I want to add the ability to hose out my holding tank from the deck. I already have the deck fitting and hoses, but im not sure the best way to add a fitting to my plastic tank. The existing holes in the tank came with pre-tapped threads for the fittings. Is it easy to add new fittings? Where can i buy them?
Holding tank - adding new fittings
- Thread starter theredboat
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No real need to add another fitting...
'Cuz you can use the pumpout fitting to hose out the tank...and should, 'cuz putting water into the tank via the deck pumpout sends the water into the tank at the bottom to stir up any sludge and hold in suspension so it can be pumped out.
If you insist on adding another fitting, the only place it should go is on the top of the tank, with a pickup tube inside to the bottom...installing it at the bottom is just asking for a leak. And omitting the pickup tube won't let you remove the sludge very easily. It's not that hard to do, thanks to a li'l doodad called the Uniseal UNISEAL You'd be able to use a piece of PVC pipe as a fitting. You'll find quite a bit of info on doing this in the discussions in this forum.
'Cuz you can use the pumpout fitting to hose out the tank...and should, 'cuz putting water into the tank via the deck pumpout sends the water into the tank at the bottom to stir up any sludge and hold in suspension so it can be pumped out.
If you insist on adding another fitting, the only place it should go is on the top of the tank, with a pickup tube inside to the bottom...installing it at the bottom is just asking for a leak. And omitting the pickup tube won't let you remove the sludge very easily. It's not that hard to do, thanks to a li'l doodad called the Uniseal UNISEAL You'd be able to use a piece of PVC pipe as a fitting. You'll find quite a bit of info on doing this in the discussions in this forum.
Here's my thread on the subject started before a lot of testing that there is a link to in the thread.
http://forums.sbo.sailboatowners.com/showthread.php?t=126961
I've just had a lot of problems with a tank built by a fabricator who was still learning and have been filling it with air and soaping all the seams. I've been soaping the Uni-Seals at the same time and not seen a hint of leakage at 1 - 3 psi. I even wiggled them a bit. These things are great and tight. When I had to take my tank out to have the seam leaks fixed (before use fortunately) it was a 10 minute job to pull the fittings out instead of an hour. Much faster and easier install as well.
This test rig didn't blow up until about 10 psi.
The one thing I haven't seen documented about them is that, at least in cooler weather, soaking them in boiling water just taken off the stove for about three minutes is necessary to get the pipe in.
K-Y isn't something I keep around the house. I figured that I would be better off using the recommended Windex which pretty much disappears than something that would be more persistent. The heat and Windex combination worked great in 50 degree basement. I noticed while putting plugs in this tank for testing that heat may not be necessary at 70 degrees.
BTW I just about ruptured a disk getting one of the 1 1/2" fittings out. These things really hold. Wiggling back and forth and letting some soap solution drip down in it as I did so helped. I had to turn it with a pipe wrench to finally get it moving. I made the mistake of not making the blanked test plugs long enough to get a good grip. The other fittings had elbows on top and the extra leverage made them much easier to remove.
Trying very hard to stay on thread
redface, K-Y contains very little that will not dry, given time, as most of the lubrication comes from glycerine:Chemical CAS# or ID % Water
007732-18-5 54 Glycerin
000056-81-5 30 Sorbitol
000050-70-4 10 Propylene glycol
000057-55-6 5 Hydroxyethyl cellulose
009004-62-0 - Benzoic acid
000065-85-0 - Methylparaben
000099-76-3 - Sodium hydroxide
001310-73-2 -
In fact, glycerine is very useful for these sorts of things. I have also found a thin film of glycerine works well for sealing tiny leaks in inflatable valves. Very safe with the elastomers in question. It is a favorite lubricant around chemical plants, when fitting seals that are not petroleum tolerant.
Another clue as to whether a substance leaves a residue is whether the bottle becomes messy with dried residue, as some cleaner containers do. K-Y and glycerine do not.
Thanks for the very complete run down on something I don't have much familiarity with. I do keep glycerine on board for pre-lubricating water pump impellers so it's good to know it has other uses.
I think the issue with Uni-Seals in low temperatures is not so much a matter of lubrication as the clever shape. There is a beveled bottom to the socket that extends below the hole into the tank. When the pipe or fitting is pushed in, the bevel is pushed out which presses the sleeve against the sides of the hole and also makes the Uni-Seal neck larger than the hole. It is the stiffness of doing the material, both in bending and the required stretching, that is a problem at lower temperatures.
That's the whole point...Trying very hard to stay on thread
Dishwashing liquid has always been the recommended lubricant for fittings because it dries out. Grease and oil don't...hoses can work their way back off fittings. K-Y works even better because it's a LOT slipperier than dishsoap and also dries. but dries out.
You might not have to try so hard to stay on thread if you keep in mind that K-Y is actually a SURGICAL jelly that, like a lot of things, has a number of other good uses. It also has the added advantage of being both very inexpensive and readily available from any drugstore or grocery that has an OTC pharmacy area. I've touted its use in onboard plumbing for years...can't recall it ever causing anyone else have a problem staying on thread.
One of the things I do in my work is inspect very large oil tanks (licensed API inspector) and one of the tools of the trade is an ultra sound machine, simpler but not unlike those used in hospitals. There is a specific jell sold to go with the machine, but after the liquid and jell restrictions on air travel, it became a real hassle, sometimes even in checked bags. A chemical they could not identify. The solution in this case turned out to be hotel mini-conditioner bottles. You can take a bag of those through security and they just figure you're cheap, but harmless.
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