herbie drain question

Im about to move my tank and i want to upgrade my durso into a herbie. I have a 72g bowfront that has the common overflow wall with 2 holes. Ive seen a few images and explanations on google but just want to see what size pvc pipe to use for the drain lines. I was thinking 1" for the main and emergency drain and .75" for the return??

I have a 210 with two overflows, but I use 1'' in all four bulkheads. I have only had it going for a couple of months now, but already had one snail get sucked down in one pipe, and caught on the gate valve. I noticed my emergency drain dumping water, and opened the valve up and got the little guy out. I would rather have the bigger pipe with less probability of snails getting stuck and clogging it. 

3/4" as the main drain is plenty big unless your planning on an absolultely huge pump like 1300 gph. I have a 819 gph pump on my 65 and have the 3/4 gate valve closed about half due to the amount of water a full syphon will pull thru a 3/4" pipe. I have the 1" as emergency as you want it bigger in case it ever needs to be used. and you will be fine with the 1" as the return, less restriction, more flow, and more you can have the 3/4" gate valve opened up. The drain can only drain as much as the pump can push. I tested my emergency by plugging the main drian with my finger and the 1" emergency easily handled it the water and If you get the 3/4" clogged with a snail as mentioned you will know instantly as you will hear the emergency in use from the toliet flushing sound. A simple strainer on the 3/4" drain will prevent any snails anyway. Thats how I have mine set up and works like a charm, one complaint I have on the herbie is you have to maintain a pretty constant level of water in the sump or it goes out of adjustment (that is, I run mine with a trickle down the emergency for added surface skimming) and if the level of water fluctuates in the chamber the pump is in that trickle will need adjusting by closing or openig the gate on the drain. If you have an ATO that is not an issue as water level and thus all pressures are relatively constant on the pump.

Edited by Bryce - November 21 2012 at 2:44pm

I would do 1" for the drains and 3/4 for return

Better to have to much then just enough standard aquariums come with 1"

which is why I said 3/4" is plenty big on the main drain but I am not an expert by any means, and can only speak to my 1 tank, haha... if I have my gate 1/2 closed with say 550gph pumping into the display after 5ft head loss on my 819gph return in theory I could run up to 1100gph through 3/4" and since its a 72 gallon tank its more than enough. Both will work flawlessly, so it depends on your pump size, and how much you want your gate closed on the main drain, what the fittings on your pump are, if you want to reduce a 1" fitting on a pump down to 3/4" etc. I ran a 3/4" on both my main drain and return as it fit my pump, and 3/4" was easier to hide behind the tank when I ran it up and over the back. 

The first set of columns would be the minimum you would expect for the pipe size shown using nothing but gravity in a low head pressure situation to power the flow. So 660gph for 3/4" and 960gph for 1" so yea based on that chart if you plan on using a pump that pushes anything more that 660 AFTER head loss for sure go 1" - again without looking at any chart, doing any calulations of pressure, I have 550gph AFTER head loss and I have my gate on a 3/4" closed half way so obviously it can handle much more flow, but not sure your sump will, haha

Edited by Bryce - November 21 2012 at 5:27pm

IMO better to skimp on the syphon line so you have a bigger emergency drain.  3/4" will work great for a 75G tank maintaining the additional capacity in a 1" Durso, if you use the 1" as the syphon the 3/4 will have a much harder time in case of emergency.