Internal Overflow Gasket Placement

[hyperfocal]

I'm putting an internal overflow box in my tank, and am planning on having the bulkhead hold it on.. like this:

So, where should the gasket go? At "A" or at "B" or both?

Thanks much!

 

[HotHotHot]

I'd put it "A" since I don't think internal leakage from the overflow would matter much. That will seal between the box and the glass which is critical. If it matters to you, put it on both.

my 2c

Ed

 

[Sparkysreef]

<a href=showthread.php?s=&postid=6577986#post6577986 target=_blank>Originally posted</a> by HotHotHot
I'd put it "A" since I don't think internal leakage from the overflow would matter much. That will seal between the box and the glass which is critical. If it matters to you, put it on both.

my 2c

Ed

Yeah, what he said. Go with "A" I have a similar set-up. NO need to have gasket at "B"

 

[javajaws]

You need it on both. Trust me, I've done it. It'll leak through the threads if you don't.

 

[javajaws]

<a href=showthread.php?s=&postid=6579120#post6579120 target=_blank>Originally posted</a> by Sparkysreef
Yeah, what he said. Go with "A" I have a similar set-up. NO need to have gasket at "B"

Then your seal between the flange and the inside of the overflow box must be perfect. Think about it...if its not sealed there, water will leak into the threads at that point. Gasket A does nothing to prevent that water from continuing to circle around the threads and out the tank.

 

[Sohal11]

IMO. Gasket A is most of your concern. Gasket B is not necessary.

 

[ste6168]

go with gasket A and a bead of silicone in place of gasket A

 

[javajaws]

Another way to do the whole thing is to place the flange of the bulkhead on the outside of the tank...then you only need the 1 gasket...next to the flange. However, depending on the dimensions of your piping and overflow box this may or may not work for you.

 

[wife no likey]

I don't think that you want to have the internal flange of the bulkhead inside the overflow. Mount the bulkhead normally and use a threaded ell attached to an adapter possibly. This will keep the attachment of the overflow secure to the bulkhead, while maintaining the seal.

This also allows you to remove the overlow, etc.

 

[BeanAnimal]

Both gaskets would have to be used, however this is a poor design that is prone to leaking.

The correct way to set this up would be to reverse the bulkhead and put the flange side on the outside of the tank with the gasket set between the flange and tank. You can use a spacer or other gasket inside the tank to set the overflow off the back wall.

That said, If it were me, I would use an L shaped box and silicone or glue it to the back wall. My overflow is the length of my 4' tank.

Bean

 

[hyperfocal]

<a href=showthread.php?s=&postid=6582854#post6582854 target=_blank>Originally posted</a> by pennilessreefer
Mount the bulkhead normally and use a threaded ell attached to an adapter possibly.

Ahhh, excellent advice. I visited HD at lunch today and found a 90-degree male-slip and corresponding shunt that'll let me do:

I just need to drill the overflow to fit the slip on the 90-degree, and glue the shunt to the 90-degree's slip connection on the backside of the overflow box. I can cut the shunt to the right length, and it'll slide right into the slip bulkhead and hold by friction. Too easy. Thanks!

 

[javajaws]

shunt? Not following you there...Is the elbow's slip connection smaller than the bulkhead's slip size?

Do you think you'll be able to make the overflow box to elbow connection watertight? Otherwise on extended power outs you may have a problem with water draining to the level of the bottom of the hole in the overflow. Just something to look out for...

 

[javajaws]

One more thing...on that friction fit...depending on your bulkhead and actual piece of PVC it may not be tight enough to friction fit. I had this problem on my closed loop intake strainer which friction fits into 2 1.5" bulkheads. I found dabbing some PVC glue onto the outside of the PVC and letting it dry helped...it added a little bulk to make the fit a little tighter. You could also try teflon tape...

 

[BeanAnimal]

Reversing the bulkhead would be the easiest way to do this.

 

[brentp]

Hyperfocal,

Mine are just like in your last picture except I used 1" threaded strainers instead of the elbows to hold the overflows in place. I have two overflows like that and they work great. It makes it pretty easy to modify the overflows (I needed to trim about a 1/16th off of one side to make them even). The strainers also keep small snails and fish from getting in the plumbing.

Brent

 

[javajaws]

<a href=showthread.php?s=&postid=6585848#post6585848 target=_blank>Originally posted</a> by BeanAnimal
Reversing the bulkhead would be the easiest way to do this.

I would tend to agree...however depending on how big he desires his overflow box and what size piping he is using this may not be possible. When mounting the bulkhead reverse style, the non-flange side will stick into the tank a considerable amount. You then have to leave additional room inside the overflow box for the elbow.

I tried designing a box this way, but with sched 80 bulkheads and 1.5" piping the box would have been too big. By using double gaskets and putting the flange inside the box I was able to get the box down to 4" from front to back with a 1.5" elbow in there that can be removed for cleaning.

And don't think about cutting down a normal threaded sched 80 bulkhead to make the reverse style take less space (tried it)...because the threads are threaded with a pipe taper and you would have to re-thread the bulkhead to be able to effectively use the threads. If you have a slip bulkhead (on non-flange side) this might work for you though. Another option is to try out a "shorty" bulkhead.

Hope this helps.

 

[JR719]

I agree with BeanAnimal with putting the gasket on the outside of the tank, at least that is how I read it. If you have water seeping thru other fittings inside the tank, the water only stays in the tank. Seal the area where it leaves the tank and no leaks to the outside.

 

[hyperfocal]

<a href=showthread.php?s=&postid=6585483#post6585483 target=_blank>Originally posted</a> by javajaws
shunt? Not following you there...Is the elbow's slip connection smaller than the bulkhead's slip size?

Do you think you'll be able to make the overflow box to elbow connection watertight? Otherwise on extended power outs you may have a problem with water draining to the level of the bottom of the hole in the overflow. Just something to look out for...

Here are the parts I'm thinking of using (the acrylic is scrap, I'm not that bad a craftsman ):

The hole in the acrylic was drilled to fit the narrow part of the 90-degree. That part passes through the hole and will be glued into the PVC male-male connector (what I referred to as a 'shunt' in a previous message). I'll seal the PVC->acrylic joint with Weldon #40. It'll end up looking like this:

As it turns out, that PVC connector isn't perfectly cylindrical, it is slightly tapered -- one end fits snugly into the slip bulkhead, the other fits loosely. When I do the final assembly, I'll trim it to a better length... I just have to remember to trim off the narrow end so it'll friction-fit the bulkhead

 

[javajaws]

OK, so it looks like you are using a smaller sized elbow on a larger bulkhead? I just couldn't figure out how you would use a coupler (what you call a shunt) if the elbow and bulkhead were say both 1"

It looks like that will work for you, but I'd still be carefull about the water leaking into the bulkhead from around the friction fitting. The only time you'll have to worry about it is during an extended power outage (because it'll just be a slow drip if any). Also, you would be surprised how loose a friction fit can get when it is underwater...make sure you test for that. Wouldn't want it coming loose when filled!

 

[tack-msv]

I went through this very same situation. I tried just about all of the solutions mentioned up to this point. In order to make the overflow most flexible (being able to change and evolve according to your needs), you should go with your first diagram and put gaskets at both spots. If you go with your shunt idea, you are restricting your overflow capacity from 1" to 3/4", as your 90 slip/street elbow has to be able to fit into the 1" shunt. This will cut down the overflow from 600gph to around 400gph (need to check one of the flow calculators links to get exact gph). If you use a 1" 90 slip street that goes straight into the bulkhead without the shunt, you wont restrict the overflow, but the friction fitting will continue to leak down to the lowest point of the bulkhead in the overflow box during a lengthy power outage, just as mentioned in previous posts. Most likely leading to a flood (unless you account completely for drainage capacity into your sump). I finally went with a gasket at "B" and siliconed the entire box to the aquarium (like Bean's suggestion). This was a PITA because the tank was up and running and I had to drain the tank down and place all corals below the water line and not use the overflow for two days while the silicone dried. My corals looked rough for a few days afterward, but all is fine now.