Gravity fed pvc overflow

[SandNukka15]

So according to a few charts I've been looking at a 1.5 inch pvc is good for 1400 gph gravity fed but I've also heard they can handle more......anybody that is using 1.5 inch pvc drains what gph are you experiencing?

I wanted to use 2...1.5 inch pvc overflows for a pump rated for about 4,200 gph

 

[wednesday13]

id go with 2 2.5" pvc pipes for that gph... 1.5" will handle it but ull have alot of build up of water in the tank imo... and in return alot of drain off into the sump during matinence/power outtage... i have 3 1.5" on a tank running 1800 gph and i wish i went with bigger drains. Sure it works, but i dont like water build up in my tanks these days... larger drains help to keep a truer water level in ur tank. imo when ur tank is running u should have maybe 1/4-1/2" over the drains.... smaller drains will work but raise the water level 1-2" over ur drains sometimes. Thats alot of drain off when its shut down.

 

[SandNukka15]

id go with 2 2.5" pvc pipes for that gph... 1.5" will handle it but ull have alot of build up of water in the tank imo... and in return alot of drain off into the sump during matinence/power outtage... i have 3 1.5" on a tank running 1800 gph and i wish i went with bigger drains. Sure it works, but i dont like water build up in my tanks these days... larger drains help to keep a truer water level in ur tank. imo when ur tank is running u should have maybe 1/4-1/2" over the drains.... smaller drains will work but raise the water level 1-2" over ur drains sometimes. Thats alot of drain off when its shut down.

The drain off won't be an issue since the tank has an overflow drain

 

[SandNukka15]

The drain off won't be an issue since the sump has an overflow drain

 

[Danh]

You'll also have to be sure the sump overflow drain can drain fast enough... and in the event that the power goes out, you lose all of the extra water in your main tank to the sump drain, that when the power comes back on your sump still has enough water left in it to not run itself dry.

 

[feralhuman]

I'm basically working on this now. I have a 150 gallon tank and I'm using (2) one and one quarter lines. I definitely wish I had went bigger, probably a lot bigger. One issue I am having is the emergency overflow fairly easily starts sucking air down into the pipe and breaks the siphon, not a very good emergency backup.

 

[SandNukka15]

Personally I would rather go with multiple smaller drains then few larger ones.....I'll prob go with 3....1.5 inch drains or maybe 4