Return Pump Size

His Coral Highness · Mar 23, 2023

Probably a common question. Running a 75 gallon display with a 29 gallon sump under it. Deciding between 1 or 2 returns, but I think I'd like just 1 return pump to save space in the sump. The overflow is the Eshopps Medium rated at 800 gph. I figure this is the biggest determinant of what size pump I will need. What range should I be looking at for a return pump? I was thinking about 1700-2000 gph on a DC pump that I could dial down. It'd be about double the output of the overflow, which I think would be a safe bet given the head pressure coming back up to the tank. Is that the range I should be shooting for?

Rowboman · Mar 23, 2023

I’m definitely not a master of tank plumbing, but I’m pretty sure you’re taking a risk by sizing a return pump that rated for that much more than your overflow and could flood your tank. Typically return pumps are sized for turning over 5-10 times your tanks total volume per hour, so at most and 10 times your tanks volume is more than your returns rates for. So I’d stay under 800 gpa to be safe, unless someone knows something I don’t??

His Coral Highness · Mar 23, 2023

Rowboman said:
I’m definitely not a master of tank plumbing, but I’m pretty sure you’re taking a risk by sizing a return pump that rated for that much more than your overflow and could flood your tank. Typically return pumps are sized for turning over 5-10 times your tanks total volume per hour, so at most and 10 times your tanks volume is more than your returns rates for. So I’d stay under 800 gpa to be safe, unless someone knows something I don’t??

Yes I understand that risk, but with the DC sumps you can set them to 40%, 50%, 60% etc, so I could dial it back, but I wouldn't be able to exceed the upper limit

Crustaceon · Mar 23, 2023

Go with a 1000 gpa max dc pump and dial it down. You want to be around 200-300 gpa draining from the display which will probably be the lowest speed setting on a pump like that. I personally wouldn't put more than 25% of what that overflow is rated for.

Rowboman · Mar 23, 2023

His Coral Highness said:
Yes I understand that risk, but with the DC sumps you can set them to 40%, 50%, 60% etc, so I could dial it back, but I wouldn't be able to exceed the upper limit

Right, I kinda figured that would be the plan but unless you plan on increasing the total size of your system in the future I don’t see the reasoning for it, seeing as your buying a bigger pump than you need which is gonna cost more

mfinn · Mar 23, 2023

His Coral Highness said:
Probably a common question. Running a 75 gallon display with a 29 gallon sump under it. Deciding between 1 or 2 returns, but I think I'd like just 1 return pump to save space in the sump. The overflow is the Eshopps Medium rated at 800 gph. I figure this is the biggest determinant of what size pump I will need. What range should I be looking at for a return pump? I was thinking about 1700-2000 gph on a DC pump that I could dial down. It'd be about double the output of the overflow, which I think would be a safe bet given the head pressure coming back up to the tank. Is that the range I should be shooting for?

On a 75 gallon tank you really don't need much more than 400 to 450 gph. I would look for a dc ( if that's your goal) pump that gives you around 1200 gph. I use a Vectra M2 on my 66 gallon tank and run it about 33%.

His Coral Highness · Mar 23, 2023

Is there any reason to not have the overflow open at full capacity at 800 gph? Or to keep the overall flow to 400-450 gph? I am genuinely curious. I would've thought that it would only matter to match the output to the input.

mfinn · Mar 23, 2023

His Coral Highness said:
Is there any reason to not have the overflow open at full capacity at 800 gph? Or to keep the overall flow to 400-450 gph? I am genuinely curious. I would've thought that it would only matter to match the output to the input.

You want to have a little wiggle room. I wouldn't want to run the overflow at full capacity. A little bit of algae comes loose in the middle of the night and you could have issues.

stoney7713 · Mar 23, 2023

His Coral Highness said:
Is there any reason to not have the overflow open at full capacity at 800 gph? Or to keep the overall flow to 400-450 gph? I am genuinely curious. I would've thought that it would only matter to match the output to the input.

Snail, fish, sponges, algae, anything could get in it and block it partially, if it's already maxed out then you will have a flood. Leave plenty of wiggle room, it will also be quieter.

You don't need 10x through your sump. 3-5x is plenty. Most of your water circulation will come from powerheads.

PotatoPig · Mar 23, 2023

DC pump and dial it up/down as required.

Similar setup (75/20) After spending ages trying to get valves and flow rates from an AC pump working I swapped it for a DC one and absolutely no regrets.

As others have said - you don’t need that much turnover for the sump. A 600-800 gph drain system is plenty and a pump for ~200-400 gph range at the pump head you’re using should be fine.

Pistondog · Mar 23, 2023

His Coral Highness said:
Probably a common question. Running a 75 gallon display with a 29 gallon sump under it. Deciding between 1 or 2 returns, but I think I'd like just 1 return pump to save space in the sump. The overflow is the Eshopps Medium rated at 800 gph. I figure this is the biggest determinant of what size pump I will need. What range should I be looking at for a return pump? I was thinking about 1700-2000 gph on a DC pump that I could dial down. It'd be about double the output of the overflow, which I think would be a safe bet given the head pressure coming back up to the tank. Is that the range I should be shooting for?

I run one of these on my 75g. Dialed back to about 60%, silent
420 gallons per hour measured by apex flowmeter. 1 inch return hose with check valve.
Always have a backup.

Current USA eFlux DC Flow Pump with Flow Control 1050 GPH | Ultra Quiet, Submerisble or External Installation | Safe for Saltwater & Freshwater Systems https://a.co/d/fPxX7Ly

330Bob · Apr 17, 2023

His Coral Highness said:
Yes I understand that risk, but with the DC sumps you can set them to 40%, 50%, 60% etc, so I could dial it back, but I wouldn't be able to exceed the upper limit

I would never trust a DC pump set at 50 percent for a return pump without a ball valve limiter. They are computer based and subject to glitches. I had a DC pump lose power came back on FULL blast. Do you think the manufacture will cover that glitch?

What you do is put a ball valve or gate on the return line so it restricts your DC pump when its on Full blast setting. Once you find that go ahead and slow the pump to 50 percent. This way even if the DC pump loses its mind and goes full blast it won't flood your overflow and house.

mfinn · Apr 17, 2023

330Bob said:
I would never trust a DC pump set at 50 percent for a return pump without a ball valve limiter. They are computer based and subject to glitches. I had a DC pump lose power came back on FULL blast. Do you think the manufacture will cover that glitch?

What you do is put a ball valve or gate on the return line so it restricts your DC pump when its on Full blast setting. Once you find that go ahead and slow the pump to 50 percent. This way even if the DC pump loses its mind and goes full blast it won't flood your overflow and house.

So if you put a valve on a line and then restrict the flow, then you are forcing the pump to work harder than it needs too.
Doesn't make sense to me.
In the 15 years or so I've used dc pumps, I have never ever heard of one coming back on full power. I have 1-2 power outages at my house every year and it doesn't happen here.

C_AWOL · Apr 17, 2023

330Bob said:
I would never trust a DC pump set at 50 percent for a return pump without a ball valve limiter. They are computer based and subject to glitches. I had a DC pump lose power came back on FULL blast. Do you think the manufacture will cover that glitch?

What you do is put a ball valve or gate on the return line so it restricts your DC pump when its on Full blast setting. Once you find that go ahead and slow the pump to 50 percent. This way even if the DC pump loses its mind and goes full blast it won't flood your overflow and house.

Not saying that will never happen but I haven't personally experienced that with any dc pumps i've used.

Either way, using a pump thats sized accordingly to your overflows capability will simply mean that in the event where something like that could happen, then the overflow can handle it with 0 issues rather than relying on a ball valve/gate valve to work a dc pump a lot harder.

PotatoPig · Apr 17, 2023

330Bob said:
I would never trust a DC pump set at 50 percent for a return pump without a ball valve limiter. They are computer based and subject to glitches. I had a DC pump lose power came back on FULL blast. Do you think the manufacture will cover that glitch?

What you do is put a ball valve or gate on the return line so it restricts your DC pump when its on Full blast setting. Once you find that go ahead and slow the pump to 50 percent. This way even if the DC pump loses its mind and goes full blast it won't flood your overflow and house.

Wouldn’t you have the pump in a return chamber instead? Then worst case is it lowers the water level in the return chamber enough that it starts sucking in air and working as an unwanted aerator.

330Bob · Apr 18, 2023

mfinn said:
So if you put a valve on a line and then restrict the flow, then you are forcing the pump to work harder than it needs too.
Doesn't make sense to me.
In the 15 years or so I've used dc pumps, I have never ever heard of one coming back on full power. I have 1-2 power outages at my house every year and it doesn't happen here.

I've used both for 20 years. And DC pumps failure point is the electronics they don't hold up as well as old Iwaki or panworlds. They have more features and use less juice. Not saying you can't have a DC run well for years but there will be more issue if you look at 100,000 of them vs AC pumps. Simple vs complex. I have one DC that has been good three years but did lock up a few times year one.
You can valve back a AC pump and they will use less electricity like 80 watts less.

Electronics fail they are a weak link just the way it is. Not saying every power outrage on every pump does it just saying they are less reliable. If the DC pump at 100 percent floods your tank that is a concern. My AC will so I valve it back a little or if using a reactor I can bleed off some of its excess. I trust mechanical valves over electronics for flow every day and twice on Sundays.

mfinn · Apr 18, 2023

330Bob said:
I've used both for 20 years. And DC pumps failure point is the electronics they don't hold up as well as old Iwaki or panworlds. They have more features and use less juice. Not saying you can't have a DC run well for years but there will be more issue if you look at 100,000 of them vs AC pumps. Simple vs complex. I have one DC that has been good three years but did lock up a few times year one.
You can valve back a AC pump and they will use less electricity like 80 watts less.

Electronics fail they are a weak link just the way it is. Not saying every power outrage on every pump does it just saying they are less reliable. If the DC pump at 100 percent floods your tank that is a concern. My AC will so I valve it back a little or if using a reactor I can bleed off some of its excess. I trust mechanical valves over electronics for flow every day and twice on Sundays.

I'm not saying dc pumps are more reliable than ac pumps. Used them for near 35 years. Done it in most every case.
And putting a valve on a ac pump to cut back the flow is pretty common.
What I am saying is your suggestion that putting a valve on a dc pump to throttle it back just in case the controller fails and sticks on 100% is not making sense to me at all.
I have never heard of a dc pump going haywire and getting stuck on 100%. Throttling it down is just making the pump work harder, and then in theory having a shorter life.
Just not needed.

spsick · Apr 18, 2023

On my 75 I’m turning over 200-300gph and very happy with it. Using a RD3 Mini Speedy throttled down. Before that a Tunze 1073.040 that was reliable and also perfect sized. Bought that when they came out 10+ years ago and it still works when I need it. Best $150 I’ve ever spent in this hobby.