Is There A Rule About

[peghall]

Amen! That's one of those ideas that sounds good, but only someone who's never tried it would recommend it. Although you could burst the tank, tank contents under pressure will follow the "line of least resistance" to escape, and that's through the toilet. You're more likely to get a face full of sewage when it erupts while you're pumping it. I've seen it turn a joker valve inside out.

Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

[w1651]

okay scrap the toilet pump idea and go with vacume by way of a diaphram pump just before the sea cock then.

[reed1v]

For our old ws43 we installed old fashioned plastic water tank(new one of course) above the head. The head was set on top of a holding tank. Other than having to open the head/holding tank hole(lever), visitors could use the facilities like shore side folks do. Pull the chain. The holding tank had two outlets: marina pumpout side and ocean dump side. Ocean dump side was just below the water line. If you wanted to empty the tank at sea(horrors), just open the ocean outlet(2") and let gravity and the movement of the boat suck the tank almost dry. No muss, no fuss, no odors(except if you were a fish), and no worries about the toilet flooding the boat.

We used fresh water to fill the top water tank to avoid the smell of stagnant sea water. 3 gallons capacity, good for two flushes. Filled with an additional faucet attachment to the regular cold water line. Vent was routed through the hull at almost deck level. Outside of manually turning on and off the refill water, was a no brainer system.

[leftbrainstuff]

Head pressure is proportional to height above sea level. Place it as high as you can. Minimising bends, restrictions and loops will all help discharge flow.

Dont plan on any venturi effect addressing lack of flow or head pressure.

I dont allow any PVC pipe, assuming you're referring to domestic pipe, on our boat.

Also draining to water is a non no in most areas.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[davewtsnape]

20 cm above the waterline I believe. Look at the tektanks website or similar

[Viking Sailor]

Originally Posted by Rapanui

I would be extremely careful about using the head pump or any other pump to clear a holding tank blockage. Tanks are not designed to take any significant pressure and can rupture at fairly low pressure. The consequences of a shower of s**t on the inside of a boat are too awful to risk.
I met a Swedish cat owner where just such an event occurred. Their boat was fitted with the carpet type sidelining and that had to be totally removed. The boat still smelled after some time.

Originally Posted by peghall

Amen! That's one of those ideas that sounds good, but only someone who's never tried it would recommend it. Although you could burst the tank, tank contents under pressure will follow the "line of least resistance" to escape, and that's through the toilet. You're more likely to get a face full of sewage when it erupts while you're pumping it. I've seen it turn a joker valve inside out.

Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

Gee guys - I must be one of the luckiest SOB's on this planet! I have owned, lived aboard, and sailed Feeling Good for 38 years. And, for at least 35 of those years the head/holding tank has been configured as above. In all that time I have cleared discharge and vent blockages without blowing up the tank, bursting a hose, popping off a hose, or generating a fountain of waste. So, although I am on my third head, and I know that you mean well, I will continue to use my flawed system trusting to luck that I don't end up knee deep in my own waste.

[Rustic Charm]

I installed what your wanting to do.

Put the tank as high on the wall above water line as you can get. Anything above waterline will result in a discharge, but higher the faster the discharge.

I have a head sink below the tank which discharges into the same seacock. This resulted in Blackwater coming up into the sink if the seacock was off. So I had to install a separate valve under the sink to turn the sink off when using the holding tank and when heeled.

Don't use normal grade pvc. Use 'steam pipe' in plastic. Much tougher. Make sure you use both the appropriate steam pipe primer and glue. I've had no problem with steam pipe.

And I have an electric macerator which means no blockages, ever.

I have an option for pump out on deck too. No separate valve was required for this.

[peghall]

Someone on another site has a catch phrase pinned to his posts that seems to sum things up pretty well here: "There's a right way, a wrong way and what some guy gets away with."

Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

[mitiempo]

Originally Posted by w1651

okay scrap the toilet pump idea and go with vacume by way of a diaphram pump just before the sea cock then.

The tank will not self drain through a diaphram pump.

If the tank bottom is above the waterline a ways gravity works well. The tank should have a valve at the bottom as well as the seacock at the hull. This way after emptying you close the valve at the tank bottom and leave the seacock open so movement through the water cleans out the pipe. A good idea as well is to make sure the deck pumpout fitting is in line with the lower outlet - if there is a clog you can push a broom handle through to clear it.

It is by far the simplest of systems with virtually nothing to fail.