PS Advisor August 2018 Issue

Cure for Holding Tank Clog

Any suggestions about what to do with a clogged holding tank? Iíve isolated the clog to between the base of the tank and the elbow after the toilet macerator. Iíve been treating the system with straight vinegar down the pumpout tube and thru the bowl to no avail.

Anonymous Sailor

via PS Online

In our recent toilet paper test Scott Rapid Dissolve single ply lived up to its name (see "Best Marine Toilet Papers," PS October 2016.) It dissolved without collecting at or clogging joker valves (at left).

From the sounds of it, the vinegar is not reaching the clog site. Chemical drain cleaners can reduce build-up and can help on a slow drain, but once the blockage is complete, they canít reach the problem. Much of our advice for cleaning a holding tank apply to your situation (see ďPS Advisor: Cleaning the Holding Tank,Ē PS November 2015).

Remember, vinegar is a weak acid, barely able to dissolve lime scale and will have no effect on paper solids. Drain cleaners are used for paper, fats, and organics. These are strong bases (the opposite of acid), but we do not recommend these for marine systems because of the harm they can cause.

You could try stronger chemicals, but since they wonít reach the clog site anyway, they would only increase the risk of equipment damage or personal injury. A physical cleaning described in the 2015 PS Advisor report is going to be your best approach.

The first thing to try is reverse pressure. This will only work if the macerator pump does not include a check valve; diaphragm pumps contain check valves, centrifugal pumps generally do not (see ďPump Details, the Modern Macerator,Ē PS November 2011).

First, put your own high-pressure nozzle on the end of the washout hose. (This is to avoid contamination of the hose end, which is often used for water fill.) Fit the hose into the pumpout fitting and seal the gap with a wet rag and your hand. Let the water blast for 10-30 seconds, and then gradually release the seal. Donít do this suddenly or you could get a mess in your face.

If this has no effect, try an adapter that will get a tighter seal. The pumpout is usually threaded 1 1/2-inch FPT threads. With an assortment of fittings you should be able to attach a male fitting to match and apply greater pressure. Be careful as you increase pressure. Although your discharge hose and fittings should be rated to at least 100 psi and dockside hose pressure is usually regulated to just 40 to 50 psi, your system might have some weak and aged components that might fail.

If a high pressure blast doesnít work, try suction. Remove the fill fitting at the tank and construct a wand that fits down the hole, and suck the tank clean.

Once the holding tank is empty, take the plumbing apart and clean it according to the methods described in the 2015 PS Advisor. Sometimes the clog is a mass of paper that has collected against the outlet. If your tank has an access port, you can blast that area with a hose and pump out the buildup.

In the future, the best practice is to blast the hose down the pump-out fitting for at least 30 seconds after every pumpout, and then pump that out too. Shoot some water in the vent while you are at it. If you must use the dock-supplied nozzle fitting for this, avoid contact with your pumpout outlet and sanitize it with a chlorine wipe down. The last thing you want is for someone to fill their water tank with a contaminated hose end.

Never flush anything other than waste and dissolving single-ply toilet paper (no 2-ply, no facial tissues), and use plentiful water with every flush. These are vital preventative steps.

If further disassembly is required, keep your sense of humor. Like changing diapers, itís just poop.

Comments (9)

In the been-there-done-that category, we had the same problem when we purchased our "new" boat. We have a Bavaria Ocean 38 with a very simply, robust waste holding system. It starts with a PHII manual head, approximately 2 feet later and under the head sink is a "Y" diverter and maybe 15 feet later, the sanitation hose drains into the top of the holding tank. The sanitation hose appears to gently weave under the floor and low into the engine room space, up the bulkhead about five feet (or four feet above the rim of the toilet meaning inspect and replace joker valve regularly) where it makes a sharp 90 degree turn into the top of the stainless steel, 15 gallon holding tank. Nice design, but clogged fast.

Scared, we tried everything to loosen the PO's legacy clog, having ourselves never flushed "solids" or even paper into it. To his credit, the previous owner warned us of "calcification issues". Whatever we did only made matters worse to the point that the waste hose was holding pressure from the manual head's hand pump; impressive but bad.

We used vinegar, flexed the hose everywhere we could, drained the holding tank, used the Y diverter to ease the pressure and finally loosened the two hose clamps at the top of the tank. While opened, we covered the holding tank inlet with a sandwich bag and rubberband and attempted to straighten out the tight bend at the top of the hose. No luck. With a flashlight, we peered down the hose and saw a white concrete-like clog three inches away. Calcification? No; too much toilet paper turned to plaster. We went to Home Depot and bought a couple of tiolet snakes. The little one had a hooked corkscrew end that did the trick in under a minute. Then for good measure we ran a proper snake all the way back to the Y valve and encountered no resistance.

Lesson learned, look for and question the most obvious point of flow restriction for obstruction, to avoid future clogs, use plenty of water to send the waste down the line, use less paper than one would at home, and an ounce of prevention, like snaking the whole line when the opportunity presented itself, is a time and effort well spent.

Posted by: SY-Zephyrus | August 26, 2018 2:19 PM    Report this comment

Our Hunter had an issue regarding holding tank capacity. After several gyrations and removing the tank it was determined that the extraction tube made of aluminum had developed a hole 2/3's from the bottom reducing the capacity from 38 to 15 gallons. We probably could have had the pickup tube sleeved but elected to have a new tank built out of polypropylene rather than deal with the same problem in the future. Contact Triple M Plastics in West Kennebunkport, Maine for replacement tanks to your specs.

Posted by: hunter | August 24, 2018 6:18 PM    Report this comment

Be careful about pushing water back/down a holding tank air vent [hose]. Many have carbon granule filters that will get clogged/damaged by the water - and the water that doesn't drain from the hose will actually block the vent ...

Posted by: chrisc | August 19, 2018 9:49 AM    Report this comment

As to clearing the clog , is the holding tank vent clear? if so it's possible the feed hose out of the macerator and into the holding tank will need to be completely taken off and manually cleared. this is an unpleasant but easy job for which the yard will charge huge amounts of money.

As to a permanent solution, I write as an owner of 3 sailboats and 2 RVs who each had macerators. We keep a covered paper waste bin next to the toilet. The RULE was: ALL paper products go into the waste can, not the head. (This is a difficult concept to explain to certain young guests, especially teenage females. ) Operating under this rule, we've never had a macerator problem or a clog.

Posted by: MitchM | August 13, 2018 6:06 AM    Report this comment

Use regular toilet paper. Fold used part in against itself. Deposit in ziploc bag. Seal it up. Dispose of ziploc bag when full. Not as yucky as it sounds. Never put any paper in your marine head and you will eliminate about 90% of problems with this essential boat system.

Posted by: rersk | August 12, 2018 7:55 PM    Report this comment

Put half a cup of baking soda in the deck pump out pipe and pour one or two cups of boiling vinegar.
Worked for me

Posted by: Skipper | August 12, 2018 5:07 PM    Report this comment

Put half a cup of baking soda in the deck pump out pipe and pour one or two cups of boiling vinegar.
Worked for me

Posted by: Skipper | August 12, 2018 5:07 PM    Report this comment

I've recently been resolving waste system issues. Here's a couple of thoughts. We found that the air vent to one of our holding tanks had a total obstruction. Not the thru hull opening above the water line and not the 1" hose from the tank to it. It was the 1" right angle bronze fitting from the top of the tank to the hose. It was totally calcified. Not room for a hair. We removed it gently from the top of the tank (in the typically inaccessible location) and cleaned it physically with a flat blade screw driver. Then we soaked it in vinegar until it looked new and reinstalled it. The diagnosis of an airway problem was made by the fellow vacuuming out the tank at a fuel dock. His hose started burping and wreching --> "You've got an airway obstruction." Being a trained veterinary anesthesiologist this seemed quite appropriate!

Next a lesson in impellers. They needed to be cared for. Those at the toilets are easy. Avoid paper, use vinegar routinely and use clean oil (canola/rapeseed oil, e.g., a cup a month. Impellers in macerators between the holding tank and thruhull require a bit more thought. When flushing any waste circuits with vinegar flush just enough for the vinegar to sit in the hoses for 12-24 hours. Then flush out. With holding tank macerators it's wise to be near them when duscharging and listen or feel for what's happening. If you're up in the cockpit with the engine and radio going you can't hear the macerator. Once the tank is emptied the propellor in a typical Xylem/Jabsco unit becomes free of any flow --> a high-pitched whir. Turn it off because it becomes rubber on the impeller housing which wears the edges, overheats and flips the circuit breaker. When our holding tanks are empty, once a month we flush 1-2 toilet bowls of clean water into the tank. Adding a cup of oil to the toilet bowl when you're emptying the holding tank of this "cleansing" water will help protect this impeller.

Posted by: ChuckCohen | August 12, 2018 11:55 AM    Report this comment

We found that the seawater urine problems are cured by safe use of a super product, recommended by Peggy Hall, the Head Mistress! It is a Raritan product called CH. Initials easy to remember by the name CLEANS HOSES! Will safely dissolve the calcium deposits and makes them like new. A repairer of the Raritan LectraSan advised us that if you use the CH you will never have to clean your hoses again. It is safe for all products in the lines and not harmful to humans when used as recommended. We have found it regularly at discount at Defender. Ed and Sue Kelly, on USSV ANGEL LOUISE, lying Rockland, Maine (full time cruiser/explorers having visited 49 countries on shores of 5 continents)

Posted by: | August 2, 2018 3:18 PM    Report this comment

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