DIY Overflow: What am I doing wrong?

[paragoned]

Two weeks ago, I started reading up on all the diy overflow threads here, and decided to make myself one.
First I decided to go with the design where there's only one pipe inside the tank (and the tee decides the water level) since I wanted it to clean from the bottom. So I started building it with 1-1/4" pipe.

After testing it out, I decided I needed more flow (I'm using a Rio 17HF rated for 840gph @ 4 ft.) So I switched to the other design, with Chomper's mod. It was an easy-enough conversion... lower the tee, add more pipes, etc.

After priming, there's a clear difference in flow rates between the two designs, but I don't feel like I'm still getting enough.

Here's my reason... after the tee, the pipe connects to 3/4" hose. At first I figure, maybe I shouldn't have done that. Maybe I should've at least tee'd into TWO 3/4" hose... But then I figured, with this design, if there was some sort of constriction due to the diameter change (1-1/4 to 3/4"), then there should be a build-up of water in the vent pipe before the tee.
Either the water should just keep building up until the vent pipe overflows (or reaches the water level) or there'd be a bouncing effect (water builds up, then drains slightly faster because of the height and pressure and builds up again.)

But I saw none of that. In fact, the water didn't go any higher than the tee. It had no problem draining into the hose. Which leads me to believe that my 1-1/4" overflow isn't flowing any more water than a 3/4" overflow would.

Someone please enlighten me. I don't have a camera with me, so I can't take pictures of my overflow, but it pretty much looks like the basic design with the mentioned mod (would that affect the flow?).
A few differences would be that it's got a few more extra straight couplings (from when I switched designs) and the inside loop is about a half inch higher than the outside loop (which I understand is okay, as long as the tee is still higher than the inside loop.)

It restarts okay, if anyone's wondering.

Any ideas?

Oh, and another semi-related question. I'm to understand that it's okay to lower a centrifugal pump's flowrate through a ball valve? Does the Rio Hyper Flow count?
'Cause I remember reading in the included manual that I shouldn't restrict it in any way.

 

[Pharaoh]

The issue appears to be with restriction caused by the 3/4" tubing. The vent pipe will not fill with water as long as the "T" is lower. The deal is, the 3/4 is only allowing a certain amount of flow. The siphon on the overflow will only drain based on the amount of water flow that the smallest portion will allow. I suggest increasing the diameter of the drain hose or adding another 3/4 line.

M<ost will agree that restricting flow will not hurt a pump.

 

[CHOMPERS]

Yep, Pharaoh is spot on. Except that he didn't really mean that adding another 3/4 line was going to solve it. He meant to say that two 3/4 lines will only flow half of what one 1 1/4 pipe will.

He also meant to say that a 3/4 hose will never flow 840g on a good day even if you prayed to all the gods in Egypt... ...and all the tiki gods on Easter Island.

 

[Pharaoh]

LOL

 

[paragoned]

Yep, Pharaoh is spot on. Except that he didn't really mean that adding another 3/4 line was going to solve it. He meant to say that two 3/4 lines will only flow half of what one 1 1/4 pipe will.

He also meant to say that a 3/4 hose will never flow 840g on a good day even if you prayed to all the gods in Egypt... ...and all the tiki gods on Easter Island.

I don't know what the bigger insult is... implying I didn't know something, or implying I didn't know something that's completely false.
Many pumps' return lines (like mine for example) is 3/4". So it must be the doing of some sort of -- to reciprocate your sarcasm -- Egyptian god that's bringing all 840g of that water somehow.
And depending on your location and its system, your house's gravity fed water line will probably be either a 1" or 3/4" pipe.
So even if you tell me your house has really low water pressure, that first one should've been sufficient.

The vent pipe will not fill with water as long as the "T" is lower. The deal is, the 3/4 is only allowing a certain amount of flow. The siphon on the overflow will only drain based on the amount of water flow that the smallest portion will allow. I suggest increasing the diameter of the drain hose or adding another 3/4 line.

Then why extend the vent pipe at all? Sorry, I'm not trying to be insulting, because for the most part, you're right. And I'll probably be taking your suggestion for good measure, but the part about the vent pipe is clearly flawed. And the two of you were way too quick to dismiss half of my post.

Anyway the siphon will try and fill the outer U until the water is level with the inside U. But you're right, this doesn't happen because there's a tee draining the outer loop.
This is all assuming that the tee/drain is the same or larger diameter as the siphon, right? What I was saying was that, with the 3/4 barb, there's clearly a restriction... the tee is still draining, though not as fast as the siphon is filling the outer loop. So presumably, the vent slowly fills.

Though...not really.. the vent fills to a degree. But the added height creates enough pressure to push the water through the 3/4 barb, offsetting (albeit to a degree) the added friction of the size change. Kinda like a shower head. It bounces between low and high pressure for a bit, but eventually it finds equilibrium. And the flow inside the hose is more or less constant, except for the occasional gargling.

Anyway, thanks anyway. I figured out what was wrong.
I made a strainer that was too restrictive for the bottom mod (works fine on the surface.) So I'll be working on that.
Without the strainer though, the overflow (with the 3/4" tube) kept up with the pump. Though the pump had to be pushed back by about 10-20% based on the ball valve's lever. That's easily 600gph.

I'll probably won't test it at full power to avoid a flood. 600-700g is more than I need.

 

[basslover34]

this ought to be an interesting reply


Congrats on figuring out your problem... care to post any pics?

 

[CHOMPERS]

I don't know what the bigger insult is... implying I didn't know something, or implying I didn't know something that's completely false..

Sorry, I didn't know you were so thin skinned. I wasn't trying to insult you, nor was anything implied. I was having fun with Pharaoh, that is all.

And to be insulted because "I'm implying that you are wrong", wouldn't that make you a Know-It-All? Secondly, I wasn't implying it, I was stating it. You are wrong. You can not put that water volume through that pipe under gravity. I corrected Pharaoh, but he wasn't insulted. There was no reason for him to be.

Many pumps' return lines (like mine for example) is 3/4". So it must be the doing of some sort of....

Wow, you're really gonna be pissed at this: you are wrong. Way wrong. I'll let someone else insult you with the reason why.

 

[Pharaoh]

So, what your saying is that you had to slow down the pump in order to work with your inadequate overflow. This is all well and good, but we were trying to help you with your original design and match it to your pump so that you could have the flow to handle your pump. I do hope you have made a second overflow to account for the flow if your first overflow plugs.
The reason you had to dial back you pump is because 3/4" is not capable of flowing the water volume that you originally post that you wanted. The only reason the inlet flows at 840gph is because there is a pump behind it.

Then why extend the vent pipe at all? Sorry, I'm not trying to be insulting, because for the most part, you're right. And I'll probably be taking your suggestion for good measure, but the part about the vent pipe is clearly flawed. And the two of you were way too quick to dismiss half of my post.

No one said to extend the vent tube.

 

[Pharaoh]

Sorry, I didn't know you were so thin skinned. I wasn't trying to insult you, nor was anything implied. I was having fun with Pharaoh, that is all.

And to be insulted because "I'm implying that you are wrong", wouldn't that make you a Know-It-All? Secondly, I wasn't implying it, I was stating it. You are wrong. You can not put that water volume through that pipe under gravity. I corrected Pharaoh, but he wasn't insulted. There was no reason for him to be.



Wow, you're really gonna be pissed at this: you are wrong. Way wrong. I'll let someone else insult you with the reason why.

What...I was wrong? I thought you were translating. We're going to have to have a talk. LOL

 

[dr_sudz]

So, what your saying is that you had to slow down the pump in order to work with your inadequate overflow. This is all well and good, but we were trying to help you with your original design and match it to your pump so that you could have the flow to handle your pump. I do hope you have made a second overflow to account for the flow if your first overflow plugs.
The reason you had to dial back you pump is because 3/4" is not capable of flowing the water volume that you originally post that you wanted. The only reason the inlet flows at 840gph is because there is a pump behind it.





No one said to extend the vent tube.

bingo i have to agree with chompers and pharoh