Plumbing size on 20 gallon frag tank

[fishybizzness]

Hi everyone,
I'm in the process of setting up a 20 gallon long frag tank. It will be fed off of a manifold from the return of my display tank. The overflow will be a acrylic internal overflow box that I will silicone to the inside of the tank peninsula style. The return will be on the opposite side of the tank. I an planning on drilling two 1/2" bulkheads to run a herbie style overflow. I also plan on doing a 1/2" return line. My question is will the two 1/2" overflow lines and the 1/2" return be enough for this size tank? Thanks for the advice!

 

[fishybizzness]

No ideas anyone?

 

[fishybizzness]

Heelllooooooo!! Anyone there???

 

[ScottieB]

Sorry about the late reply.
1/2 inch seems a little small but if your connecting to your sump/DT via the manifold then it will prob be fine. Your turnover through the frag tank won’t be that high but it doesn’t necessarily need to be. Likely just supplement the flow with power heads.

With that said, Unless you have a bunch of spare 1/2 PVC laying around I would prob use 3/4 or 1 inch and adjust intake down to achieve your desired turnover. That would give me more flexibility and I would feel better having a larger diameter emergency drain.

 

[fishybizzness]

After some thought, I'm going to go with a 3/4" main drain and a 1/2" emergency drain. I'm still contemplating whether to go with a 1/2" or 3/4" return line. I could go either way because the manifold off the display tank return line that I'll be tapping into is a 1" so I will have to reduce it. What are your thoughts on the return line size?

 

[ScottieB]

Understood, sounds like a good plan on the drains. The returns could be either, honestly if you have some 1/2 laying around use that, considering your coming off a 1 inch manifold I think you could technically go either way.

I think it’s easier to find more PVC parts, options in 3/4 in my area at least, so that might sway my decision. But honestly it’s just about getting water into and out of that frag tank so both options would work. Your still likely to supplement flow either way.

 

[fishybizzness]

Thanks for the help! And yes, I will be using a flow pump of some kind to have good flow in the tank.

 

[Reeferdood]

Good rule of thumb is to oversize the drains. Anything that is smaller than 3/4 will almost always have some sort of issue at some point, or from the get/go...

 

[smartwater101]

After some thought, I'm going to go with a 3/4" main drain and a 1/2" emergency drain

If anything the emergency should be the larger PVC! As mentioned, you don't necessary need the turn-over rate since the overall flow-rate will be from power heads. But your emergency should always be able to handle what your main drain can handle, if not more. Redundancy ftw. Better safe than sorry.

 

[fishybizzness]

Good point! I hadn't thought about that! The only problem is that the overflow box only has about 1 1/2" clearance between it and the glass. I ordered a low profile screen insert for the 3/4" and was using a 12" street elbow with a short piece of pipe facing upwards for the emergency. Do you think it could work if I used a 1/2" for the return? I'm limited on options because of the depth of the overflow box and am trying to figure out something both effective and safe at the same time. Thanks

 

[smartwater101]

Unless the box isn't long enough, the distance in-between should be fine for 3/4.

 

[fishybizzness]

This is the type of overflow I'm using. The holes for the overflow will be drilled through the side of the tank so I would have to come off the bulkhead with a 90° fitting. It's kinda tight on space in the overflow box to fit a 3/4" 90°. I've also attached the overflow screen I ordered. Thanks for the advice!

 

[smartwater101]

I think i c. So it needs enough space for a corner PVC and whatever little bit of space the bulkhead takes up... hmmm that is tricky...

like this?

The box you have may not have enough space for this. Any chance you can return for a larger one? Also, I'm not sure I understand what the round screened bulkhead is for. The barbed box is where the water runs into. ... unless you're trying to used the barbed box on the outside... in which case definitely no no. That's not how its meant to be used.

 

[fishybizzness]

I'll try to explain. The 1/2" and 3/4" overflow holes will be drilled side by side. The bulkheads will be installed. The round screen will be on the 3/4" bulkhead that will be the main drain. I am doing that because a 3/4" 90° won't be able to fit in the box. It will have a gate valve on the outside to try and get a full siphon. The 1/2" emergency will have a 90° street elbow out of the bulkhead inside the overflow box facing up with a small piece of pipe to raise the water level in the box. I can't return the overflow box because I bought it several months ago on Ebay. I was contemplating whether to use a 1/2" or 3/4" return but as was pointed out earlier, the return shouldn't really be bigger than the emergency.