up. There is air coming out of the vent when it is being emptied so the vent is not blocked or plugged. Very strange.

Can you physically see the holding tank? Can you identify which inlet or outlet port is supplying this new water? Can you trace whatever hose supplies that port back to a water source? Is it freshwater? Or sea water?

Does it only happen at one pump-out station? Or everywhere? (I can imagine a situation where head is too great for a pump-out to be effective.... so it might suck for bit, then give up. And then whatever came out, partway up the pump-out path, could run right back down into the tank again.)

I'd have thought air would going IN to the tank when you're having a pump-out.

-Chris

[Viking Sailor]

Originally Posted by edbulmer

All hoses from macerator overboard pump have been removed and capped. So there is no way for any water to be pumped in from that. The tank is being emptied because you can hear the water coming out and then you can hear the water filling it back up. There is air coming out of the vent when it is being emptied so the vent is not blocked or plugged. Very strange.

Air should be going in the vent from the outside when the tank is being emptied!

[exMaggieDrum]

Don't know if this is what is happening to you, but I thought my pumpouts at the pumpout station were doing their thing. There is a clear piece in the pumpout line so you can see the "contents" swishing by. I had no way to judge how fast or how much was being pumped so thought it was all sucked out. Not! The vent was plugged. Everything else was closed. So it sucked out as much as it could until the suction in the tank equaled the suction of the pumpout and it would stop. I just replaced the vent hose - better location to prevent blockage, bigger, and more direct to the outside.

You should have at least a 3/4" vent line - 1" better. No low spots. Don't allow the tank to overfill so stuff gets in the vent line between pumpouts.

Your problem may be something else. Good luck. I spent months rebuilding mine (because of the specific issues I have).

[hamburking]

Originally Posted by skipmac

Bottom line, I agree that Dan's suggestion is the first place to start. Check the vent hose to the holding tank to see if it's clogged up. Don't know if they have them in Canada but in the SE USA there is a kind of wasp called a dirt dauber that makes a nest of mud likes to use little holes like that for the nest.

Here on the great lakes (canada) we have no shortage of spiders, wasps, and various bugs that like to make narrow hoses and dark corners their home. One spring I pulled a massive wasps nest out of my hanging locker. Another time, my atomic 4 failed while underway due to a spider nest in the fuel tank vent. I've also had old hoses decay and flatten (especially at a sharp corner) causing them to block.

On my current boat, there is a leak in the fresh (drinking) water system. The water lines are so hard to get to, that I've just abandoned the system and use bottled water instead. To get at the leak, I'd have to tear apart most of the vee berth.

[skipmac]

Originally Posted by hamburking

On my current boat, there is a leak in the fresh (drinking) water system. The water lines are so hard to get to, that I've just abandoned the system and use bottled water instead. To get at the leak, I'd have to tear apart most of the vee berth.

I can relate. If I ever have a problem with my fresh water tank it's glassed in under the floor in the main cabin. I would have to take most of the boat apart to get to it. Cross my fingers that never happens.