Return pump speed and sump water level question

[glb]

I have a Jebao DCT 6000 return pump and a 700 series glass-holes overflow kit that I'm test running on a new 40g breeder setup. I have 'pump on' and 'pump off' water lines marked on the sump. Here's my question. The first time I turned up the pump speed, the water level went down in the sump and stayed lower, meaning more water is staying in the display tank. My overflow has 1 1/2" PVC and the return is 3/4" as recommended by glass-holes. Is this a problem? Does this mean my pump needs to stay at a lower speed? It's hard to believe that 1 1/2" pipes can't handle more water. I can tell that the 1 1/2 PVC isn't full when the water drains. I'm new to all this so any help is appreciated!

 

[cmcoker]

The amount of water that can get into the overflow, over/through the weir, will limit your the water leaving the tank though, if that makes since..

As far as pump speed, what is happening with the water level in the tank? Still some room? About to overflow?

You don't want the water level too high going into the overflow cause you will get surface film accumulating

 

[saltyfilmfolks]

whats the return rate your going for? did you do the math? either your over on the GPH of the pump under on the return.
Im thinking over on the pump. My 55g w 25g sump has a 3300 and is at 10x.
and 10x it too fast really. I just bought a 4000 dc to slow it to a 5 to 7 x return.

 

[glb]

The amount of water that can get into the overflow, over/through the weir, will limit your the water leaving the tank though, if that makes since..

As far as pump speed, what is happening with the water level in the tank? Still some room? About to overflow?

You don't want the water level too high going into the overflow cause you will get surface film accumulating

The water level in the display tank is just a little higher, so it's not going to overflow. And I can always turn the pump down if I need to.

 

[glb]

whats the return rate your going for? did you do the math? either your over on the GPH of the pump under on the return.
Im thinking over on the pump. My 55g w 25g sump has a 3300 and is at 10x.
and 10x it too fast really. I just bought a 4000 dc to slow it to a 5 to 7 x return.

Isn't it the tank volume x 10? This overflow is rated to 700gph. My tank is 40g so my best guess is 400gph. I'll have to look up the pump settings. Like I said above, I can turn it down. The factory setting is a 4 of 10 so I've got plenty of wiggle room.

 

[saltyfilmfolks]

tank vol + sump vol x return rate = gph needed
my tank now
55+20 = 75g total vol x 10x return rate = 750 gph pump my 10x is too fast
75g total x 7x = 525gph that i want

yours
40+ 20= 60gal total vol x 7x ?return rate = 420ghp pump for a 7x return rate
this does not calculate head loss.

your 6000 Lph pump is 1500 ghp

 

[glb]

tank vol + sump vol x return rate = gph needed
my tank now
55+20 = 75g total vol x 10x return rate = 750 gph pump my 10x is too fast
75g total x 7x = 525gph that i want

yours
40+ 20= 60gal total vol x 7x ?return rate = 420ghp pump for a 7x return rate
this does not calculate head loss.

your 6000 Lph pump is 1500 ghp

Thanks. Since the pump has 10 adjustable settings, I should be good. Did you pick 7x because my tank is smaller? How do I calculate head loss? I know the height of rhe pipes and number of fittings matter.

 

[AZDesertRat]

Headloss is the vertical distance from the sump water level to the display level measured in feet of head. Then you would add an additional foot or two for all the fittings and friction losses in the piping. 5-6 feet of headloss is pretty normal. Look at your pump curve and see where 5 or 6 feet of head puts your flow.

Depending on the volume of water in your sump you may want to keep the return flow at around 3-5x the display volume so you don't have microbubble issues in the display. It is cheaper energy wise to make up the bulk of your turnover in the display with wavemakers/powerheads which only draw a couple watts each and give you a more random flow than a return. The lower return flow also makes your in sump protein skimmer more efficient as it has more time to process organics with a lower velocity through the sump chambers.

 

[saltyfilmfolks]

Did you pick 7x because my tank is smaller? How do I calculate head loss?

7x is just an example. Im going 7x as I keep a lot of filter feeders. there is no real consensus it seems. 3x to 10x appears to be the general range.
on many websites and sometimes on the pump box itself there are usually head loss details. most home systems I see are fairly basic though.
AZ has it right.

 

[fab]

How do I calculate head loss? I know the height of rhe pipes and number of fittings matter.

Google it! There are tons of "Betty Crocker" cookbooks out there on this exact subject. It is really easy to learn.

A very basic factor is that the relationship between flow rate and pipe diameter is that flow rate goes up with the square of the pipe diameter. So if you double the pipe diameter you can quadruple the flow rate you can put through it.

Head is pressure working against the pressure put out by the pump, so head pressure subtracts from pump pressure thus reducing the actual flow rate a pump can produce. Head pressure is the combination of all of the resistive pressures the pump must overcome to produce a given volumetric flow rate through you pipe system.

The major resistive pressures a pump must overcome are caused by:

1. Static pressure. Note: Weight/Area = Pressure. The weight if water that must be pushed upwards by the pump. This pressure equals the water weight/cross-sectional area of the pipe.
2. Pipe surfaces produce frictional forces that act against a pump that is trying to push water through a pipe. These frictional forces accrue over the total surface area of the pipe that the water touches. That is called the pipe's wetted area. It is determined by the diameter and the length of the pipe. Specifically the wetted area equals the pipe circumference x pipe length. The total frictional force equals a friction factor x the total wetted area. The friction factor is determined by the surface roughness of the pipe material you use.
3. Dynamic pressure. Caused by flow form factors that have to do with changes in flow channel direction, size and shape due to various pipe fittings. An equation called Bernoulli's flow equation governs these resistive pressures. This is where the math departs from the trivial arithmetic above.

Fortunately, the "Betty Crocker" approaches provide sets of tables so you can look up the pressures produced by water weight and velocity, vertial height, pipe material and diameter, and Bernoulli's stuff for fittings instead of having to calculate any of it.

You'll find these tables when you Google for "head losses for flow in pipes."

Use the simplest tables you find. The not-so-simple ones are for complex piping systems. Aquarium piping systems are ALL simple, no matter how complicated we try to make them, even mine.

BTW,
1. @AZDesertRat and @saltyfilmfolks are spot on for roughly approximating your numbers.
AND
2. Bernoulli really covered #1 and #3.
3. A bunch of guys did the heavy lifting for #2, but Darcy, Weisbach and Moody are the big names.
4. No that is not a law firm.

Good luck, fab

 

[glb]

Thanks everyone. I googled and have found approximations for my fittings in gph. Do I subtract this loss of head for the return plumbing only or for the overflow as well?

 

[glb]

I just found this cool excel spreadsheet that does the work for you. I'm going to check it out when I get home.
http://www.advancedaquarist.com/2003/1/aafeature2_files/waterpipe-v1.xls

 

[fab]

Do I subtract this loss of head for the return plumbing only or for the overflow as well?

Only the return plumbing has a pump in it. Head pressure acts against the return pump. So only do the calculations for the return plumbing.

The overflow system is a different beast for calculating flow rates. It involves
1. water flowing over a weir
2. Water flowing through a possibly full siphon
3. Water flowing through a partially full water channel of closed pipe and possibly not all vertically
4. Water draining by gravity through a closed pipe.
5. Minimal interfereces to flow due to fitting

#1 and #3 can be a complicated mess mathematically. The detailed physics are not trivial. But after all is said and done you can bypass all of that by making a few simple measurements. Screw the physics and the math. You can do the measurement approach on both parts, overflow and return. Do them separately and independently. Shut off the overflow and see how long it takes to raise the display tank level by a inch or so. Then with the tank still "overkill" turn off the return first then open the overflow. Time how long it takes to drain an inch or so from the display tank. Calculate the actual flow rates from these mrsurements. Record your measurements. Do this about 10 times and average the results. Of you change your pump setting (pump speed) then repeat the 10 reps to calculate the new return flow rate and corresponding overflow rate.

As you continue to increase the return pump flow rate you may see the overflow rate cease to increase. That is when you have reached the maximum flow rate capacity of your overflow system and it plumbing. You should run your return pump at flow rates that are below the max flow rate capacity of your overflow system.

Remember that overflow pipes grow stuff on their insides, snails and other critters get sucked into them. These cause flow restrictions that reduce max flow rate capacity in our overflows. That is why you need to monitor display and sump tank water levels. Clogged overflows will cause sump level to drop drastically and all that water ends up in the display tank or on the floor. The opposite occurs when the return lines get clogged, plus pumps may overheat or even run dry.


Tinkering and measuring will give you reliable results if you do it carefully and you will get a good personal feel for your system's actual behavior.

BTW,
Bernoulli rides again plus another horde of old-timers along with him on these topics.

 

[glb]

I just found this handy chart that shows power levels for each speed setting. I'm using to calculate gph, more or less

These are the numbers I came up with:

Once I take all the head loss into account, I can definitely get this pump to work with my setup.

 

[glb]

I just found this cool excel spreadsheet that does the work for you. I'm going to check it out when I get home.
http://www.advancedaquarist.com/2003/1/aafeature2_files/waterpipe-v1.xls

Never mind on this. It's old so it doesn't have the current pumps

 

[roosterchef]

I couldn't find a good head loss calculator that took everything into account, including vertical feet. But, there are several online that are good for everything else, including type of pipe, bends, fittings, etc. Use one of those, then add the vertical feet of rise in your tank from pump to top of your return line.

You can't just rely on the power factor for your pump to calculate your flow, however. Two different pumps rated exactly the same can have different flow rates on their head loss curve, so you need to use the curve for your pump and let it tell you the gph based on the head loss you calculate in step one. *Then* I would apply the power factor from your chart to that number, because the head loss curve from the pump manufacturer will probably be at 100% power.

 

[glb]

Ok I think I have it figured out. I found a calculator that takes pipe size length of pvc, fittings etc into account. It showed a 6.87 foot loss of head pressure. After doing the calculations, my pump would push 713gph at full speed. At speeds 3,4 and 5, I get 399, 442, and 485gph respectively. So it seems that the factory setting of 4 is the best setting after all. Lol. I'm glad the sweet spot isn't at either extreme of the pump's limitations. Thanks everyone for your help!!!

 

[saltyfilmfolks]

Ok I think I have it figured out. I found a calculator that takes pipe size length of pvc, fittings etc into account. It showed a 6.87 foot loss of head pressure. After doing the calculations, my pump would push 713gph at full speed. At speeds 3,4 and 5, I get 399, 442, and 485gph respectively. So it seems that the factory setting of 4 is the best setting after all. Lol. I'm glad the sweet spot isn't at either extreme of the pump's limitations. Thanks everyone for your help!!!

sweet. gotta link?

 

[glb]

sweet. gotta link?

Here it is. It didn't have my particular return pump so I picked one with the same gph. Good luck!
http://www.reefcentral.com/index.php/head-loss-calculator

 

[glb]

Only the return plumbing has a pump in it. Head pressure acts against the return pump. So only do the calculations for the return plumbing.

The overflow system is a different beast for calculating flow rates. It involves
1. water flowing over a weir
2. Water flowing through a possibly full siphon
3. Water flowing through a partially full water channel of closed pipe and possibly not all vertically
4. Water draining by gravity through a closed pipe.
5. Minimal interfereces to flow due to fitting

#1 and #3 can be a complicated mess mathematically. The detailed physics are not trivial. But after all is said and done you can bypass all of that by making a few simple measurements. Screw the physics and the math. You can do the measurement approach on both parts, overflow and return. Do them separately and independently. Shut off the overflow and see how long it takes to raise the display tank level by a inch or so. Then with the tank still "overkill" turn off the return first then open the overflow. Time how long it takes to drain an inch or so from the display tank. Calculate the actual flow rates from these mrsurements. Record your measurements. Do this about 10 times and average the results. Of you change your pump setting (pump speed) then repeat the 10 reps to calculate the new return flow rate and corresponding overflow rate.

As you continue to increase the return pump flow rate you may see the overflow rate cease to increase. That is when you have reached the maximum flow rate capacity of your overflow system and it plumbing. You should run your return pump at flow rates that are below the max flow rate capacity of your overflow system.

Remember that overflow pipes grow stuff on their insides, snails and other critters get sucked into them. These cause flow restrictions that reduce max flow rate capacity in our overflows. That is why you need to monitor display and sump tank water levels. Clogged overflows will cause sump level to drop drastically and all that water ends up in the display tank or on the floor. The opposite occurs when the return lines get clogged, plus pumps may overheat or even run dry.


Tinkering and measuring will give you reliable results if you do it carefully and you will get a good personal feel for your system's actual behavior.

BTW,
Bernoulli rides again plus another horde of old-timers along with him on these topics.

Thanks! I have a lid on my overflow box so hopefully that will keep most critters out. And I have unions all over the system so I can dissemble and clean as needed.[/QUOTE]