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Boat Forum / Building / February 2007Head sink to grey water tank pipe angle
Does anyone know what the mimimum slope of this drain can be that will not cause clogging? I really do not want to use a second grey water tank in the forward end which will cause loss of space and another through hull fitting. It is preferable to use one large tank for the whole boat. Steve > Does anyone know what the mimimum slope of this drain can be that will not > cause clogging? I really do not want to use a second grey water tank in the > forward end which will cause loss of space and another through hull fitting. > It is preferable to use one large tank for the whole boat. > Steve In land based applications it's 1/4" per 12" of run. Boats are entirely different because they can have a permanent heel or trim. So I'd allow 1" per 12" on a small boat. Evan Gatehouse Evan, Thanks for the info. I also think 1/4" is too shallow, but I did not know the recommended gradient. I will have to measure, but I think I can make 1" per foot of run work. Steve >> Does anyone know what the mimimum slope of this drain can be that will >> not cause clogging? I really do not want to use a second grey water tank [quoted text clipped - 8 lines] > > Evan Gatehouse > Does anyone know what the mimimum slope of this drain can be that will not > cause clogging? I really do not want to use a second grey water tank in the > forward end which will cause loss of space and another through hull fitting. > It is preferable to use one large tank for the whole boat. Why are you installing a gray water tank? Gray water (galley, bath and shower water) can go directly overboard in all coastal waters and, except for only 2 or 3 places, on all inland waterways too. If you're mistakenly referring to toilet waste (black water) as gray water, holding tanks should be within about 6' of the toilet--'cuz that's as far as bowl contents will move in the amount of time anyone will spend flushing. So if you want to avoid leaving waste sitting the line, a single large tank to serve two toilets at opposite ends of a larger boat isn't a good solution. If you're thinking of combining black water and gray water in the same tank, CG regulations won't allow it. Gray water and black water plumbing and tanks must be completely separate...can't even share a common vent.  SignaturePeggie ---------- Peggie Hall Specializing in marine sanitation since 1987 Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and Other Sources of Aggravation and Odor" http://shop.sailboatowners.com/books/detail-books.htm?fno=0&sku=90&cat=1304 Peggie, Thank you for your reply. No, I have no intention of combining black and grey water. The application is a sailboat. Sailboats live on their ear. All drains are effectively below the waterline. In that light, draining through conventional water traps into a large grey water tank with one through hull and a single pump and check valve allow facility useage under all points of sail in all weather conditions. To me, this is highly desireable and is a better solution than shutting all outboard drains in heavy weather. This solution is not available to all designs. There must be adequate headroom and bilge depth to facilitate it. Steve >> Does anyone know what the mimimum slope of this drain can be that will >> not cause clogging? I really do not want to use a second grey water tank [quoted text clipped - 15 lines] > tank, CG regulations won't allow it. Gray water and black water plumbing > and tanks must be completely separate...can't even share a common vent. Have you considered installing sumps instead of a tank? Gray water tanks, because they contain food particles, cooking grease, soap scum body oils and a whole bunch of other thing are MUCH harder to maintain and keep odor-free than black water tanks. Sumps, otoh, can easily be flushed and cleaned...they'd solve your problem and be so much easier to maintain than a tank. Otoh, maybe what you're thinking IS a sump...how large a gray water tank are you envisioning? Peggie > Peggie, > Thank you for your reply. No, I have no intention of combining black and [quoted text clipped - 26 lines] >> tank, CG regulations won't allow it. Gray water and black water plumbing >> and tanks must be completely separate...can't even share a common vent. SignaturePeggie ---------- Peggie Hall Specializing in marine sanitation since 1987 Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and Other Sources of Aggravation and Odor" http://shop.sailboatowners.com/books/detail-books.htm?fno=0&sku=90&cat=1304 Peggie, Yes, your description is better than mine, it is a sump. The sump(tank) will be about 10 to 15 gallons with a float switch for the pump. Steve > Have you considered installing sumps instead of a tank? Gray water tanks, > because they contain food particles, cooking grease, soap scum body oils [quoted text clipped - 39 lines] >>> tank, CG regulations won't allow it. Gray water and black water plumbing >>> and tanks must be completely separate...can't even share a common vent. > The sump(tank) will > be about 10 to 15 gallons with a float switch for the pump. When you were describing it as "large gray water tank" I had visions of something 30+ gallons. :) 10 is easily manageable...15 can be managed, but not as easily. Since it'll be pumped overboard automatically, you may even find that 5-6 is large enough unless you have a cast of thousands aboard, all running water at the same time. There's an easy way to keep both the tank and the float switch clean and sweet smelling without ever having to manually clean either one: Raritan C.P. is a bio-enzymatic cleaner that not only destroys odor on contact, but the enzymes in it "eat" hair, soap scum, grease and all the other stuff that turns a sump into a smelly primordial soup. Fill the sump at least half full with clean water and put about 4 oz down a drain--or an ounce or two down each one of the drains--when it can stand at least overnight...then flush the sump out with plenty of clean fresh water. It's the only job on boat that I know of that requires -0- manual labor. Peggie > Steve > [quoted text clipped - 41 lines] >>>> tank, CG regulations won't allow it. Gray water and black water plumbing >>>> and tanks must be completely separate...can't even share a common vent. SignaturePeggie ---------- Peggie Hall Specializing in marine sanitation since 1987 Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and Other Sources of Aggravation and Odor" http://shop.sailboatowners.com/books/detail-books.htm?fno=0&sku=90&cat=1304 Thanks Peggie. Your expert help is very welcome. Steve >> The sump(tank) will be about 10 to 15 gallons with a float switch for the >> pump. [quoted text clipped - 65 lines] >>>>> plumbing and tanks must be completely separate...can't even share a >>>>> common vent. > Peggie, > Thank you for your reply. No, I have no intention of combining black and [quoted text clipped - 7 lines] > and bilge depth to facilitate it. > Steve I don't know Steve, it does depend on the boat and the location of the sink. Our galley sink (well outboard under the side deck) on our 30' monohull would fill slightly if the boat spent hours on one tack in rough weather (heeling more than normal). Never enough to get on the counter though. The head sink was closer to centerline and never saw a drop from heeling. Sinks closer to centerline are much better in this regard. Oh if you do fit a sump tank, make sure you have a means to clean it out often. Our shower sump tank got really funky when we showered regularly. Evan Gatehouse |
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