Hi Peggy, Well, I'm getting ready to install my holding tank system--finally--after about 6 months worth of research and motivational seminars! ;-) I've read through your (excellent) book about three times; it's now dog-eared and worn out and I've followed its advice as closely as possible while designing my system. I have a Catalina 30 and after much contemplation over other possible customized locations, I've decided my only real choice is to put the tank where the factory puts it--under the port settee. Understanding after reading your book the importance of proper venting, I tried to figure out a way to run a vent line at a 45-degree angle somewhere, but it's just impossible based on the design of the boat. So, I'm having to do what the factory does, vent-wise: run the line up almost vertically behind the settee. :-( However, where the factory vents to the bottom of a stanchion on the deck, I'm using a larger 1" hose and am running it out the topside. Also, since I am forced into this highly ineffective venting design, I've decided to put in a second vent line--also 1"--emptying out either the transom or the aft port topsides. I'm hoping this will at least provide a little air flow. So, in tweaking the final parts of my design, I've come across two items about which I'd like your opinion (with the understanding that I have NO holding tank experience at all): The first is the idea that I think it would be sensible to put a shutoff valve on the pumpout line, as close as possible to the tank fitting. Considering that the pumpout fitting is at the bottom of the tank, and that my pumpout line runs upward to the stern at a relatively shallow angle, it seems like the contents of the tank would be continually sloshing down the hose 5-10'. Yet, as logical as this sounds to me, I haven't seen a shutoff valve mentioned in the 3-4 books that describe marine plumbing systems in detail, nor do there seem to be any 1 1/2" "shutoff valves" sold anywhere that I can find. So, I'm worried that I'm missing something here. The second item is related. It is a "check valve" that is sold ostensibly for holding tanks and which "reduces back pressure" to facilitate easier pumpout. I'm assuming that this is just a one-way valve installed downstream of the pumpout fitting. At first, I thought this might serve my purpose, but then realized that in order to pump-out the tank, the valve would have to allow stuff out, but nothing in--opposite of what I need. However, there is not much of a description of this product, so I'm not real sure that's what it does. Also, can I assume that after a pump-out that I'm going to want to shoot some water back into the tank via the pumpout fitting and suck it out again to get the tank as clean as possible? If this is true, than this "check valve" wouldn' seem to allow me to do this. Hoping you can reduce my confusion..... Barry
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Maybe to shutoff valve, no to check valve
If you plan to install a macerator to dump the tank at sea, a shutoff valve--which can be a y-valve instead of just a tee--in the tank discharge line as close to the tank as possible is a good idea...so you can close off the flow to the macerator to service it. Otherwise, you don't really need it. The check valve is not a good idea. I can't even imagine what useful purpose it would serve. SeaLand offers a "pressure relief" valve that's supposed to save you from a blocked vent during pumpout...but it can fail too. Btw...do you have enough clearance above the top of the tank--at least 5"--to move the pumpout fitting to the top? That would eliminate any standing waste in the pumpout line. Where'd you get the tank?
If you plan to install a macerator to dump the tank at sea, a shutoff valve--which can be a y-valve instead of just a tee--in the tank discharge line as close to the tank as possible is a good idea...so you can close off the flow to the macerator to service it. Otherwise, you don't really need it. The check valve is not a good idea. I can't even imagine what useful purpose it would serve. SeaLand offers a "pressure relief" valve that's supposed to save you from a blocked vent during pumpout...but it can fail too. Btw...do you have enough clearance above the top of the tank--at least 5"--to move the pumpout fitting to the top? That would eliminate any standing waste in the pumpout line. Where'd you get the tank?
No Macerator & Ronco B-123
Peggy, The tank is a B-123 from Ronco. They made the fittings to order. I'm surprised at your statement to have the pumpout fitting at the top of the tank. How would the vacuum empty the tank if there are open vent line? Wouldn't it just suck air?????? BTW, I'm sending the tank back to Ronco today to have two the vent fittings modified. Right now, the vent fittings are too high and the tank won't fit. So, if necessary, I could also have them modify the pumpout fitting... I'm not having a macerator in the system. I'm also installing a Lavac toilet and will be using it's pump to empty my tank when offshore. Are you saying that the shutoff valve isn't necessary because having the sludge sloshing around in the hose all the time won't cause odor? Thanks, Barry
Peggy, The tank is a B-123 from Ronco. They made the fittings to order. I'm surprised at your statement to have the pumpout fitting at the top of the tank. How would the vacuum empty the tank if there are open vent line? Wouldn't it just suck air?????? BTW, I'm sending the tank back to Ronco today to have two the vent fittings modified. Right now, the vent fittings are too high and the tank won't fit. So, if necessary, I could also have them modify the pumpout fitting... I'm not having a macerator in the system. I'm also installing a Lavac toilet and will be using it's pump to empty my tank when offshore. Are you saying that the shutoff valve isn't necessary because having the sludge sloshing around in the hose all the time won't cause odor? Thanks, Barry
When the discharge is on the top of the tank
There's a pickup tube inside the tank that goes to the bottom (you must have missed that in my book). But if you don't have enough room above the top of the tank for vent fittings that only protrude 1/2" above the tank, you definitely don't have room to put the discharge on the top of the tank. Keeping waste out of the discharge line won't prevent that line from permeating unless you ALWAYS rinse out the tank and the discharge line VERY thoroughly immediately after pumping out or dumping the tank....'cuz the residue of waste will still produce the gasses that permeate hoses. One solution might be to use hard PVC for the tank discharge. But you'd still need to use enough hose at each end to absorb shock...and unless that line is pretty straight, you'd have too many unions (potential leakers) in it for it to be a GOOD solution. So a shutoff valve won't prevent permeated hose, and unless you plan to put the Lavac pump in a very strange location, there's nothing to be gained with a shutoff valve.
There's a pickup tube inside the tank that goes to the bottom (you must have missed that in my book). But if you don't have enough room above the top of the tank for vent fittings that only protrude 1/2" above the tank, you definitely don't have room to put the discharge on the top of the tank. Keeping waste out of the discharge line won't prevent that line from permeating unless you ALWAYS rinse out the tank and the discharge line VERY thoroughly immediately after pumping out or dumping the tank....'cuz the residue of waste will still produce the gasses that permeate hoses. One solution might be to use hard PVC for the tank discharge. But you'd still need to use enough hose at each end to absorb shock...and unless that line is pretty straight, you'd have too many unions (potential leakers) in it for it to be a GOOD solution. So a shutoff valve won't prevent permeated hose, and unless you plan to put the Lavac pump in a very strange location, there's nothing to be gained with a shutoff valve.
Aha!
Peggy, Thanks for the clarification about the shut-off valve and the pump-out fitting being on the top of the tank. It makes sense, now. While I plan to thoroughly flush the tank religiously after emptying it at my slip (my marina has a portable sucker-outer), I'm sure that won't be possible in all locations or situations. And, since I'm only planning to own the boat for 2-3 more years, if I buy good sanitation hose, I probably won't experience any permeation odors myself. Right? Barry
Peggy, Thanks for the clarification about the shut-off valve and the pump-out fitting being on the top of the tank. It makes sense, now. While I plan to thoroughly flush the tank religiously after emptying it at my slip (my marina has a portable sucker-outer), I'm sure that won't be possible in all locations or situations. And, since I'm only planning to own the boat for 2-3 more years, if I buy good sanitation hose, I probably won't experience any permeation odors myself. Right? Barry
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