HELP: Overflow selection and Return Pump

[Danh Ngo]

Setting up an HOB overflow box and return pump from sump
The stand is 38” high + 22” tank high -> roughly 5ft high
Overflow : ESHOPP PF-800Gph for 70G tank
Question on return pump: Should I choose oversized pump?
The height will effect the power, what pump should I use
Return pump:
SYNCRA SILENT 4.0 PUMP (951 GPH)
SYNCRA SILENT 5.0 PUMP (1321 GPH)
Or any other recommendation
Below is the speed of pump associated with the height

 

[WWIII]

If you're looking specifically at those pumps, which are good return pumps, I would go ahead and get the 5. You can always run a t off of the maim return line with a valve going back into the sump and redirect some flow if needed. The syncra 4 is probably just a bit undersized if you're going for near 700gph.

 

[WWIII]

If you're looking specifically at those pumps, which are good return pumps, I would go ahead and get the 5. You can always run a t off of the maim return line with a valve going back into the sump and redirect some flow if needed. The syncra 4 is probably just a bit undersized if you're going for near 700gph.

 

[mfinn]

If it were me and those were the only 2 pumps available, I would get the 4 and a good valve.
On a 70 gallon tank you really don't need any more than 350 gph return in the tank. ( counting height and fittings for headloss).

 

[Danh Ngo]

If it were me and those were the only 2 pumps available, I would get the 4 and a good valve.
On a 70 gallon tank you really don't need any more than 350 gph return in the tank. ( counting height and fittings for headloss).

But then the return pump is way less than the overflow?
For a 70 what size overflow is good?

 

[WWIII]

But then the return pump is way less than the overflow?
For a 70 what size overflow is good?

The overflow should work fine with the smaller pump. I was assuming you were trying to go for 10x turnover for triton or something similar. I agree with mfinn if that's not the case! I think somewhere around 5x turnover is good for most display tanks and sumps personally. The overflows generally list the maximum gph possible, in this case 800 gph, so that people know how much flow they can handle at the top end. If you were to go with a pump over the 800gph, the overflow wouldn't be able to handle the amount of flow and the water level in the display would be really high, if not overflow, unless you choked dowm the return pump or replaced with a smaller one.

Having said all that, there is no reason the pump gph has to match or even be close to the overflow gph. It surely will do just fine with anything lower than 800gph, even down to a couple hundred gph.

 

[Retro Reefer]

For what it’s worth I have found running HOB overflows near their max flow rating helps keep air bubbles from building up in the U tube.. I’m planning my next build and will be using the pf-300 (rated at 300 GPH) on a 40 gallon tank and I plan on pushing around 250-275 GPH through it, probably going with controllable DC pump so I can adjust output without the need for valves.

 

[mfinn]

But then the return pump is way less than the overflow?
For a 70 what size overflow is good?

You do not need to try and match a overflow with a return pump.
The main thing is not getting a return pump that is more than the overflow can handle.

Have you considered buying a overflow drill kit and skipping the hang-on back overflow.
They are very easy to do, not that expensive, and once drilled, you never have to worry about losing the overflow siphon like you do with a non drilled overflow.

 

[Danh Ngo]

You do not need to try and match a overflow with a return pump.
The main thing is not getting a return pump that is more than the overflow can handle.

Have you considered buying a overflow drill kit and skipping the hang-on back overflow.
They are very easy to do, not that expensive, and once drilled, you never have to worry about losing the overflow siphon like you do with a non drilled overflow.

I like making changes, so I try not to drill the tank. I know that type of overflow would be much better

 

[Danh Ngo]

You do not need to try and match a overflow with a return pump.
The main thing is not getting a return pump that is more than the overflow can handle.

Have you considered buying a overflow drill kit and skipping the hang-on back overflow.
They are very easy to do, not that expensive, and once drilled, you never have to worry about losing the overflow siphon like you do with a non drilled overflow.

I’m thinking about adding a ball valve for the return, could it slow down the return pump a?

 

[Danh Ngo]

The overflow should work fine with the smaller pump. I was assuming you were trying to go for 10x turnover for triton or something similar. I agree with mfinn if that's not the case! I think somewhere around 5x turnover is good for most display tanks and sumps personally. The overflows generally list the maximum gph possible, in this case 800 gph, so that people know how much flow they can handle at the top end. If you were to go with a pump over the 800gph, the overflow wouldn't be able to handle the amount of flow and the water level in the display would be really high, if not overflow, unless you choked dowm the return pump or replaced with a smaller one.

Having said all that, there is no reason the pump gph has to match or even be close to the overflow gph. It surely will do just fine with anything lower than 800gph, even down to a couple hundred gph.

Can I use a ball valve to slow the return pump

 

[mfinn]

I’m thinking about adding a ball valve for the return, could it slow down the return pump a?

You can add a valve on the return line to slow down a return pump.
It will not harm the pump.

 

[theMeat]

With the overflow...
It’s rated for max flow it can handle. The less gph it has to handle, the quieter it will be. Most especially on a single drain overflow design

With return pump...
The old way of thinking was 10x display tank volume gph.
The newer way of thinking is 3-6x display tank volume.
Both ways of thinking work. Ime less works better, and also gives you some advantages like less heat and noise. With a 70 gal would shoot for 5x
Of coarse you have to figure in head pressure to that equation.

With that said would recommend you drill the tank for a ghost style overflow. Much safer than s hob, and quieter if you go with Herbie or bean animal style plumbing

If you’re not drilling the tank, or if you cannot because it’s tempered glass, do yourself a favor and get a hob, like cpr, that doesn’t rely on a u-tube. It has a way of keeping air out to maintain siphon, and will start itself when power comes back on