Cleaning Out Gray Water Tanks

[accomplice]

Dockhead, I'm thinking of adding a grey-water tank like you describe. I've already purchased it, along with pump, but haven't yet installed. Currently the galley sink drains directly overboard through one-way valve -- when it drains at all. Food particles/oil/grease accumulate in the drain line between the hull and the sink. Your post has me wondering, though, if I might not be better off just plunging the sink when it clogs, instead of having to clean out the (proposed new) grey water tank. Thoughts?
Thanks.

[IdoraKeeper]

Originally Posted by Dockhead

But they say that they are for both gray and black water tanks? False advertising?

Well, your simplest easiest solution is similar to what i have been doing -- bail the tanks out into a bucket, and scrub clean. I wouldn't use a pressure washer, as that would put all the stinky carp into the air! It's such a disgusting job, I was hoping for some other method. LIke healthy bacteria or something else to dissolve the carp which collects there so it goes overboard.

There are people in Michigan and Illinois who would like to dissolve carp but you live in a civilized society that would object to dissolving fish. Before this cruising season you were concerned with excess carp on your aft deck. You installed davits and gave up on the carp on the aft deck we were relieved on behalf of the fish. Now your talking about removing the davits and abusing fish in the interior of the boat. Far better to rip out the grey water tank(s) and eliminate the mess than to take it out on the fish. By the way, you have an ingenious crew if they figured out a way to stuff carp into the grey water system!

[rwidman]

Originally Posted by accomplice

Dockhead, I'm thinking of adding a grey-water tank like you describe. I've already purchased it, along with pump, but haven't yet installed. Currently the galley sink drains directly overboard through one-way valve -- when it drains at all. ........

Why is there a "one way valve" (I assume a check valve)? Remove the check valve, make sure the drain hose is as short and straight as possible with no loops and it should drain effectively.

Adding a sump and a pump is only making something simple (gravity) into something complex.

[accomplice]

Originally Posted by rwidman

Why is there a "one way valve" (I assume a check valve)? Remove the check valve, make sure the drain hose is as short and straight as possible with no loops and it should drain effectively.

Adding a sump and a pump is only making something simple (gravity) into something complex.

Yes, one-way valve = check valve. I replaced the check valve thinking the old one must've been crudded up (carped?), but it wasn't too bad. The hose is fairly short -- maybe 5-6 feet with a large radius bend in the hose and a 90 degree at the seacock. Practical considerations keep it from being any shorter. I estimate the hose to hold at least a half of gallon of water below the waterline. I believe the primary issue is that the waterline is only several inches below the bottom of the sink. The oil/grease/small-floating-food debris sits at the top of that pipe, above the waterline. I'd love to just install a pump in-line, but the discharge hose then really should be routed through a vented loop above the waterline in the event the pump fails. Hence my plan to route the sink discharge to a holding tank, dump a shower drain into the same tank, and use the vented-loop/discharge from the shower drain. It is quite a bit of work, though -- and if I'm facing having regular grey-water-tank cleanout problems, I might just stay with the problem I have now instead.

[ranger58sb]

Originally Posted by accomplice

Currently the galley sink drains directly overboard through one-way valve -- when it drains at all. Food particles/oil/grease accumulate in the drain line between the hull and the sink. Your post has me wondering, though, if I might not be better off just plunging the sink when it clogs, instead of having to clean out the (proposed new) grey water tank.

FWIW...

Both our sinks drain directly overboard, via outlets above the waterline.

Neither drain hose has a check valve, but both lines have P-traps -- which do tend to accumulate some spinach (carp?) from time to time, especially if we don't run enough fresh water through. (We understand P-traps are useful to keep odors, and/or perhaps genset fumes -- as from neighbors during a raft-up? -- out of the boat.) One of those P-traps (head sink) is very deep and sometimes slightly more odiferous, the other is seldom smelly but I think it's deeper than it needs to be to accomplish odor/fume control.

I've thought about decreasing the depth of the P-traps, and may well get around to it sometime, but in the meantime, both hoses submit to the occasional plunger treatment. That probably cost $1.98 at Home Depot, no particular additional effort required.

We do sometimes add a little CP to the drain hose, enough to keep the bit in the P-traps from getting too stagnant if we're going to be off the boat for any length of time.

I think Dockhead's situation convinces me I probably wouldn't want additional gray water sumps, if not forced to have them. Occasionally cleaning the small sump from our shower (which also captures condensate from one of the aircons) is enough for me.

-Chris

[jeepbluetj]

The solution to pollution is dilution....

RV'ers all talk about the need to keep water in the tanks, to keep the sludge in suspension. On my motorhome the grey tank is always pretty clear, because we'll flush alot of water through it via showers, etc.. (And it sloshes around while driving)

The black tank, nosomuch. Not enough water and you get a "poo pyramid" So I installed one of these:

Amazon.com: Camco 40126 Tornado Rotary Tank Rinser with Hose: Automotive

Works great, gets the gunk out of the tank when used often.

So something like this may help dockhead out of having to clean it again - just force lots of rinsing periodically. Methinks the problem with the sump is not enough water to clear out the sludge. Also may wish to move the float to keep more water in there so it sloshes around enough to help put the sludgy bits into suspension.

"The Sludgy Bits" sounds like a good name for a band.......

[Dockhead]

Originally Posted by accomplice

Dockhead, I'm thinking of adding a grey-water tank like you describe. I've already purchased it, along with pump, but haven't yet installed. Currently the galley sink drains directly overboard through one-way valve -- when it drains at all. Food particles/oil/grease accumulate in the drain line between the hull and the sink. Your post has me wondering, though, if I might not be better off just plunging the sink when it clogs, instead of having to clean out the (proposed new) grey water tank. Thoughts?
Thanks.

There are pluses and minuses of both approaches.

If your main problem is clogging, then it's not going to get better with a tank -- it will only be worse.

OTOH, the tank is very efficient and allows you to get the outlet well above the waterline.

My previous boat drained directly overboard, and I personally would not prefer to go back to that arrangement.

If you are designing a system from scratch, you should pay attention to these points:

1. Be aware that there WILL, no matter what, be food particles and decay and hence -- stench - to some extent or another. So be sure that the tank is installed just like a black water tank with a vent overboard and proper traps to your sink.

2. Try to pump it out from a sump or low point in the tank so that as much crap as possible gets pumped straight overboard. My tank fails in this regard, as it has a flat bottom and is pumped from a kind of bilge pump strainer. This leaves solds settled on the bottom, which I guess is my main problem.

3. Do have an automatic control (use a bilge pump float valve) but also have a manual override so you can pump it all the way dry.

[thinwater]

Originally Posted by rwidman

Why is there a "one way valve" (I assume a check valve)? Remove the check valve, make sure the drain hose is as short and straight as possible with no loops and it should drain effectively....

Accomplise:

I'm guessing that the one-way valve is to keep water out when heeled. Check before you remove it.

---

One up-side for multihulls, and perhaps some power boats, is that our sinks are higher (we don't sit so deep in the water) and they drain straight away. Only the showers have sumps.

[rwidman]

Originally Posted by ranger42c

FWIW...

Both our sinks drain directly overboard, via outlets above the waterline.

Neither drain hose has a check valve, but both lines have P-traps -- which do tend to accumulate some spinach (carp?) from time to time, especially if we don't run enough fresh water through. (We understand P-traps are useful to keep odors, and/or perhaps genset fumes -- as from neighbors during a raft-up? -- out of the boat.)

The purpose of a water filled trap is to keep sewer gasses from coming up through the drain. Since the sink is not dumping into a tank, but directly overboard, no trap is needed. If you think odors or fumes from other boats may enter the boat through the drain, simply put the stopper in. Those odors or fumes will enter your boat if you open a door or window anyway.

[carstenb]

any smells fro mp-trap scan be eliminated by adding a bit of vinegar to the drain and leaving it overnight.

Dockhead, I'd try SWLs solution vinegar and then some bicarbonate of soda and let it slosh around for some days

[ranger58sb]

Originally Posted by rwidman

The purpose of a water filled trap is to keep sewer gasses from coming up through the drain. Since the sink is not dumping into a tank, but directly overboard, no trap is needed. If you think odors or fumes from other boats may enter the boat through the drain, simply put the stopper in. Those odors or fumes will enter your boat if you open a door or window anyway.

I tend to think of CO as being even more noxious than sewer gases

If we happen to be rafted with a gas boat's generator running, we usually don't open doors and windows, either.

I don't mind perhaps seeming to be over-cautious. OTOH, our traps are indeed way deeper than needed. I just reckon I'll improve that situation when it becomes necessary to do work on those discharge hoses for some other reason. In the meantime, I've no need to go looking for projects, when so many others loom...

Originally Posted by carstenb

any smells fro mp-trap scan be eliminated by adding a bit of vinegar to the drain and leaving it overnight.

Yep, sometimes we use that instead.

-Chris

[ontherocks83]

Dockhead,
Not sure if this will work but what about filling the tank with hotish water and letting it soak. Drain most of that out and then add vinegar and baking soda to the tank and letting it soak. People used to do that to clean clogged drains. Might be worth a try and it keeps things environmentally friendly.

[rwidman]

Originally Posted by ranger42c

I tend to think of CO as being even more noxious than sewer gases

If we happen to be rafted with a gas boat's generator running, we usually don't open doors and windows, either.

I don't mind perhaps seeming to be over-cautious. OTOH, our traps are indeed way deeper than needed. I just reckon I'll improve that situation when it becomes necessary to do work on those discharge hoses for some other reason. In the meantime, I've no need to go looking for projects, when so many others loom...


-Chris

If you really believe you need a trap, all you have to do is put a loop in the drain hose. You don't have to buy and fit an actual trap.

[ranger58sb]

Originally Posted by rwidman

If you really believe you need a trap, all you have to do is put a loop in the drain hose. You don't have to buy and fit an actual trap.

Yep, that's how the builder did it. Sorry I wasn't clear: it's a "virtual" trap, I guess.

-Chris

[prosneek]

Originally Posted by a64pilot

There are several chemicals specifically made for the grey water tanks, but dishwashing machine liquid works well too as it doesn't create suds. You can also toss a dishwashing machine tablet or two in the bilge every so often and it will keep it spotless. watch this link.

That's very handy to know and an easy solution. Thanks for sharing.