3/4 in drains for 125?

coralosity351 · Feb 13, 2017

My returns are 3/4 can i use the same for the drain or go bigger?

CastAway · Feb 13, 2017

Much bigger, depending on some variables.

I have two 3/4" returns and a 1-1/2" drain on a 150, and have to by-pass some of the return to keep from overflowing.

TheEngineer · Feb 13, 2017

It depends on your desired flow rate and the style of drain you are using. A siphon will flow much more water than an open drain (herbie vs durso for example).

jgvergo · Feb 13, 2017

TheEngineer said:
It depends on your desired flow rate and the style of drain you are using. A siphon will flow much more water than an open drain (herbie vs durso for example).

I have a Bean Animal with 1" pipe, BUT my sump is 10 feet below the tank which seriously increases the flow of the siphon.

malira · Feb 13, 2017

coralosity351 said:
My returns are 3/4 can i use the same for the drain or go bigger?

You will have to go bigger. You can push more water through a pipe than gravity can pull. So if they are the same size you can overwhelm the return and you tank will over fill.

How much return turn over do you plan on having? A 3/4 inch return will have a limit for your flow. Mine was around 650 gph. I couldn't push any more than that. My pump was rated at 1200 gph for the head pressure I was at.
I am going to up grade to 1 1/4, I already have a 1 1/2 drain.

Bdog4u2 · Feb 13, 2017

Bigger. nothing like a snail taking cruise down your drain and plugging it up

coralosity351 · Feb 13, 2017

malira said:
You will have to go bigger. You can push more water through a pipe than gravity can pull. So if they are the same size you can overwhelm the return and you tank will over fill.

How much return turn over do you plan on having? A 3/4 inch return will have a limit for your flow. Mine was around 650 gph. I couldn't push any more than that. My pump was rated at 1200 gph for the head pressure I was at.
I am going to up grade to 1 1/4, I already have a 1 1/2 drain.

My pump is rated about the same my returns are on either end of the tank both 3/4 pipe

coralosity351 · Feb 13, 2017

So can my drain then be 1 or do i really need 1.5?

TheEngineer · Feb 13, 2017

Again, what is your expected flow rate?

amps · Feb 13, 2017

coralosity351 said:
So can my drain then be 1 or do i really need 1.5?

I'm pushing about 1400 gph through a 1.5" herbie setup. I really really wish that I had plumbed 1" drains instead. I've had to close my gate valve almost 80% to match the flow and it's created a much larger chance of blockages.

coralosity351 · Feb 13, 2017

TheEngineer said:
Again, what is your expected flow rate?

About 1200 gph

TheEngineer · Feb 13, 2017

Each 3/4" drain, assuming a 24" drop with the pipe submerged in the sump, will run about 935gph. If you are running two 3/4" drains, you should be just fine and it would allow you to close them down slightly to adjust to your actual flow.

EDIT: This is at full siphon, not using a Durso. Durso will flow less.

coralosity351 · Feb 13, 2017

Ok awesome sounds like a plan

CastAway · Feb 14, 2017

coralosity351 said:
Ok awesome sounds like a plan

So just to clarify, are you planning a full syphon, or, a gravity drain? Did I miss that?

Roy 9121 · Feb 14, 2017

jgvergo said:
I have a Bean Animal with 1" pipe, BUT my sump is 10 feet below the tank which seriously increases the flow of the siphon.

I'm so jealous of you guys with basements.

Roy 9121 · Feb 14, 2017

CastAway said:
So just to clarify, are you planning a full syphon, or, a gravity drain? Did I miss that?

Whether it's a siphon or a gravity drain is very important. Either way though, the drain needs to be larger then the return.

cilyjr · Feb 15, 2017

Roy 9121 said:
Whether it's a siphon or a gravity drain is very important. Either way though, the drain needs to be larger then the return.

Why exactly? I'm not saying it might be a good course of action but NEEDS to be?
Would not the pump output regulate the drain size requirement?

Let's say we have a tank with just 2 3/4 lines (for simplicity's sake. We want emergency pipe ect in the real world). The 3/4 drain at full siphon and the 3/4 return has a tee to adjust flow back toward sump (or maybe a controllable flow pump).

TheEngineer · Feb 15, 2017

cilyjr said:
Why exactly? I'm not saying it might be a good course of action but NEEDS to be?
Would not the pump output regulate the drain size requirement?

Agree. That was my point asking about flow rates. Having 3/4" returns doesn't matter if you are running a MJ1200 on them

vertigo01 · Feb 15, 2017

X2. Seeing as most pumps are throttled back so as not to overwhelm the overflow, why would the overflow size make such a diff?
If the return is corrected for the overflow, couldn't 1 theoretically use 1/2 main and 1/2 emergency and still be safe from an overflow situation? Using a full siphon of course.