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View Full Version : Pipe thread variations? Problem capping an overflow pipe.


TimTheWiner
04/11/2017, 12:52 AM
So I just picked up this 92 gallon corner acrylic on CL for a decent price, just a few scratches that need addressing. I want to fill with water for some time in my garage to do a leak test, but first need to call the FIVE feed/return lines. Not sure why so many. Anyhow, 3 are in the rear corner overflow, two in the bottom of the tank. I have capped them all with teflon tape on the threads, however I seem to be having trouble with a larger black fitting on the rear underneath. The outside of the male threads is 1.5" diameter, but when I tried a 1.5" cap it was too large. Went back for a 1.25" threaded cap which seems the right size, but as gently as I start to thread it, it seems to tight almost stripping feeling after just a few rotations. I don't want to strip the threads if the cap is incorrect and then have leaking. I assumed everything is NPT threads, but could it be something different? Last pic is just the tank set up from seller. https://uploads.tapatalk-cdn.com/20170411/1d8fb3acf6f4578afcb049e4d8ff2431.jpghttps://uploads.tapatalk-cdn.com/20170411/0a670a813feba828980c2be0919c8d8e.jpghttps://uploads.tapatalk-cdn.com/20170411/3045a0f392007e145452578a64c6905f.jpghttps://uploads.tapatalk-cdn.com/20170411/4619373bef14f8a3af21ef8f07394482.jpg

tkeracer619
04/11/2017, 01:05 AM
The outer threads are for the nut only. You won't be able to thread on any fitting. Only internal threads or slip fittings are standard pipe fittings.

Also, consider using teflon paste instead of teflon tape. Teflon tape isn't idea for plastic fittings.

I would not re-use the bulkheads.

TimTheWiner
04/11/2017, 01:12 AM
Thanks for the clarification. Do you think the teflon tape on the other 4 inside threaded plugs I did should be find temporarily. Only really want to fill the tank for a few weeks then drain to check for leaks in the tank itself, I can't imagine it's too common with acrylic unless there is an evident crack.

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TimTheWiner
04/11/2017, 01:19 AM
Just not really sure how to call that one now. No inside threads. Only option may be cut the PVC up towards the top where it overflows.

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Ron Reefman
04/11/2017, 08:26 AM
Slip in a piece of pvc pipe inside the tank and make it long enough that it sticks out the top of the tank. Make sure it's a good snug fit in the bulkhead.

sleepydoc
04/11/2017, 08:33 AM
+1 to Tkeracer's comments.

As s/he said, the outside threads on bulkheads are for the bulkhead not only. Connection to your plumbing is made on the inside of the system.

Bulkheads come in threaded and slip connections. If there are no threads on the inside then it is a slip connection that needs to be glued. Many people ask about leaving the slip fit connections unglued. My general advice on that is that if you would care if the connection completely broke apart at 2 in the morning then it should be glued (i.e. anything external to the tank or that would cause catastrophic flooding)

If it's threaded, you can try using teflon tape but thread sealant is a better choice. Regardless, you need to be careful not to over tighten. NPT connections are tapered, so the end of the pipe is slightly narrower than the point at where the threads stop at the body of the pipe. This means that as you tighten it further it puts more outward pressure on the female connection and you can easily crack or split an ABS bulkhead. Teflon tape doesn't seal as well as paste, so you tend to see this more when people use tape.

Completely agree with replacing the bulkheads. If you just need to check the tank for leaks, you can probably get by, even if the bulkhead seal isn't perfect. You'll presumably be doing this in a garage or someplace where a leak won't be catastrophic.

TimTheWiner
04/11/2017, 09:22 AM
I have used three purple multi cement or many home ABS projects so that's something I'm comfortable and familiar with. The other 4 caps I DID use channel locks when tightening them but mainly because of the bulk that the teflon tape added just made it is little easier to tighten. I am curious if I replace all the bulkhead tubes before doing my final setup, how the heck I'll get into the bottom of the tank at the rear overflow. May require some specialized tool like an extra long basin wrench to hold the top in place while the bottom nut gets tightened from the other side.

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Potatohead
04/11/2017, 09:40 AM
Need to use slip PVC into the bulkhead, then a cap on that piece.

TimTheWiner
04/11/2017, 09:47 AM
Maybe for piece of mind I will back out the threaded plugs that I put tape on and apply the sealant instead. Any recommendations between these 3, or another? https://uploads.tapatalk-cdn.com/20170411/aa280d1f395a6b4d3b9473eaa4af91f3.jpghttps://uploads.tapatalk-cdn.com/20170411/eb7d15079bf80ea7b476f1367b31d046.jpghttps://uploads.tapatalk-cdn.com/20170411/d552145f2e235d8cdca57646e9c2d509.jpg

tkeracer619
04/11/2017, 10:51 AM
I am curious if I replace all the bulkhead tubes before doing my final setup, how the heck I'll get into the bottom of the tank at the rear overflow. May require some specialized tool like an extra long basin wrench to hold the top in place while the bottom nut gets tightened from the other side.

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You really never want to move a tank with a bulkhead in place. All it takes is one bump to crack the tank.

When you put the new bulkhead in place the rubber gasket goes on the flanged side. Flange > Gasket > Tank > Nut. The gasket will keep the bulkhead from rotating. You want to go hand tight with the nut and then maybe 1/4 turn with a wrench.

Here is a thread I posted that has some tips.
http://reefcentral.com/forums/showthread.php?t=2630567

tkeracer619
04/11/2017, 10:55 AM
Maybe for piece of mind I will back out the threaded plugs that I put tape on and apply the sealant instead. Any recommendations between these 3, or another?

Tru Blu is what I use.

If you used the internal threads then that is fine. If you used external threads then you will want to use the internals or glue in a plug.

For the one you were initially questioning I would simply glue in a plug. That bulkhead is already trash just by looking at it. I would never re-use a bulkhead.

I have always used CPR brand bulkheads with great success but GimpyFin recommended the Reef Octopus ones in that thread I posted above. They sound very promising.

TimTheWiner
04/11/2017, 01:07 PM
Wow, I guess I'm lucky I didn't crack the acrylic during transport. Maybe instead of capping the old bulkheads and test filling I should just decidd how many feeds/returns I will need and put everything new before I do a test fill so I'm start with a clean slate.

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tkeracer619
04/11/2017, 02:19 PM
Definitely got lucky there!

The setup likely had what is called a "herbie" drain setup.

One drain (the smaller one) is in full siphon drain and does most of the drain capacity. This drain has a valve on it that you reduce until it slows that drain down such that it barely doesn't keep up. The water rises in the overflow until it gets to the emergency drain (which also sets the water height inside the overflow box). Keeping the emergency drain wet keeps a constant water level in the overflow box and makes tuning the siphon drain easy.

The other bulkhead is the return from the sump.

Looking at the front of the tank as you would if it was full and you are viewing it... I would guess the furthest back is the return, the one on the right is the full siphon, and the one on the left is the emergency.

As for the two on the bottom I probably wouldn't use them. Measure the hole size and use a sch80 bulkhead instead of the ones that are there. If this seal fails the entire content of the tank dumps to the ground.

I just setup a tank that had 5 holes in the bottom of the display. Since it was glass I used equal thickness plate glass and covered them permanently. You could do the same with some weldon and pieces of acrylic (silicone doesn't work on acrylic). How you go about it would be up to you but I am always hesitant to have bulkheads in the bottom of the display area.

TimTheWiner
04/11/2017, 03:43 PM
Yes, I really think I only need the rear overflow. I don't love the idea of just caps on the details visible from the front/bottom side. Perhaps I could use the weldon acrylic method with a piece on both top and bottom for added piece of mind. From one it looks like from the top, the is one overflow line and 2 return lines, but I am the newb. I can post a pic from the top when I get hold from work.

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TimTheWiner
04/11/2017, 03:47 PM
Aside from the bulkheads should an acrylic be any more or less prone to leaks (ie: at seams) than glass. I hear bow/curved glass tanks have a tendency to leak more but not sure if that's true with acrylic since no silicone at the corners.

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tkeracer619
04/11/2017, 04:00 PM
It's all the same in regards to leaking. Both will blow out if on an improper surface. The bottom needs to be in plane. As soon as the bottom is twisted the chance for failure rises.

Each manufacturer has their own set of requirements as to what a proper stand surface is.

CK00020
04/11/2017, 05:16 PM
+1 on the tru blu, same company makes a yellow #5 that is good too

TimTheWiner
04/12/2017, 12:34 AM
It's all the same in regards to leaking. Both will blow out if on an improper surface. The bottom needs to be in plane. As soon as the bottom is twisted the chance for failure rises.

Each manufacturer has their own set of requirements as to what a proper stand surface is.

Not sure I'm getting this. How wouldn't it be in plane? You mean like a warped surface? I can't imagine the surface of the stand itself not being perfectly level. The flooring underneath will be hardwood, it is handscraped so had small grooves in it.

tkeracer619
04/12/2017, 01:03 PM
Yes, the surface of the stand needs to be in plane. If you twist the tank the seams are the first thing to go. Typically you shim the bottom of the stand to level the whole thing.

TimTheWiner
04/12/2017, 06:28 PM
Ok, I'll make sure to shim if needed. On the note of capping the 2 holes in the bottom center of the tank, not the overflow, I DO think I will wake up permanently call these via acrylic and weldon. I don't see needing more than the 3 lines in the back corner of the overflow.

•Would it make sense to put a piece of acrylic both on the inside and underside of the hole? How thick should the acrylic be and how far should I overlap the edge? After this is done can I also use silicone or another sealant on the edges?

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