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Go Back   SailNet Community > On Board > Gear & Maintenance > That Darn PO!!
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Thread: That Darn PO!! Reply to Thread
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Topic Review (Newest First)
10-21-2012 07:31 AM
dacap06
Re: That Darn PO!!

Bingo! The light has finally come on.

Thanks, Gary!

Tom
10-20-2012 11:31 PM
GaryHLucas
Re: That Darn PO!!

Tom,
An angle drill like a milwaukee will probably fit with no problem.

If you read what I wrote earlier, about using a tape measure to reach across the tank you'll see you don't need to reach inside. You can use the tape measure to pull in a thin rope. slip the bulkhead over the rope and tie a large nut or ring (1/2" long piece of pvc pipe) on the rope so you can pull the bulkhead into the tank. Leave a tail on the rope, if you forgot the gasket you are going to need to pull it back out! Once the bulkhead is pulled through the hole you can grab it from the outside and put the nut on. The nut usually has left hand threads, and the gasket inside the tank grips well enough that it won't turn as you tighten the nut. Occasionally you have to hold the outside end with pliers, but most of the time not.

On one job we used the wrong gasket material, I had to pull out and replace 27 bulkhead fittings, so I know this technique works.

Gary H. Lucas
10-20-2012 10:26 PM
dacap06
Re: That Darn PO!!

Quote:
Originally Posted by GaryHLucas View Post
Tom,
A Banjo brand 1/2" or 3/4" bulkhead fitting in Polypropylene is less than $7. It fits through a tank port of 2-3/4" and requires a 1-5/8" hole in the tank. So if you can enlarge the existing hole to 1-5/8" you are in pretty good shape. You don't need for your arm to fit in there.

I don't think spin welding with the tank in place can be done, and I doubt they can weld a new fitting where the old one is. As I understand it the machine that spins the fitting is like a router, it spins the fitting very fast. I am actually looking into buying a spin welding machine because we use lots of plastic tanks and it could potentially save us a bundle with all the fittings we currently install.

Gary H. Lucas
The bulkhead that abuts the end of the tank is part of the "nav table table" which is less than a foot wide. I pull out a floor plate, which leads to the water pump in the middle of the well and a hole through which the nipple I screwed into the fitting passes through. I'll have to measure to see if there's room to get a drill in there. If so, making a 1 and 5/8" hole could be easy. It might be enough even to just drill out the entire current fitting, in which case all I need is a hole saw.

I don't understand your comment about not needing to put my arm in the tank. The tank is pretty big, its shape fits nicely within my settee ,and it accounts for hull curvature. The tank in question is Ronco Plastics tank model B145 - the model number is moulded right into the top. This 26 gal tank is 42"' long, 19" wide, an almost 12" tall. How can I position the mushroom on the inside of the bulkhead 21" away horizontally and 11" vertically from the current inspection plate and hold it there to screw the nut in on the outside of the bulkhead without putting my arm in the tank. I guess I'd better go find one of those banjo fittings. There's clearly something simple I'm missing here.

Tom
10-20-2012 09:34 PM
GaryHLucas
Re: That Darn PO!!

Quote:
Originally Posted by dacap06 View Post
Hellosailor,

Your latest post made me think about this problem some more. I reread what you and GaryLucas had to say about bulkhead fittings, and my understanding is a little better now. My current inspection port is only 4" across and I can't get my arm in far enough to reach the end of the tank. I've been meaning to install a 6" fitting anyway so I can get my biceps through it and clean out the precipates. Once I widen the hole so I can reach the end of the tank, a bulkhead fitting becomes practical.

Getting a hacksaw blade down the 1/2" gap to cut the outside end of the old fitting down flush with the wall could be interesting, but otherwise this is worth investigating. It meets all my criteria of bein repairable, replacable, free of chemicals, fairly permanent, and doesn't preclude replacing the tank if it comes to that.

Thanks for being persistent!

Tom
Tom,
A Banjo brand 1/2" or 3/4" bulkhead fitting in Polypropylene is less than $7. It fits through a tank port of 2-3/4" and requires a 1-5/8" hole in the tank. So if you can enlarge the existing hole to 1-5/8" you are in pretty good shape. You don't need for your arm to fit in there.

I don't think spin welding with the tank in place can be done, and I doubt they can weld a new fitting where the old one is. As I understand it the machine that spins the fitting is like a router, it spins the fitting very fast. I am actually looking into buying a spin welding machine because we use lots of plastic tanks and it could potentially save us a bundle with all the fittings we currently install.

Gary H. Lucas
10-20-2012 09:15 PM
dacap06
Re: That Darn PO!!

Hellosailor,

Your latest post made me think about this problem some more. I reread what you and GaryLucas had to say about bulkhead fittings, and my understanding is a little better now. My current inspection port is only 4" across and I can't get my arm in far enough to reach the end of the tank. I've been meaning to install a 6" fitting anyway so I can get my biceps through it and clean out the precipates. Once I widen the hole so I can reach the end of the tank, a bulkhead fitting becomes practical.

Getting a hacksaw blade down the 1/2" gap to cut the outside end of the old fitting down flush with the wall could be interesting, but otherwise this is worth investigating. It meets all my criteria of bein repairable, replacable, free of chemicals, fairly permanent, and doesn't preclude replacing the tank if it comes to that.

Thanks for being persistent!

Tom
10-20-2012 06:50 PM
SJ34
Re: That Darn PO!!

My vote would be for the suggestion to tap the outlet for the next size up NPT fitting. If the current size is 1/2 then go to 5/8, if 5/8 then up to 3/4 and so on.

This would be the cheapest and easiest fix and if for some reason it didn't work it wouldn't eliminate the other fixes.
10-20-2012 03:52 PM
hellosailor
Re: That Darn PO!!

Tom, there are compression fittings that are designed to be installed in plastic tanks. No glue, no welding, no threading needed.

I think the link that Jimscal provided is for that type of fitting, we used to use them on chemical storage tanks and they are 100% reliable.

If you think of a plastic miushroom, with a hole running up the center of the stem and through the head? The head of the mushroom has a gasket (often a large flat gasket) under it. You put the mushroom inside the tank, pushing the "stem" through the hole in the tank wall. Then a similar gasket, washer, nut, are screwed onto the part of the 'stem" that is outside of the tank. Snug down the nut, and the tank wall is captured between the two gaskets and there's a 100% seal. Now just put your hose over the end of the stem, clamp it on, you're in business.

No need to pull the tank, just put the new fitting in the old hole, drill or ream the hole as necessary to get the sizes to match.

This is pretty much exactly the same as installing a through-hull in the hull of your boat, if you can't find plastic tank fittings, look for a small marelon through-hull and see what you can adapt from there. The tank kits will have gasket sets, etc, the through-hull will require a little more parts shopping, either way, no big deal, no need to pull the tank!
10-20-2012 11:14 AM
dacap06
Re: That Darn PO!!

Folks, thanks for your many replies. The knowledge of sailnetters is truly fantastic. I see some great advice here, and a couple of real jewels for my particular situation.

I was not aware that spin welding was a common capability. Thanks for that. Having a local firm spin weld a new fitting on the tank is greatly preferable. A special shout-out goes to Bubblehead, who gave me a firm name in Annapolis! That's less than an hour's drive from the boat. That's what I will do over the winter when I have the boat hauled in Nov.

Other techniques you mention would be equally valid but don't really work for my configuration. I do not want to permanently attach the valve with, say 5200 or epoxy as I have almost no clearance and I'd then have to disassemble the settee and knock out a tabbed bulkhead, or else ruin the tank, to remove it. Trying Teflon tape is a good idea and I already did that -- I used plumber's tape to try sealing the valve. I cannot relocate the valve. It is attached the the lowest point of a roughly triangular tank side. I'd end up with water I could not remove except by manual pump through the tank access, and I would need to cut a new hole in a tabbed bulkhead to put it in.

Regards,

Tom
10-20-2012 12:26 AM
GaryHLucas
Re: That Darn PO!!

I work with poly tanks a lot, including the Ronco's. I install fittings up to 12" in tanks up to 12,500 gallons, thats 142" diameter x 16 feet tall! Currently working on a job with 6 12,500 gallon tanks, one 900 gallon, and four 65 gallon, all of which we will install about 30 fittings into.

If the tank doesn't have an inspection port, now is the time to install one. Once you have a port big enough for the flange of a bulkhead fitting to pass through you are all set. All you have to do is trim the spin welded fitting off flush with the outside of the tank using a coarse hacksaw blade. Then enlarge the hole to take the neck of the bulkhead fitting. Use a tape measure to reach across the tank to the hole, and slide the bulkhead down the tape measure into the hole from the inside. Don't forget the gasket! Then install the nut on the outside, and your tank is now better than new, because that bulkhead is removable and replaceable if it gets damaged, unlike the spinweld fitting.

Look at Hayward or Spears bulkheads, and get the EPDM gasket for potable water. Buna is fine too.

Gary H. Lucas
10-19-2012 07:43 PM
Capt Len
Re: That Darn PO!!

Not much bonds to polyethylene . If removal of tank is not on your list , is it possible to cut an access hatch in the top and install a gasketed thruhull in the problem spot. Neoprene gasket and self tapping screws to a piece of cutting board.to seal the top. Lots of ways to skin cats but re/re still the best fix.
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