Flushing with fresh water

[farotherside]

hey,

I have a Groco Model-K head. I just replaced all the effluent hoses for the first time in a few years, and they were pretty gunked up with calcium, so I want to change the flushing water from saltwater to fresh.

I've removed the through-hull near the head and glassed over the hole, and run the hoses through the boat towards the tanks, but then last night I woke up in the middle of the night with a strange thought and now it's driving me nuts.

when I rebuild the head last week, I replaced all of the seals and flappers and rings and such using a rebuild kit. awful job, but at least it's done for another few years. one thing that stuck out was that the flapper preventing backflow from the toilet into the seawater/flushing water line was destroyed and leaking badly. anything left in the bowl was leaking out and down the feed line, which I discovered the hard way after I removed the through-hull but didn't plug up the hose, and the contents of the bowl leaked out into the bilge. :/

my Q: if it's possible (regardless of whether or not it's normal) for effluent to leak into the flush feed hose, is it possible for bacteria from the toilet to enter the feed hose and make its way up to contaminate my water tanks?

my second Q: is there a good way to mitigate this risk? I was thinking maybe a check valve or a vented loop, but I'm already asking the head to flush with a 1/2" feedline instead of the 3/4" or 1" that it really wants, I'm worried about throughput.

any input helps!

[peghall]

my Q: if it's possible (regardless of whether or not it's normal) for effluent to leak into the flush feed hose, is it possible for bacteria from the toilet to enter the feed hose and make its way up to contaminate my water tanks?

Yes. And the risk is even greater for Groco Model K toilets that are at least 15 years old, because that's about when the piston bore wears beyond spec and the rings allow pressure to create "blow by," causing the toilet to begin to recirculate black water. The piston is double action pumping black water on the up stroke and raw water to the bowl on the down stroke.

The rebuild kit won't fix this. You can send the pump back to Grodo to replace the bore housing but that's expensive...not as expensive as a new Model K, but more that you'll want to spend.

But whether your toilet is a Model K or not, bacteria can migrate from the toilet bowl into the fresh water plumbing, which is why every toilet mfr warns against connecting any sea water toilet to the fresh water plumbing.

my second Q: is there a good way to mitigate this risk? I was thinking maybe a check valve or a vented loop, but I'm already asking the head to flush with a 1/2" feedline instead of the 3/4" or 1" that it really wants, I'm worried about throughput.

With the exception of the Raritan Fresh Head FRESH_HEAD Promo Sheet , which is designed to use pressurized flush water from the potable water supply, there is no way to safely connect any manual toilet to the potable water supply. Your only choice would be to install a flush water tank that's totally separate, including fill and vent, from the boat's fresh water system.

If your main objective is to prevent salt and sea water mineral buildup in the hoses, there's an easy way: flush a cupful of undiluted distilled white vinegar all the way through the system once a week...followed by a quart or two of clean FRESH water after about 45 minutes.

However, there is a another way that works on most boats: tee your toilet intake line into your head sink drain line. The tee needs to be below waterline as close to the seacock as possible. This allows you to flush normally using sea water, but also provide a safe source of fresh water to rinse it out of the ENTIRE system before the boat will sit or even daily if you're a liveaboard...simply close the sink drain seacock, fill the sink with clean fresh water (don't even THINK of using gray water to flush!), flush the toilet. Because the seacock is closed, the toilet will pull the water out of the sink...rinsing out the intake line, the pump, the channel in the rim of the bowl and the discharge line. You can even add vinegar to the water in the sink. For this work, the toilet and the head sink have to be on the same side of the keel and the sink to drain thru-hull has to be below waterline. If the sink drains above waterline, unless the toilet intake thru-hull is too far from the head, just reverse the connection--tee the sink drain into the toilet intake line.

[44'cruisingcat]

A year or so back, I removed one of our toilet outlet hoses to check it out. After 6 years full-time liveaboard it HAD to be all calcified up, right?


But it wasn't. There was only a tiny film on the inside of the hose.


why? I believe it's because we flush the toilet properly. We give it a good long flush, every time. Calcification will only happen if urine is left sitting in the hoses. A good long flush will get rid of the urine.


You won't block the toilet with water.

[Large Luke]

I have a question. Why couldn't we just take a cup or so of water from the sink and pour it into the head. Do our business and just flush that, and not even pump any seawater water into the head? Is this a reasonable option?

[jamhass]

Just adding water to the bowl works, mostly. But eventually the water left in the rim will foul and make smells, especially if sea water. We went the T in the sink drain method and are very happy with it. We kept the sea water flush option for at sea direct discharge flushing.

[peghall]

You could...in fact, some people just keep the intake seacock closed and use the shower head to supply flush water. But that's not particularly good for the pump because what's in the bowl only goes out the bottom of the pump...and they're designed for water to go through the whole pump. Teeing into the sink drain would be easier than a cup...just run water down the sink and flush. That would require keeping the sink drain seacock closed except when using the sink, but unless it's in a really awkward location, not that big a deal for the few times you'd need the sink in a day.

Keep in mind too whether you carry enough fresh water to spare for toilet flushing. The average adult uses the toilet 5x/24 hours, average flush needs about .5 liter flush water. That's about 3 gal/day/person, which can add up.

[bensolomon]

On my 37.5 Hunter Legend, I use freshwater. I simply take the shower fixture and turn on the sink and fill the manual jabsco toilet and then flush. I always keep a little bit of bleach in my fresh water and this has kept the stink away completely. By the way, my boat is 27 years old. I keep the intake Seacock closed and only use sea water if we're out in the ocean. My typical cruising ground is Chesapeake Bay.

[tkeithlu]

I plumbed our two electric Jabscos to the pressurized freshwater supply, and quickly discovered that the pumps pass water while not operating and flood the bowl. The answer was a spring loaded valve next to the DC power switch. Pull down the valve chain, feeding water as needed, while holding the switch "on" until everything is flushed and some clean water is left in the bowl. It has no way of back feeding into the tank, because 35 psi sits on the back side of the valve and the hose from the valve to the bowl empties. I blocked off and bypassed the usual water supply pump. It's more complicated to operate, but no smells and nothing growing.

[sailortype]

I do like the idea of fewer holes in my boat. I'm also glad this came up now because I was thinking of using one large seacock and a large filter unit and multiple tees and inline shut-offs as a source of water to all faucets, head, engine etc. Clearly head plumbing should be kept separate.
But- if the toilet intake was teed into the drain just above the seacock and the drain is a short run, would you not have to use a plug in the sink when flushing the head to avoid sucking air..?

[farotherside]

damn. looks like I'm re-installing that through hull fitting.

good to know, at least I didn't contaminate my tanks and get myself or my guests sick! thanks Peggie, your posts are always well written and extremely helpful - this isn't the first time you've helped me with my Model K.

[Captndave1]

I placed an under sink water filter in line with the head intake and replaced the filter element with a "2000 flushes" toilet bowl freshener. The chlorine in the "2000 flushes" kills the bacteria and sea life in the intake water and keeps the bowl fresh and tidy. Result, no stink, ever.

[sailortype]

seems to me you might also be killing the 'good bacteria' in the holding tank which is degrading the waste. Hopefully Peggy might comment on that :-)

[Captndave1]

"2000 flushes" is approved for septic tanks which is the land version of a holding tank. I have had no problems with holding tank function. I also put a tablespoon full of "ridex" in the holding tank every few months. My friends tell me i have the best smelling boat around.

[gts1544]

ONE MAN'S SALT WATER TECHNIQUE WITH OVERBOARD DISCHARGE INTO OFFSHORE WATERS - Open the seacocks - Ensure that there some water in the bowl - Take care of "business" - Flush the "business" out of the bowl using DRY BOWL - Switch to WET BOWL and pump 15 full strokes - Close both seacocks. This usually ensures that the exhaust lines are clear of any "business". ALLOW NOTHING NON-ORGANIC!

Periodically use a little Clorox, followed by a little vinegar, allowing each to sit for a short while, followed by a small amount of vegetable oil to lube the pump, rotating the handle while pumping. We have been basically trouble free. George

[peghall]

But- if the toilet intake was teed into the drain just above the seacock and the drain is a short run, would you not have to use a plug in the sink when flushing the head to avoid sucking air..?

Some boats seem to need a plug, others don't. Rubber sink drain plugs are readily available and very inexpensive at any hardware store or even Walmart, so it's not a big deal if you do.

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