Herbie Overflow Emergency Size

[joobie]

Hi All,

I'm in the process of putting together a Herbie Overflow - the one with a siphon with a gate value and an extra overflow to handle any excess / emergency overflow.

I have a 30gal tank and have gone with 3/4" pipe work for both the return and the main siphon and emergency overflows. Currently my tank is with a Glacier, getting drilled for the bulkheads to fit.

So that I can sleep the next few nights whilst I wait for the tank to come back, is using 3/4" pipe work for both the main siphon and emergency overflow OK, given that the return is 3/4"? I read some posts where people use a larger emergency overflow "just in case", but I opt'ed not to use this to try to keep the aesthetics of the tank by using as small as possible pipework.

My logic is based on the thought that the return is only 3/4", so if I had the main siphon at 100% open with the gate valve, this in theory should accommodate the entire return flow. In the event the main siphon blocked, the emergency would also be able to take 1:1 the return volume of water.

Is this logic flawed?

Also can someone explain why most Herbie references say that some water will overflow out the emergency / 2nd overflow pipe? If the main siphon is equal to or greater than the return, why would this occur?


Thanks, Richard

[dava6711]

Hi All,

I'm in the process of putting together a Herbie Overflow - the one with a siphon with a gate value and an extra overflow to handle any excess / emergency overflow.

I have a 30gal tank and have gone with 3/4" pipe work for both the return and the main siphon and emergency overflows. Currently my tank is with a Glacier, getting drilled for the bulkheads to fit.

So that I can sleep the next few nights whilst I wait for the tank to come back, is using 3/4" pipe work for both the main siphon and emergency overflow OK, given that the return is 3/4"? I read some posts where people use a larger emergency overflow "just in case", but I opt'ed not to use this to try to keep the aesthetics of the tank by using as small as possible pipework.

My logic is based on the thought that the return is only 3/4", so if I had the main siphon at 100% open with the gate valve, this in theory should accommodate the entire return flow. In the event the main siphon blocked, the emergency would also be able to take 1:1 the return volume of water.

Is this logic flawed?

Also can someone explain why most Herbie references say that some water will overflow out the emergency / 2nd overflow pipe? If the main siphon is equal to or greater than the return, why would this occur?


Thanks, Richard

Because you can never, exactly match the flow rate from your return pump with the gate valve on your full siphon standpipe, so most people finely tune the gate valve ever so slightly, so a little excess water trickles down the emergency standpipe, this method makes the system pretty much silent.

I would go with 1" pipe work for your emergency standpipe just the extra piece of mind, but 3/4" will still work for you!

[Lukel]

Also can someone explain why most Herbie references say that some water will overflow out the emergency / 2nd overflow pipe? If the main siphon is equal to or greater than the return, why would this occur?


Thanks, Richard
From years of expierience with the Herbie.... i can tell you that there is always a little trickle down your emergence drain, becuase you can't dial the main to be exact... it seems to change just a little bit in the coarse of a day... and your herbie might start to make noise and gurgle and crap.... tune it as close as you can and let the emergency take a very very slight trickle...

as for your size question, how many gallons per hour is your return pump.... after head loss and such...

[Crusinjimbo]

Got a 60 cube and 20 sump with a 3/4 drain, 1" emergency drain and an Eheim 1260 return. The drain gate valve is running 90% open, the return pump is wide open and just a slight flow in the overflow. Dead silent! You didn't say what return pump you plan but it sounds like you will have to choke the drain way back to keep sump flow reasonable and placement of the gate valve might be critical to the sound level. I believe I have read that the drain valve will be more quiet if located closer to the drain exit into the sump. I roughed my in the garage until I got everything quiet before gluing anything.

[sleepydoc]

the part of the equation you forgot was that the return flow will be under higher pressure (from your return pump) than the overflow drain and so will potentially carry more flow than a simple gravity fed pipe. It depends on what your return pump is, but I would consider increasing the pipe to at least 1"

[joobie]

Thanks Guys.

Interesting point RE the pressure on the return increase the overflow - make sense.

My issue is that the glazier has the tank at the moment and has either started drilling or is soon to drill it. I can put an amendment in (maybe), but thinking if there are any other alternatives..

I was looking at getting the Eheim Compact 300 (http://www.aquariumproducts.com.au/catalogue_products.php?prodID=6095&catID=13) which has a 12mm output (.47"). Given my tubes are all 3/4", would it still be a risk if I ran 3/4" pipework?

My thought process is that the output from that pump is 1/4 less than the 3/4" pipework, so there is actually 1/4 additional volume in the 3/4" to compensate for the increased pressure.... is this view flawed?



Thanks :)