Clogged holding tank

[Mrkva]

Hello everyone,

last autumn I've bought a boat, and unfortunately had not enough time to investigate all the possible systems on board - I was expecting a head being plumbed directly overboard, but it was not. This year, after I've cleaned up all the stuff that was stored in the head and cockpit locker, I found a stainless steel holding tank, with a manual overboard pumpout (using diaphragm pump, looks almost the same as a manual bilge pump).

The problem is when I move the pump handle up, I feel like I'm pulling a vacuum (the way handle feels and I hear air hissing). So I suspected gunk on the bottom of the tank (partially) solidified, so I flushed a cupful of laundry detergent with another cup of water softener, and left it sit for a day. This did not help, and few minutes after flushing there was huge smelly backflow to the toilet (just gasses and what water was left in the pipe).

I found a clogged vent through hull, but unless it's clogged at the tank simultaneously, it's not the cause of inability to pump out. I'll be sailing next week, so I guess there's a chance some wave and heel action will dislodge the mess, but I'm not holding my breath.

Now, the problem is the season is almost over. The tank (together with outlets, hoses, pump) is almost inaccessible and has no inspection hatch or deck pumpout, and I might end up having to "winterize" holding tank full of who-knows-what, and deal with the contents in the spring. Any suggestions how to do that? Temepratures here are not that cold (minimum is around -2 or -3C), so I guess pumping to it a few cups of antifreeze might help? I really don't want to end up with the tank contents in the bilge.

[LittleWing77]

Peggie?

This is your area of expertise...

(If you don't get a reply, PM Peggie Hall, who is a member of the Forum and sounds as if you need a copy of her book as an onboard resource...) https://www.amazon.com/New-Get-Rid-B...8702143&sr=8-1

LittleWing77

[Bill O]

Would take the vent hose off at the tank and see if that helps.

Do you have a pump out fitting on the deck? Have you tried to clean out your tank this way? If this works, then flush several times w/a hose then pump out. This should get the majority of the crude out.

Also could take it out for a brisk sail in a little chop and shake up the tank contents. This will loosen things up then get the pump out. Before things settle, pump it out.

Another thing to check in your newish to you boat. If you have a deck pump out and a separate dump pump, then you may have a directional y valve in the system. Make certain this is correctly positioned for the pump to work otherwise it could do the "vacuum" as you described. (it maybe set/positioned for the deck pump out to work).

[Nicholson58]

The air hissing sounds like there could be a bad diaphragm in the pump. This is often a bilge pump as you noticed. Parts are available for all but the oldest pumps. Possibly a Whale Gusher.

Is there a deck pump out fitting as well? If so, go to the pump station.

[tkeithlu]

While waiting for Peggie, let's think about the hissing sound. That's likely air leaking inward between the blockage and the pump, unless the one-way valve on the down side of the pump chamber has failed to seal. Where is the hissing coming from?

Does the tank itself have a suction in it when you lift the lever? You might determine that with a hand on the side of the tank or visibly if the tank "oil cans."

Is the vent clear all the way to the tank? Can you run a wire down it?

We're getting to the location of the clog.

Once you've narrowed down the location, it may get messy, because you'll have to disassemble to mechanically break it up, unless Peggie can suggest another way.

Chemical treatment of clogs really doesn't work well if the clog is complete, because the chemical can only get to one surface to disolve stuff.

If it really is clogged between the pump and the tank, and with the vent clear, some air pressure, as in an air gun in the end of the hose to the tank, with a rag around it to keep most of the air in, might blow the clog back into the tank where it could be broken up.

Good luck. Hopefully Peggie will step forward. Get your gloves and face shield ready.

[GILow]

Originally Posted by Mrkva

...
The problem is when I move the pump handle up, I feel like I'm pulling a vacuum...

Sorry to ask what may be an obvious question, but have you confirmed there is not a shutoff cock between the pump and the tank?

I ask because I set mine up with one so that I could choose either deck pumpout or manual pumpout from the same pickup tube. I needed to be able to isolate the pump from the pickup tube if pumping out from the deck fitting, and likewise isolate the deck fitting when using the manual pump out.

I don't think my setup would be all that unusual.

Matt

Edit: I just read the OP properly, ok, no deck pumpout fitting, but there may still be a shutoff cock. I know I'd want one just to be able to lock down the holding tank if maintaining the pump.

[gonesail]

it might be good idea to know when the last time it was actually emptied overboard or otherwise. also you did not say if there was an inspection port. i think you need to be able to look at the interior of the tank.

[ggray]

If the pump is indeed just a bilge pump, before you spend any money on it, look into a proper black water pump:

https://www.whalepumps.com/marine/pr...anitation-Pump

These are sealed up against odors. Replacing a manual bilge pump installed for this purpose on our boat with one of these made a big difference in odor.

[Nicholson58]

If there is an inspection port and you determine there is a brick inside then perhaps a power washer would break it up. Lucky you, have fun and wear your hazmat suit.

[Bill O]

Originally Posted by Nicholson58

If there is an inspection port and you determine there is a brick inside then perhaps a power washer would break it up. Lucky you, have fun and wear your hazmat suit.

I did reread the OP's post and said there was no inspection port nor a deck pump out fitting.

[Nicholson58]

Originally Posted by Bill O

I did reread the OP's post and he said there was no inspection port nor a deck pump out fitting.

Thanks Bill. He could break a line to run the wand inside. Hoses are probably due for replacement anyway. Doing ours this year assuming we are allowed back into Antigua. 35 feet of Raritan Saniflex on order.

[Bill O]

Originally Posted by Nicholson58

Thanks Bill. He could break a line to run the wand inside. Hoses are probably due for replacement anyway. Doing ours this year assuming we are allowed back into Antigua. 35 feet of Raritan Saniflex on order.

Just a suggestion in your hose replacement, is to use as much sched. 40 PVC as you can. No smell permeation and much cheaper.

We did ours a couple of years ago and works well. Easy to install the pvc when we replaced our hoses. Except for a few tighter turns, the rest is all pvc.

[Mrkva]

Yeah, there's no deck pump-out or inspection port. There isn't a valve between tank and pump - just between pump and thru-hull; there's no need - the pump is positioned slightly above the tank.
Replacing hoses is on my short-term ToDo list and actually the thing that started the whole thing.


I went rodding in my dinghy today. Lot of debris fallen out, but I cannot get past ~30cm in. Using camera on a stick from the inside of the locker I can see a bend in approximately the area, but I cannot reach it without removing few screwed-on parts to check it closer.



Also I think I should be able to pump at least once or twice before the vacuum will be strong enough to prevent me from pumping further?

[Montanan]

Peggy is the expert within this forum, her guidance is ever so seaworthy.

If the boat does not have a deck pump out fitting, it should have one installed, else one will need to voyage to a location that allows for discharge into the waterways, everytime the holding tank becomes full which may be but a few miles offshore or a longways out of a bay. And in some jurisdictions / marinas, one will have to seal the direct discharge route, e.g.,, by sealing the Y valve so it diverts to the holding tank, closing the head so as to not use such toilet. etc.

Good luck.

[peghall]

I found a clogged vent through hull, but unless it's clogged at the tank simultaneously, it's not the cause of inability to pump out.

Sorry, but it most certainly can be, and if cleaning out the thru-hull didn't relieve the pressure, almost certainly IS the problem...'cuz it's highly unlikely that sludge has built up in the tank high enough to block the discharge fitting.

Start by cleaning out the thru-hull...use a screwdriver blade, ice pick--whatever works. If the thru-hull has a screen, knock it out...screens causes 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 that end out. Scrape out that end of the vent line and the vent fitting on the tank...reconnect the vent line.

Without a deck pumpout (which, btw, US marine sanitation laws require), I dunno how you'll be able to relieve the pressure before removing the vent line from the tank. Air in a seriously pressurized tank will try to escape wherever it can, usually back through the toilet or maybe even that's what's causing the hissing in your diaphragm pump. I wouldn't try disconnecting the hose from the tank to it or taking it apart to find out! If you can wait 24-48 hours before doing anything more--and without using the toilet!!!, there's a good chance that most or even all of the pressure has been relieved, at least enough to remove the vent line from the tank if you position a plastic waste basket liner to catch the spill.

Don't try adding antifreeze or anything else to the tank...pumping the toilet will only increase the pressure in the tank.

Also I think I should be able to pump at least once or twice before the vacuum will be strong enough to prevent me from pumping further?

Don't do that either...you'll only prevent the pressure from dissipating.

--Peggie