Overflow question

[bh750]

Ok so theoretical question here...

I have an overflow in my tank with a hole that measures 3/4" in diameter...

my overflow pipe is 1" pvc. And the pvc on the otherwise of my overflow, the bottom of the tank, is also 1" pvc.

Does it matter if the pvc is 1" (or larger for that matter)? Meaning the narrow 3/4" section will restrict flow enough that it doesn't matter how large in diameter the pvc is on either side, it will restrict the flow as if the whole run is 3/4"

Hope that makes sense. All along I was thinking my overflow plumbing was 1" when in reality it's flowing like it's 3/4"

 

[blaxsun]

For the most part, yes. Although if it's a very short 3/4" distance you'll probably see a bit more flow than if the entire pipe was 3/4" just based on the additional weight of water pushing down.

 

[KStatefan]

Ok so theoretical question here...

I have an overflow in my tank with a hole that measures 3/4" in diameter...

my overflow pipe is 1" pvc. And the pvc on the otherwise of my overflow, the bottom of the tank, is also 1" pvc.

Does it matter if the pvc is 1" (or larger for that matter)? Meaning the narrow 3/4" section will restrict flow enough that it doesn't matter how large in diameter the pvc is on either side, it will restrict the flow as if the whole run is 3/4"

Hope that makes sense. All along I was thinking my overflow plumbing was 1" when in reality it's flowing like it's 3/4"

It will not restrict it like the whole run is 3/4" since the larger portion will not have as much friction reduction.

 

[Jedi1199]

For the most part, yes. Although if it's a very short 3/4" distance you'll probably see a bit more flow than if the entire pipe was 3/4" just based on the additional weight of water pushing down.

It will not restrict it like the whole run is 3/4" since the larger portion will not have as much friction reduction.

Both of these replies are correct, and not correct at the same time.

Depending on your setup, and since most systems do dot drain in a straight line down, here is what you have.

The water weight will cause an increase of pressure rate as it passes through the restriction. Once it enters the larger pipe on the other side, it will reduce pressure to less than what it would be if the whole run was the same size.

There is a lot of physics and hydrodynamics that are involved in the full explanation that honestly have no impact on your issue.

The simple answer is "yes". Reducing your drain from 1" to 3/4 " does impact your overall flow rate. Does it matter to your system? No.

 

[blaxsun]

Both of these replies are correct, and not correct at the same time.

Thanks for clarifying that in more detail!

 

[NowGlazeIT]

No matter the other sizes your smallest fitting will limit your flow to the specs of that fitting’s size.

 

[bh750]

Thank you all so much for the replies! I'm inclined to go with what Jedi1190 said. Flow loss at the one constriction point. But flow before and after that point will be better. So I'll continue with what I have now: 1" pvc before and after the 3/4" bulkhead. Rather than 3/4" the whole run.