Peggy, Help me understand whether the following simple, cheap holding tank discharge plumbing idea would work: Short 1-1/2" hose from bottom fitting on tank to 1-1/2" hose T. From hose T to 1-1/2" waste pumpout on deck, sealed with O-ring. From hose T to 1-1/2" inlet of sewage-rated diaphram pump. From diaphram pump outlet to 1-1/2" thru-hull equipped with seacock for emptying holding tank off-shore. No Y-valves. (Head always flushes into upper 1-1/2" fitting on holding tank. Two 1" vent hoses from top of tank to near whale eye nav. lights in bow.) Seacock remains closed except while emptying tank offshore. Can I assume that the O-ring on deck fitting will seal well enough to prevent significant vacuume leak while using diaphram pump? Am I missing anything? Does this schematic sound like it would work? Thanks! -- Leon Sisson
- Status
Nothing inexpensive about head plumbing
Leon: There is not a cheap way to plumb the holding tank. You can buy cheap hose but then your boat will stink in about a year or two and you will end up spending the money and labor over again. The waste hose is about $8/ft. plus thru hulls, vent hose, vented loop, seacocks, pump, tank etc. Check out the West Marine site or their catalog. They have this all laid out for different types of configurations.
Leon: There is not a cheap way to plumb the holding tank. You can buy cheap hose but then your boat will stink in about a year or two and you will end up spending the money and labor over again. The waste hose is about $8/ft. plus thru hulls, vent hose, vented loop, seacocks, pump, tank etc. Check out the West Marine site or their catalog. They have this all laid out for different types of configurations.
exact same on '84 H31.
What you describe is how my H31 was plumbed when it came to me. I just replumbed it and put in a "y" valve so stuff was not sitting in the hose to the thru hull. Considering how much all the hose and pump costs, the "y" was a relatively cheap addition ($40).
What you describe is how my H31 was plumbed when it came to me. I just replumbed it and put in a "y" valve so stuff was not sitting in the hose to the thru hull. Considering how much all the hose and pump costs, the "y" was a relatively cheap addition ($40).
I think you just reinvented the wheel 
You've just described almost perfectly one of the schematics in the WM catalog. As for preventing a vacuum leak while using the macerator to pump out...that's the last thing you want to do. Whether pumping out or pumping overboard...whether you're pumping sewage or pumping water of fuel, pulling a vacuum will prevent the tank from emptying....and while I doubt your macerator has enough suction to do it, a really strong pumpout could implode your tank. That's one of the reason all tanks--water, fuel and sewage holding alike--are vented, and why a blocked vent line or thru-hull spells big trouble. So I wouldn't both with the o-ring unless the fitting is designed to use one.
You've just described almost perfectly one of the schematics in the WM catalog. As for preventing a vacuum leak while using the macerator to pump out...that's the last thing you want to do. Whether pumping out or pumping overboard...whether you're pumping sewage or pumping water of fuel, pulling a vacuum will prevent the tank from emptying....and while I doubt your macerator has enough suction to do it, a really strong pumpout could implode your tank. That's one of the reason all tanks--water, fuel and sewage holding alike--are vented, and why a blocked vent line or thru-hull spells big trouble. So I wouldn't both with the o-ring unless the fitting is designed to use one.
Let Me Try To Clarify
OK, let's forget I used the word "cheap" in reference to anything having to do with boats. Yes, I studied the West Marine MSD diagrams before coming up with this scheme. My reinvented wheel comes closest to their "Our Favorite Method", but their's seems to use a Y-valve, for which I'm suggesting substituting a hose T. I agree this doesn't save a significant percentage of the system parts cost, but it seems like it would simplify the installation and operating procedure a bit (no need to provide for Y-valve rigid mounting and handle access). As for vacuume damage to the tank, with two 1" vent lines this seems unlikely. I'm not planning to use a macerator, just a manual diaphram pump, similar to a manual bilge pump, but rated for sewage handling (care to reccommend one?). The O-ring vs. vacuume leak I was referring to is the possibility of the deck pumpout fitting leaking air into the discharge line while in offshore dump mode, allowing the manual pump to suck air from the deck fitting through the hose T, rather than sewage from the holding tank. As for hose lengths/cost, my reinvented wheel system would use the same number and length of 1-1/2" discharge hoses as West's "Our Favorite Method", just no Y-valve. (The dual tank vents would add to the installation cost, but it's my understanding that good venting is critical to odor control.) Sorry if my original post was less than clear on these points. -- Leon Sisson
OK, let's forget I used the word "cheap" in reference to anything having to do with boats. Yes, I studied the West Marine MSD diagrams before coming up with this scheme. My reinvented wheel comes closest to their "Our Favorite Method", but their's seems to use a Y-valve, for which I'm suggesting substituting a hose T. I agree this doesn't save a significant percentage of the system parts cost, but it seems like it would simplify the installation and operating procedure a bit (no need to provide for Y-valve rigid mounting and handle access). As for vacuume damage to the tank, with two 1" vent lines this seems unlikely. I'm not planning to use a macerator, just a manual diaphram pump, similar to a manual bilge pump, but rated for sewage handling (care to reccommend one?). The O-ring vs. vacuume leak I was referring to is the possibility of the deck pumpout fitting leaking air into the discharge line while in offshore dump mode, allowing the manual pump to suck air from the deck fitting through the hose T, rather than sewage from the holding tank. As for hose lengths/cost, my reinvented wheel system would use the same number and length of 1-1/2" discharge hoses as West's "Our Favorite Method", just no Y-valve. (The dual tank vents would add to the installation cost, but it's my understanding that good venting is critical to odor control.) Sorry if my original post was less than clear on these points. -- Leon Sisson
I'd use a y-valve...
What would you save by using a tee or a wye instead...$30? OTOH, for a sailor, that's at least a year's supply of fuel! <lol> Seriously, the biggest problem with y-valves happens when they end up in the same position for months on end...that's what causes 'em to bind and what results in broken handles. (Same is true for seacocks, btw...which is anothe good reason to keep 'em closed except when you're actually using whatever they're connected to). But if you know you're gonna "excercise" yours a lot...you'll have less problems with dumping at sea, and the y-valve should last for years. Btw...be sure that your macerator is at or below the level of the discharge fitting on the tank. If it's not, it has to run for several seconds before it primes...and the friction heat from running dry is what "fries" impellers. And ALWAYS carry a spare aboard...they have a nasty habit of failing anyway. One more thing about impellers--and this applies to ALL impellers, not just the ones in macerators: sitting unused for a long time--like over the winter--dries out neoprene, which is what impellers are made of. Tthey can also get stuck...starting 'em up again puts tremendous stress on an already weakened impeller. So it's a good idea to replace and lubricate all of 'em every spring...and ALWAYS carry a spare for every impeller on the boat...'cuz even brand new impellers can fail, given the right circumstances...if you have one, it's a simple fix...if you don't, it can mean anything from a holding tank you can't empty to an engine you can't run when you need it most.
What would you save by using a tee or a wye instead...$30? OTOH, for a sailor, that's at least a year's supply of fuel! <lol> Seriously, the biggest problem with y-valves happens when they end up in the same position for months on end...that's what causes 'em to bind and what results in broken handles. (Same is true for seacocks, btw...which is anothe good reason to keep 'em closed except when you're actually using whatever they're connected to). But if you know you're gonna "excercise" yours a lot...you'll have less problems with dumping at sea, and the y-valve should last for years. Btw...be sure that your macerator is at or below the level of the discharge fitting on the tank. If it's not, it has to run for several seconds before it primes...and the friction heat from running dry is what "fries" impellers. And ALWAYS carry a spare aboard...they have a nasty habit of failing anyway. One more thing about impellers--and this applies to ALL impellers, not just the ones in macerators: sitting unused for a long time--like over the winter--dries out neoprene, which is what impellers are made of. Tthey can also get stuck...starting 'em up again puts tremendous stress on an already weakened impeller. So it's a good idea to replace and lubricate all of 'em every spring...and ALWAYS carry a spare for every impeller on the boat...'cuz even brand new impellers can fail, given the right circumstances...if you have one, it's a simple fix...if you don't, it can mean anything from a holding tank you can't empty to an engine you can't run when you need it most.
- Status