Herbie overflow bulkhead/pvc sizing question

[wun]

tl/dr: I am running an herbie overflow, I have 3/4 inch bulkheads(that I cannot replace), but am interested in running 1" pvc piping to increase my flow. Will this increase the flow at all(even slightly?), or will this 1" pipe make it harder to create a siphon due to the 3/4 inch bulkhead chokepoint? Would it be beneficial to use 1" pvc above the bulkhead in the overflow and 3/4 inch pvc after the bulkhead?


Hey Everyone, I have been lurking here for the past 2 months researching on how to build my first reef tank, and its all about to come together. I am just running into one question I was hoping I could get answered. First here is some info on my set up:

I have a 55 gallon "tall"(dimensions are somewhere around 36" across, 22" tall, 18" deep), this sits on a stand about 3 feet tall. I am trying to set up a herbie overflow. I have a corner overflow purchased from my local pet store. The tank was pre drilled with 2 holes when i bought it, sadly these holes will only fit 3/4 inch bulkheads, so 3/4 inch pvc piping is what I have attempted to use. I have a 10 gallon sump(all I can fit, it will have to do), an eshopps 120 protein skimmer, and a 4.0 sicci return pump. Lastly I have about 4 feet of spa flex from the pump to the top of the tank. If there is any more info that may be needed let me know

SO now here lies my issue: When i went to set all this up, my return pump's flow was much more than the flow from the 3/4 bulkhead/pvc piping. I had this set up properly as far as herbies go, however the pump was going so fast I couldn't really mess around trying to get a siphon. I have now throttled the return pump by adding a gate valve, however I haven't tested this out yet because I wanted to post this question here first. Will using 1" pipe, despite my 3/4" bulkheads, help increase flow at all?(even slightly?), or will this 1" pipe make it harder to create a siphon due to the 3/4 inch bulkhead chokepoint? Would it be beneficial to use 1" pvc above the bulkhead in the overflow and 3/4 inch pvc after the bulkhead? I have had trouble finding exact answers to this question. I thank you all for any help in advance!

 

[Lsufan]

Welcome to RC !!!

The flow will be based on your bulkhead so upsizing the pipe will not get u any more flow. It also wouldn't hurt anything using all 1" pvc on your 3/4" bulkheads. Depending how u intend to run the herbie it may make it a little quieter using 1".

The emergency drain on a herbie is really supposed to stay dry. If u run it this way then I don't think it will make a difference. Even though the emergency is meant to stay dry I know a bunch of people have a small trickle they let drain down the emergency because they don't have to mess with the valve on the syphon as much. If u plan on having a trickle in the emergency then using 1" pvc may make it a little quieter then using 3/4".

To answer your second question, the syphon will work just fine if u decide to use 1" pvc. Just don't expect it to give u any more flow.

It won't hurt anything having a valve on your return pump. Depending on your head loss u would probably need one anyways with that return pump & only a 10 gallon sump. Otherwise u would have a lot of water moving through that 10 gallon. It's not ideal, but a 3/4" syphon should handle the flow u need on your setup.

When u start it up make sure the valve on the syphon is all the way open, then slowly close it until u get it stable & the water in the overflow box is the hieght u want it.

 

[ca1ore]

How much flow are you aiming for that a 3/4" siphon cannot keep up? For a 55, you should be shooting for 350 gph, which the siphon should be able to match. Replacing a run of 3/4" with 1" pipe will increase flow a bit, though the 3/4" bulkhead constraint will limit that gain.

 

[wun]

Thank you both for your replies! I am trying to get around 400-500 gph for flow. I think my first issue with the very slow flow through the 3/4 inch pipes was being caused by my 3/4 inch gate valves. For whatever reason, the gate valves I had reduced the inner diameter of the valve at the gate mechanism. It would connect to 3/4 inch pipe, but at the actual gate mechanism the inner diameter was like the size of a button, weird right? They were labeled as stop valves at ace hardware. I now have the normal gate valves where the inner diameter is the same all the way through.

My plan is to use 1 inch pipe in my overflow, connect that to the 3/4 inch bulkhead, and use 3/4 inch pvc pipe under the tank to the sump. I read on another forum that using 1 inch pipe after the 3/4 inch bulkhead would probably cause a gurgling noise, which makes sense to me. I finally have all the pipe fittings in front of me, so hopefully by tonight I will have some fresh water running through the tank to test it all out!