• For a Limited Time the R2R Partner Membership is NOW OPEN! Get some cool swag and chances to win part of over $20,000 in prizes! Click here for more details

Why is there a common trend to grossly oversize return pumps on a new build.

DCR

Active Member
View Badges
Joined
Jan 3, 2018
Messages
238
Reaction score
160
I have a Jebao DCP 18000 rated for 4,755 GPH and I get 4,755 GPH of flow. So, all you hydro wizards.. how am I using this pump to get the rating for zero head pressure?.....
I am curious how you know you are getting 4755 gph? That is a massive flow rate which would probably require multiple 1.5 or 2" lines to achieve. Certainly cannot bucket test it since it would fill a 5 gallon bucket in about 4 seconds . Either the measured flow is not accurate or the manufacturers data is not accurate.
 
https://www.omegasea.net/

pdxmonkeyboy

Sticks!! Give me the sticks!
View Badges
Joined
Mar 7, 2017
Messages
2,494
Reaction score
4,095
Location
Hockinson, WA
Not sure why you think the manufacturers data is not accurate. It is rated for 18,000 lph.
It filled a 20 gallon rubbermaid faster than I could say " OH MY GOD this thing is nuts..." It was a hair over 16 seconds and that was with 3' of head on it.

It runs at 36v and has a 1.5 inlet and outlet. My hammerhead pushes more than that with a single 1.5" line. I think my hammerhead would still push more water, but in regards to assumption that I am not getting that much flow. ... ummm. Ya huh.
 
OP
Palegic

Palegic

Active Member
View Badges
Joined
Jul 20, 2020
Messages
124
Reaction score
114
Location
Long Island
I am curious how you know you are getting 4755 gph? That is a massive flow rate which would probably require multiple 1.5 or 2" lines to achieve. Certainly cannot bucket test it since it would fill a 5 gallon bucket in about 4 seconds . Either the measured flow is not accurate or the manufacturers data is not accurate.
Well they make reletively inexpensive devices to measure flow. You could also simply measure the time it takes to empty a pre measured amount of water however it will be innacurate due to ramp up time. Or um fill a larger say 32g brute..
 

JasonK84

I want more!!!
View Badges
Joined
Sep 14, 2018
Messages
2,747
Reaction score
7,787
Location
Amarillo
Thats the response I was looking for! lol as that would be the smartest reason to oversize your equipment. Otherwise I feel like its a kind of a waste of power, generates more heat, and noise...especially if not DC.
I just got a new truck 3 weeks ago and got the 6.2L engine! Why? Because I can! Wouldn’t the 5.3L have been fine? Sure. The 6cyl would have been fine even.

My 120 gallon tank has a return pump that says it puts out 3170gph max. Why? Because I can. I keep it at 50%. I also have a spare. No sense pushing things to their max operating range.
 

pdxmonkeyboy

Sticks!! Give me the sticks!
View Badges
Joined
Mar 7, 2017
Messages
2,494
Reaction score
4,095
Location
Hockinson, WA
Its has nothing to do with measurements, it is simply physics, just thought it would be interesting to see who could figure a configuration where you loose absolutley no flow do to head preasure.
I guess we know one person who can not.
 

naterealbig

Valuable Member
View Badges
Joined
Sep 1, 2018
Messages
1,317
Reaction score
1,857
Location
Tampa
Well you loose redundancy by running equipment off a manifold from the return pump and it makes it more difficult to measure the flow through your sump.

I half heartedly agree about having more power than needed. Running a pump capable of 25-50x just seems like an excessive amount and possibly shows that some people may not understand how little sump turnover they need for success.
You may gain redundancy, but you lose reliability depending on the pumps you use. The trend towards unproven and unreliable DC return pumps (each with double the points of failure of an AC pump) unfortunately requires the use of several pumps due to the low MTF (of the power supply or the controller).

The use of a single, large, quality AC pump (Eheim, Danner, Fluval) negates the need for DC pump redundancy. Run two of these in parallel, and you have a bulletproof system.

You cite a large return flow as a cause of low nutrients. This isn't true in all cases (No filter sock), and many accomplished refers operate with ULNS systems, so in some cases it is desirable.

I use two large AC return pumps on my system and I have no plan to upgrade. Lots of in-tank circulation is great, but without a healthy return flow the detritus doesn't end up in your overflow..... It just circulates in the tank and settles in the rock. I like to get the junk over the overflow and into my filtration so it can be processed. The high flow is particularly handy when I'm cleaning my display.

Also I clean my sump using my returns. I open up the gate valve on the returns, and bypass my display directly to mechanical filtration. I can clean my sump to like-new in about 8 minutes. This would take hours with a small return pump.

Finally, depending on the complexity of the plumbing system you will need a pump several times the flow of your desired output. In most of my systems head losses account for approximately 50-60% loss of flow. Right off the bat, plan on doubling the size of your return pump once you have calculated your required turnover.
 

All Delight

2500 Club Member
View Badges
Joined
Aug 14, 2008
Messages
2,724
Reaction score
472
Location
Long Beach, Cali
Regarding high turnover stripping the tank of nutrients, lower turnover actually makes your skimmer more efficient since there is longer contact time to remove wastes.

With DC pumps I usually go around 15x turnover to compensate for head loss plus I clean my return pumps maybe every 2 years so performance does decrease and I don’t run then 100%. I like to tune it down.
 

92Miata

Well-Known Member
View Badges
Joined
Feb 26, 2020
Messages
533
Reaction score
670
Location
Richmond, VA
Here’s a prime example of a popular 1400 gph DC controllable pump only actually pumping 250 gph at full throttle as measured by a flow meter. Head pressure loss due to height, plumbing restrictions and elbows do a lot to reduce flow, more than many are actually accounting for IMO.

That's an example of someone running completely inadequate plumbing.

People need to stop trying to push 1000gph through 3/4" plumbing and being surprised that they get a lot of head loss.

Yes, DC pumps tend to be designed for flow rather than head - but the major culprit in the vast majority of situations is plumbing.
 

Water Dog

2500 Club Member
View Badges
Joined
Mar 28, 2016
Messages
3,611
Reaction score
4,102
Location
Fairfield, CT
That's an example of someone running completely inadequate plumbing.

People need to stop trying to push 1000gph through 3/4" plumbing and being surprised that they get a lot of head loss.

Yes, DC pumps tend to be designed for flow rather than head - but the major culprit in the vast majority of situations is plumbing.
When the pump comes stock with a 3/4” outlet slip fitting, it’s the end users fault... got it. :rolleyes:

 

92Miata

Well-Known Member
View Badges
Joined
Feb 26, 2020
Messages
533
Reaction score
670
Location
Richmond, VA
When the pump comes stock with a 3/4” outlet slip fitting, it’s the end users fault... got it. :rolleyes:
Pump orifice size and plumbing size don't need to be the same. Plumbing size should almost always be upsized.

This has nothing to do with DC pumps - any pump trying to move 1000+ gph through 3/4" PVC for any sort of distance is going to see heavy friction losses.
 

DCR

Active Member
View Badges
Joined
Jan 3, 2018
Messages
238
Reaction score
160
When the pump comes stock with a 3/4” outlet slip fitting, it’s the end users fault... got it. :rolleyes:

Centrifugal pumps are designed with restricted outlet nozzle sizes to improve their internal efficiency. It is incorrect to assume that you should just match the discharge port size. The discharge line should almost always be increased immediately after the discharge nozzle at least one pipe size and often two pipe sizes. Having sized piping systems professionally for almost 40 years, my general recommendation would be 3/4" up to 300 gph, 1" up to 600 gph, 1-1/4" up to 1200 gph, 1-1/2" up to 1800 gph and 2" up to 3600 gph. This will keep your frictional losses to a modest level. You can push these limits, but your are going to be running increasingly more power on your pump. The cost of larger diameter piping is much less than the additional power consumption. It makes no sense to buy these expensive DC pumps to save power and then use undersized piping that causes them to run at a higher speed and negate the benefit of the variable speed pump. Most people just live with lower flow rates than what they expected.
 

Water Dog

2500 Club Member
View Badges
Joined
Mar 28, 2016
Messages
3,611
Reaction score
4,102
Location
Fairfield, CT
This has nothing to do with DC pumps - any pump trying to move 1000+ gph through 3/4" PVC for any sort of distance is going to see heavy friction losses.
But it has everything to do with the whole point of this thread as to why people are “grossly” oversizing their pumps. The S1 example is a perfect case in point. The 1400 gph rated pump’s stock slip fitting is 3/4”. His RedSea Reefer‘s stock return plumbing is around 3/4” (or close, it’s actually metric). Perhaps he should have “grossly” oversized his pump as well to accommodate his stock RedSea Reefer return plumbing.
 
Last edited:

92Miata

Well-Known Member
View Badges
Joined
Feb 26, 2020
Messages
533
Reaction score
670
Location
Richmond, VA
But it has everything to do with the whole point of this thread as to why people are “grossly” oversizing their pumps. The S1 example is a perfect case in point. The 1400 gph rated pump’s stock slip fitting is 3/4”. His RedSea Reefer‘s return plumbing is around 3/4” (or close, it’s actually metric). Perhaps he should have “grossly” oversized his pump as well to accommodate his stock RedSea Reefer return plumbing.
Or he could run a smaller pump and get similar results.


Head losses beyond height are proportional to velocity (squared I believe). Using a significantly higher flow pump just gets you significantly more head loss and marginally more flow.

He'd get more performance running a 1.25" line between the pump and the return nozzle than he'd get doubling the size of the pump.
 

Water Dog

2500 Club Member
View Badges
Joined
Mar 28, 2016
Messages
3,611
Reaction score
4,102
Location
Fairfield, CT
Or he could run a smaller pump and get similar results.


Head losses beyond height are proportional to velocity (squared I believe). Using a significantly higher flow pump just gets you significantly more head loss and marginally more flow.

He'd get more performance running a 1.25" line between the pump and the return nozzle than he'd get doubling the size of the pump.
I totally understand your point about plumbing size and efficiency, I really do. But again, Red Sea Reefer tanks, from the smallest Reefer 170 at 35 gallons to the largest 750xxl at 160 gallons come standard with their own flex tubing which attaches to their hard return plumbing. Is it the hobbyist‘s fault for not upsizing the plumbing on their “plug and play” set up? The same applies to the slip or barb fitting that come stock with pumps. Unless you have plumbing expertise, are hobbyists at fault for not knowing that they have to upsize their plumbing after the included pump fittings to come closer to the advertised flow specs? Without knowing these intricacies of plumbing efficiency, as the OP put it, there has been a trend for hobbyists to “grossly“ oversize their pumps... in order to achieve the flow rates they’re looking for.
 
Last edited:

BillFish Coral Lover

Community Member
View Badges
Joined
Mar 21, 2020
Messages
32
Reaction score
17
So, I'm guessing people are confusing high flow in the tank for sps with turnover. Anyway, I've been planning a manifold and everything I read here says to double the normal return (usually stated as 10x, so now 20) due to head pressure and loss of flow from turns, etc.
What I don't understand are your blanket statements of fact that:

(1) such a manifold takes away redundancy - what redundancy? The water enters the sump and goes through whatever filtration you have. You're not really getting redundancy unless you're recirculating through the sump. Otherwise, if you use a manifold or still goes through each filtration item once. In fact, if you use a manifold it guarantees that the water goes through. Without it, some water will always bypass some of the filtration items in the sump, so not only is there no redundancy (without recirculation within the sump), but you actually can assign specific parts of the manifold to filter items you want to guarantee you get the water through.

(2) faster flow "strips the water of nutrients." Which nutrients? How exactly? If you back it up by saying, for instance, running the entire system's water through a phophate reactor in sump 10x per hour overstrips phisphate needed for the health and color of corals (some more than others, I'm assuming), that would make sense. However, there are people who want to do just that.

Personally I'm running return at about 8-10 times per hour and bypassing the refugium with a little more than half that flow to keep it closer to 4-5 per hour.
 

How often do you have some type of algae issue?

  • Constantly Something

    Votes: 34 40.5%
  • Every Month

    Votes: 1 1.2%
  • Every Few Months

    Votes: 9 10.7%
  • A Few Times A Year

    Votes: 11 13.1%
  • Once A Year Or So

    Votes: 9 10.7%
  • Every Few years

    Votes: 3 3.6%
  • Never.....(are you lying?)

    Votes: 12 14.3%
  • Other (please explain)

    Votes: 5 6.0%

Online statistics

Members online
2,071
Guests online
3,986
Total visitors
6,057
Top