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Old 19-08-2011, 02:04   #61
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Re: What Size Holding Tank? (Merged)

Mine is pretty small, around 20 liters I'd guess, it has a three way valve, one position to direct dump to the sea, one position to discharge to the tank, and a mid position to allow the toilet pump to pressure the tank to discharge it to the sea. Up to now I've either pumped out in marinas (all have pump out vacuum pumps), or discharge well offshore. For long-term living with no pump-out facility it would be mighty small.

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Old 19-08-2011, 08:19   #62
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Re: What Size Holding Tank? (Merged)

5 liters/flush??? That's more than twice what you should need! The average flush water volume that any manual marine toilet that's working anywhere NEAR factory spec should need is only about TWO liters...and you can even reduce that by learning to use the dry mode to do more than just pump the last of the water out of the bowl.

When was the last time you replaced the joker valve(s) in the toilet(s)? If you're wondering why I asking, this should explain it...and why any toilet might actually need 5 liters of flush water:


Most people think that the only thing the joker valve does is acts as a check valve to stop backflow from returning to the toilet or odor from the tank from escaping through the toilet. But that's not a joker valve's most important fact, the joker valve is THE single most important replaceable part in a manual toilet.

Here’s how the discharge half of the pump works: On the upstroke of the piston, a vacuum is created in the area beneath the piston. This causes the joker valve to close tightly, and the flapper valve beneath the pump to open, allowing some of the contents of the toilet bowl to be drawn into the bottom half of the pump. Then, on the down stroke of the piston, the flapper valve is slammed shut, and the effluent is forced out of the bottom of the pump, through the joker valve, and off down the line. But when the joker valve becomes worn and/or there's a buildup of sea water minerals on it, it can no longer seal tightly on the upstroke of the piston...less vacuum is generated when you pump it. And as it becomes more worn there's less and less vacuum, till finally the bowl contents simply move up and down a bit, but don't go anywhere. Sometimes the flapper valve needs to be replaced too, which is why toilets should also be rebuilt at least every 5-6 years as PREVENTIVE MAINTENANCE.

You prob'ly won't notice the loss of efficiency at first because it's so gradual...same as we don't see that we've gotten a little older than we were yesterday when we look in the mirror each morning. But I guarantee you that if it's been two years or longer since you replaced the joker valve, you need to pump the toilet at least 50% more times to move the bowl contents to the tank or all the way out the thru-hull....IF they're getting there at all any more.

Marine toilets have moving parts that require maintenance. PREVENTIVE maintenance is called that because it PREVENTS problems that have to be fixed. You get to do PREVENTIVE maintenance on YOUR terms, when it's convenient for YOU...unlike repairs, which NEVER are needed at a convenient time.

As for what size holding tank...there really is no right answer. Boat size provides a "rule of thumb" when it comes to trying to come up with an adequate size tank for the number people the boat can carry. But just 'cuz a boat CAN "sleep 6," how often does it have more than 4 or even just two aboard for more than a day or evening? A tank that allows for max capacity would turn most boats into honey wagons!

So what it almost always comes down to is the size of the space that's available in a location that works--where it can be vented to keep it aerobic and with simple straightforward plumbing.
© 2016 Peggie Hall
Specializing in marine sanitation since 1987
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Old 09-11-2013, 12:25   #63
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Re: What Size Holding Tank? (Merged)

The extenuating circumstance in this case is, (there's alway at least one on a boat issue) that you may have to empty it by removal or hand. In such a case a smaller under 20 gal will enable you to lift it. Find a landlubber's sewer pipe anywhere on land you can and pour it out down the clean out. If you have to, take the darn tank in the house and pour it down the toilet. There are RV pump outs too. Rinsing is touchy but name anything about a marine head that isn't.
This method requires special feed and disconnects and you can buy them in plastic that fits standard pipe thread. They are called 'cam and grove' fitting like they use for fire hose. Be sure to buy the caps as well and if you are really sensitive buy a fitting and a cap for the pipe while you are away emptying it.
The tank can be secured by several types of releasing straps. (NOTE: In a smaller than 32' boat storage above water line is a rock and rollers dream). I like a child's push button three way seat belt, (thrown out with car seats everyday). You will need to strap a carry handle on it too. The tank could of course have the option of a pump out on deck for when it's convenient. It's my guess if you get used to it on a dolly, you will easily carry the tank to a near by pump out. The coasties are looking for heads that directly discharge. Even more so than your delinquent registration papers. Because it's all about revenue stream. Fact is, cities pump billions of gallons of sewage into the ocean daily. Don't be a scoff law. Deposit it where the bureaucrats say. It helps with your digestion

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