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Old 19-03-2010, 07:14   #16
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The gentleman who posted the query is from the north shore of Massachusetts. He either sails in the Atlantic Ocean or the Atlantic Ocean. There is no requirement for the Y valve to be locked anywhere I have been except in Florida. He, therefore, will be doing the majority of his sailing in open waters and has no need to foul the interior of the boat with the odor that is generated from the holding tank and the associated hoses. This odor problem has been an ongoing discussion on this forum, and others. If a problem can be eliminated, do so, especially where it is both beneficial (to the boat occupants) and not harmful to the environment or other.
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Old 19-03-2010, 07:56   #17
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The gentleman who posted the query is from the north shore of Massachusetts. He either sails in the Atlantic Ocean or the Atlantic Ocean. There is no requirement for the Y valve to be locked anywhere I have been except in Florida. He, therefore, will be doing the majority of his sailing in open waters and has no need to foul the interior of the boat with the odor that is generated from the holding tank and the associated hoses. This odor problem has been an ongoing discussion on this forum, and others. If a problem can be eliminated, do so, especially where it is both beneficial (to the boat occupants) and not harmful to the environment or other.
Don't folks anchor in Massachusetts? I hope he can hold it if he does.

Jim
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Old 19-03-2010, 07:58   #18
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He either sails in the Atlantic Ocean or the Atlantic Ocean. There is no requirement for the Y valve to be locked anywhere I have been except in Florida.

If you check the USCG web site, they are now requiring that Y-valves be secured anytime you're inside of the three mile limit. At one time it was only Florida, but not any more.
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Old 19-03-2010, 10:48   #19
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I'll second Carl's recommendation for the most part. If you don't want another below the waterline through-hull, then plumb the holding tank the the existing below the waterline through-hull. Instead of a shower sump, though I'd just add an above the water line through-hull for the sink. Just above as people have said.

I have a system that is simple and efficient on one of my boats that I really like. It's used on many of the Moorings charter boats:

Head pumps to top of holding tank. No vented loop is needed since the tank is vented and always has air at the top which prevents back siphoning.

The bottom of the holding tank is just above the water line with an almost straight vertical run from the bottom of the tank to a seacock. Simply open the seacock to drain the tank. You can also just leave it open when legal and appropriate for direct discharge. Since the out take is at the very bottom of the tank, it's easy to flush the tank well simply by pumping a bit more raw water through the head.

This system has no inside vented loop to smell, requires no second waste pump, allows one to hold waste or not as appropriate, has no elbows or horizontal discharge hose for waste to collect or clog, is the most odor free system I've ever seen and meets coast guard regs. I don't know why it isn't standard.
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Old 19-03-2010, 11:45   #20
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I'll second Carl's recommendation for the most part. If you don't want another below the waterline through-hull, then plumb the holding tank the the existing below the waterline through-hull. Instead of a shower sump, though I'd just add an above the water line through-hull for the sink. Just above as people have said.

I have a system that is simple and efficient on one of my boats that I really like. It's used on many of the Moorings charter boats:

Head pumps to top of holding tank. No vented loop is needed since the tank is vented and always has air at the top which prevents back siphoning.

The bottom of the holding tank is just above the water line with an almost straight vertical run from the bottom of the tank to a seacock. Simply open the seacock to drain the tank. You can also just leave it open when legal and appropriate for direct discharge. Since the out take is at the very bottom of the tank, it's easy to flush the tank well simply by pumping a bit more raw water through the head.

This system has no inside vented loop to smell, requires no second waste pump, allows one to hold waste or not as appropriate, has no elbows or horizontal discharge hose for waste to collect or clog, is the most odor free system I've ever seen and meets coast guard regs. I don't know why it isn't standard.
I have been giving this specific conversion serious consideration for a while - any negatives?
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Old 19-03-2010, 12:16   #21
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one negative already pointed out is that if you have a plastic tank you probably don't want a fitting on the bottom since they do tend to fail at the worst time.
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Old 19-03-2010, 12:28   #22
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The only negative I see is the recommendation for a drain vertcally out of the bottom into the through hull. I had this arrangement on my boat with the exception of the fact I had a macerator pump on the drain to actively pump the waste overboard. I spent about a year without going off shore and draining the vertical pipe. Note that this pipe is not evacuated when using a pump out. Solid organic material at the bottom of the tank including stuff like biodegradeable toilet paper fibers will tend to settle inthe pipe. If the pipe is not evacuated regularly this debris accumulates and turns into something resembling concrete. When you open the seacock, nothing happens then you have to figure uout how to get the stuff out of the tank. This happened to me twice before I redesigned the system. I had a spare macerator and rigged it with duct tape to pump the waste over the side. The only way to get the thing unclogged was to remove the hose. Understand that the pump out leaves a couple of callons of waste in the bottom of my 60 gallon tank. When we pulled the hose off that waste dumped into the bilge. You might actually guess where one might be positioned when removing that hose as well. It took nearly an hour with a coat hanger to break up the clog and clean the hose. We then flushed a few hundred gallons of seawater through the bilge with our washdown pumps and pumped it overboard. We then washed all the surfaces with clorox and rinsed it again. Most of these Mooring boats referred to are offshore every week and this is probably never a problem because the hose is flushed regularly. If you are never going to be in inshore waters for an extended period this is probably not a problem for you, but if you are, this design could result in a very unpleasent experience. I reengineered my system so the overboard drain goes vertically upwards to a couple of inches above the tank and then loops back down to the pump then overboard. It takes a few seconds for the pump to prime the line but it doesn't clog and we'll never have a repeat of our previous experience.
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Old 19-03-2010, 12:41   #23
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If the sink is high enough to gravity drain to the bootstripe, that's much better than the showersump. But I think the Cabot 36 sink drain is too low - and it is also a deep sink and off-center. On starboard tack you certainly don't want your sink to sink you

A gravity drain holding tank is also great - but again, the bottom of the tank has to be high enough to drain. This usually means putting the tank right up under the side decks. Most boats have other uses for that space.

If you do have to use a pump, I would lead the hose from the top of the tank. A hose that exits at the bottom of the tank always has pressurized sewage in it and will start stinking sooner. By the way, I've had great luck with Trident 101 (102 in white) hose. Relatively flexible and no stink (yet).

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Old 19-03-2010, 13:29   #24
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I have been giving this specific conversion serious consideration for a while - any negatives?
Every sewage system has its negatives. There's nothing positive in my mind about having sewage on a boat. However, I've been far happier with this than any other system I've had. Another boat I've had sucked the sewage out from the top. The big problem with that was that there was always about 4 inches of sewage left on the bottom and that it would fail if the suction was anything less than perfect. I prefer to work with gravity than fight it.

Any hose can clog, any through-hull can freeze and drain fitting can leak. However, I feel a short straight gravity system offers less chance of this than other systems with fewer parts to fail. Replacing the short section of hose (after pumping lots of non-sewage water through) would be easy and cheap preventative maintenance.

I personally don't see how sewage buildup would occur any faster with this system than one that pumps the tank out instead. Actually, I think the movement of seawater and ease of pumping lots of fresh in helps keep things cleaned out. (Since it just flows out it's little effort to toss all sorts of water in. I tell guests to pump a whole lot of raw water through the system) I also see putting the drain at the bottom of the tank as a plus as it will drain the tank more completely. No matter where you put the discharge fitting, you will have sewage to that level. I'd prefer that level be at the absolute bottom. While unpleasant, any failure here is far less dangerous than a through -hull failure and I think unlikely if the fitting is properly installed.

One can get sewage build up at the bottom of the tank but this is true regardless of whether the discharge hose is connected to a pump or gravity feed. However with gravity feed, there is no sewage pump to fail or clog. Ideally, I'd like to install an inspection port on the top of the tank directly above discharge, so the discharge could be snaked out from above (As well a pressurized water to clean) Mine has never blocked, but if it did, it's a short straight cleaning job from below with anything straight that fits. Maybe not the most pleasant, but I prefer that to taking a clogged hose off a full tank inside the boat...

I know all the Moorings boats use larger than typical discharge hose and through hulls, but several forum members have indicated they use standard size with this same set up. Consider that the downside of an anti-siphon discharge exits mostly by gravity as well. The pump pumps sewage to the top of the loop, but due to the anti-siphon, it's mostly gravity after that. There is no (or at least little) pressure due to the anti-siphon hole. The system I described uses a shorter, straighter run which is at least partially cleaned by sea water.

To address a previous post: The system on this boat is used almost exlusively where it can be emptied at sea often. However, one doesn't need to add y-valve or install a second outtake for pump out. A simple t-fitting above the through hull will do the trick and preserve the straight inline discharge to the sea while using the same holding tank discharge fitting thus keeping it free. Since it's gravity release not pressure, having a hose snake far up to a deck fitting won't compromise the system at all. Simply close the through hull for dockside pump out and you are emptying the tank to the very bottom. Alternatively you could use a second discharge fitting at the bottom of the tank for the pump out so you have a complete backup system for emptying, but the trade-off would be the issue Captain Bill mentioned.

For context, other systems I've had on cruising boats have included: RV type head (The other boat I own now) with integrated holding tank that can be pumped out, composting head, holding tanks that get sucked out from above with hand pump and holding tanks that get pumped out via lower fitting. For me the gravity feed system has proved to be the simplest and most odor free of all of them.

I think the big challenge with a pre-exisitng head is weather or not it's feasible to place the holding tank just above the water line so that it flows easily and hopefully straight down to a through hull. Often existing through hulls, cabinetry, liners, etc make this a logistical challenge. On many of the Moorings boats, the tank is just behind the bulkhead and the through-hull is conveniently located under the bathroom sink. (Meaning it's not quite a straight discharge, but close.) Some have the through-hull in the cockpit lazarette which is a really an inaccessible location.

I'll add: Every boat, cruising location and use is different. While I really like this system in general, I'm not arguing it's the best choice for every boat or boat owner.
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Old 19-03-2010, 13:50   #25
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Smelly Stuff

I cannot tell if you have been using a porta potty type head up to this point, but I surmise that is the case. You have up to this point removed the waste completely from the boat. I know it's a pain, I did the same thing for 20 years and suffered anytime I neglected to follow through and dump the porta potty. My new (to me) boat had (emphasis, had) a stainless holding tank set up as you have detailed, however there are two seperate through hulls for grey water and black water. The stink was horrific, the system turned the whole boat into a sewage barge. Not good.

Beware of any system that even remotely vents any vapor to any sink or vented loop that cannot be positively evacuated overboard. One of the worst offenders on my boat was hose. If you use it you will need to replace it frequently. It may not be easy to get at and remember what has been in there as your yanking it out. I already had the required through hulls so I installed a very complex and odor tight pvc system that is suction evacuated by large whale pump. The tank has a positive pressure flush to aid pumpout and reduce deposits. Grey water is totally separate and has it's own pump and a small maniforld equiped with a whale pump float switch and a check valve to prevent back flow of grey water into the manifold. This system requires the boat to be kept properly heated during winter.

Bottom line, build a tight system with correct anti siphon provisions. Don't plan to store black or grey water on the boat for any length of time. Sinks stink and tanks plug. I almost wish I had stayed with a more delux porta potty.

Todd
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Old 13-04-2010, 19:54   #26
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Jentines' reply is spot on.

Howie mandel (a noted germophobe) would have a stroke!!!!!

The smell for one....the remnants creeping up the hoses.

I really don't understand why people are such hole-a-phobes,,,,
I second Jentine and third Cheng!!! Keep sanitary seperate from everything else. Boats are boats, and if it can go wrong, it will, and at the worst possible time and manner.
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Old 10-12-2013, 20:08   #27
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Re: Holding Tank Configuration Question

As the person who made the original post, I'm following up to say this installation is working flawlessly after three years. I've never had a single issue with odor or blockage. My discharge hose exits on the side of the tank, near the top, and draws from a dip stick. I ran 3/4-inch vent hoses through the front and rear of the tank, exiting them on deck. The folks at Ocean Link (RI), where I bought my tank, provided some very helpful advice regarding design and installation. The Whale discharge pump is easy to operate and trouble-free. It was a bigger project than I bargained on due to the challenges of getting a 30-gallon tank under a berth, but I'm glad I did it.
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