Restricting water flow to/from your sump

[Toxic Slurpee]

So this is my first new tank with a sump, what's the trick to getting the water to stay at the level you want?

I have gate valves on the drain & return lines (both are 1" PVC) I can adjust. Is it best practice to keep the drain valve wide open then make small adjustments on the return gate valve?

I have a plenty large enough sump so I am not worrying about it overflowing...just having a difficult time getting the water depth to stop at the right spot in the middle.

[Allmost]

water level in sump ? it should be controlled by a set of baffles, so your skimmer section has stable water level, and your return section goes down, as the water evaporates.


leave the gate valve at drain fully open.

and adjust the return valve, to what the drain can handle. if water level in tank rising, then return is too strong.

[rwb500]

the water level is NOT set by adjusting flow rates. never restrict your drain line, unless you are trying to minimize noise and you are absolutely sure there is still plenty of drain capacity. this would be something to try, if necessary, when you have a better understanding of your system.

[MaLi]

IMHO it is a bad practice to install a valve on the drain line. It is a certain recipe for disasters. If you want to decrease the flow your only option is to regulate the inlet of the return pump. Remember, I said the inlet. If you regulate the outlet you will strain your pump and reduce its life span. You will also have to figure out a way to control the amount of air the overflow ingests. The lower the flow more air is required (i.e. larger hole on a durso).

hope it helps,
MaLi

[uncleof6]

Restricting the pump intake, is the number one FAQ in most pump information. Doing so, will cause the pump to cavitate, and can/will cause damage to the pump--such as destroying the impeller, up to bending the pump shaft. Invariably the instructions will say NEVER restrict the pump intake, or reduce the size of the pump intake to smaller than the pump outlet. A valve adjustment will do both. If you noticed just about every pump has an intake larger than the outlet. You can however, increase the pump outlet size--to reduce friction loss.

The only place flow rate is controlled through a system is by using a valve on the pump OUTLET. Different pumps, respond differently, to this added friction loss/head loss. Your mileage will vary depending on the pump.

Best practice, though it does not lend itself to rules of thumb, is to choose a pump that will provide the desired flow rate in the system you design--with just a minor adjustment of the valve, rather than rushing out and buying a pump cause so and so says it is a good pump, and then throttling the pump because it is too big, or redoing everything because the pump is too small.

[MaLi]

Restricting the pump intake, is the number one FAQ in most pump information. Doing so, will cause the pump to cavitate, and can/will cause damage to the pump--such as destroying the impeller, up to bending the pump shaft. Invariably the instructions will say NEVER restrict the pump intake, or reduce the size of the pump intake to smaller than the pump outlet. A valve adjustment will do both. If you noticed just about every pump has an intake larger than the outlet. You can however, increase the pump outlet size--to reduce friction loss.

The only place flow rate is controlled through a system is by using a valve on the pump OUTLET. Different pumps, respond differently, to this added friction loss/head loss. Your mileage will vary depending on the pump.

Best practice, though it does not lend itself to rules of thumb, is to choose a pump that will provide the desired flow rate in the system you design--with just a minor adjustment of the valve, rather than rushing out and buying a pump cause so and so says it is a good pump, and then throttling the pump because it is too big, or redoing everything because the pump is too small.

Uncle,

what you said is right, if you restrict the inlet flow to the point of cavitating the pump, you may be better served by a smaller pump. Restricting the outlet is a certain way of fatiguing the impeller. Look at all the adjustable flow pumps in the market and give me an example of on that comes with an adjustment on outlet.

A better way of regulating the sump flow is tee-ing up the outlet with a ball valve and returning the line back in the sump. Adjusting the return will increase/decrease the sump flow.

hope it helps,
MaLi

[fishgate]

I had this same issue - how to control the sump level. I found that the more water (level) that was in the tank, the more water flowed out of the overflow into the sump. As the tank level rises, the flow increases since more water enters the overflow section until you reach equilibrium. Mine has naturally found the exact right level that it was designed for (Eshoppes sump).

[BeanAnimal]

IMHO it is a bad practice to install a valve on the drain line. It is a certain recipe for disasters. If you want to decrease the flow your only option is to regulate the inlet of the return pump. Remember, I said the inlet. If you regulate the outlet you will strain your pump and reduce its life span. You will also have to figure out a way to control the amount of air the overflow ingests. The lower the flow more air is required (i.e. larger hole on a durso).

hope it helps,
MaLi

In fact you have it somewhat backward :)

Restricting the output of a centrifugal pump REDUCES the amount of work it does and taht in turn REDUCES the power consumption and also the "strain" on the pump. The PROPER way to restrict flow is to valve back the output, not restrict the input. This is basic physics at work and centrifugal pumps 101 :)

Restricting the outlet is a certain way of fatiguing the impeller. Look at all the adjustable flow pumps in the market and give me an example of on that comes with an adjustment on outlet.

A better way of regulating the sump flow is tee-ing up the outlet with a ball valve and returning the line back in the sump. Adjusting the return will increase/decrease the sump flow.
Valving back the pump's output does not fatigue the impeller or stress the compnents in any way unless the pump is valved back so far that it can not shed heat created by the friction of the circulating water. That is, most centrifugal pumps are okay valved back to nearly a dead head (full shut off) state. A "water cooled" wet end (one where the heat of the motor is wicked away through the wet end should not be valved back more than about 75% (tough rule of thumb). Again, valving back a pump's output reduces its power consumption...

... So if valving back the output reduces power consumption what does using a "recirculating Tee" on the output do? Well of course it increases power consumption by allowing the pump to do more work by reducing the head against the pump. Rrunning water in circles is a waste of money :) Valve the output back or purchase the next smaller size pump :)

Look at all the adjustable flow pumps in the market and give me an example of on that comes with an adjustment on outlet. They don't come with inlet valves for adjustment either, save a few small powerheads. Using the "they don't come with it, so it must not be a good idea" logic is falacy. :) A pump is built and a flow profile (called a pump curve) is charted. The end user is supposed to choose the pump based on the desired flow in relation to the head of the system it is being attached to by choosing a pump that operates at BEP (best efficiency point) on the pump curve on the system in question. Then no valving back would be needed. In reality, most pumps are slightly oversized and then regulated (at the putput) back to BEP, as if they were undersized there would be no way to "push them forward" to BEP. Hope that makes sense.



Also, with regard to the durso: If the "air hole" in the durso is regulating the flow, then basic physics says that the system will be unstable and require constant tuning. A "durso" works best when the standpipe runs in open channel flow, and is not regulated by "air". However, that discussion is best left for its own thread :)

[MaLi]

Bean,

what if you take a look at a Tunze 1073 series pump ? This is not a power head by all means. As far as flow through Durso and the amount of air needed, please take a look here: http://www.dursostandpipes.com/make-your-own-diy?start=2

regards,
MaLi

[CliftonArbogast]

+1 on Bean, he has the correct view of pump dynamics and principles. I work in a chemical plant (engineer) and make a living using pumps correctly. . . . most of the time

[BeanAnimal]

Bean,

what if you take a look at a Tunze 1073 series pump ? This is not a power head by all means. As far as flow through Durso and the amount of air needed, please take a look here: http://www.dursostandpipes.com/make-your-own-diy?start=2

regards,
MaLi


Sure it is a "powerhead" :) at 6 feet of head, it has 0 output. At 3 feet of head it has 300GPH of output. That is, used as a "pump" it will likely never see more than 200-300GPH at the output. Restricting the "input" certainly limits the pump's ability to draw in water, but due to the design and low flow, cavitation is not likely. The "valve" on the inlet is part of the volute right at the impeller. Notice that the newer 1073.05 has a "smart" controller that shuts the pump off if the intake is blocked, and likewise adjusts the motor speed to control flow, no need to valve back the output.

Rest assured, valving back the output of a centrifugal pump is the PROPER way to reduce flow. The intake should NEVER be valved back to control flow.

With regard, to the Durso standpipe design (and with all due Respect to Richard Durso), I understand the physics of the design and how it works. In Richard's own words he explains he somewhat doesn't understand the physics, but just stumbled upon something that works for him.

The key point is that an "air assisted" standpipe (Durso, Sotckman, Hoffer, whatever) is only stable given the alignment of several environmental variables. If the "air" is used as the governor, then the system is at partial siphon and stability of the system is DEPENDENT on the regulation of the air. This style of standpipe is actually rather limited to quiet and stable operation over a small range of flow rates. Outside of that range (dictated by many local variables) the system will be either unstable, noisy and/or inject huge amounts of air into the discharge stream. This is far from ideal and again, a subject better left to a dedicated thread. My overflow project pages (and thread) have quite a bit of discussion on the subject, as does the "herbie" overflow thread.

:)

[firebirdude]

To get back to what the OP is asking, Allmost nailed it. The critical areas of your sump that need a constant water level (skimmer) should be set with a baffle. Only the final return chamber's water level will fluctuate with evaporation. In this area is where you'd want to install your float switches for your ATO.

If you just want to limit flow through your sump, throttle back on the return pumps output back to the display. This is reduce the amount of water into the display, thereby, reducing the amount of water through your overflow and back into the sump. As already said, NEVER limit the flow through the overflow/sump inlet. Your return pump would continue to pump it's full capacity and either run itself dry or overflow your display tank (depending on your setup).

[yosemitesamiam]

First time poster, short time lerker...I registered not to bring back the dead (post) but to ask a question as this directly relates to me.

I just put together a 50 gallon aquarium (big black heavy duty tub) for my red ear slider. I decided to use a lying around 10 gallon aquarium as a sump/filter. I've got it in three sections, from drain is the pot scrubbers with filter floss on top. This pushes water under the first divider and into the center section, which is about 15-20 lbs of lava rock, then up over the wall to the third which is heat/pump. It's all outdoors...the turtle is over-wintered in the house as its way too cold here in Spokane, WA for that....ok off my own topic.

I purchased a 225-250 gallon/hour pump at Petco...I picked it because it has 6 feet of head. It is running 1/2" flex tube into a 3/4" ball valve/pvc setup into the top of the tank. The drain is also 3/4" which only makes a couple 90 degree turns then drops into the sump. I have a ball valve on the drain end as well.

I just got this all finally set up yesterday, and low and behold, the drain of course flows WAY faster than the pump can return it....I've got it turned down on the drain end by almost half. During feeding, I put a screen filter over the pipe end in the tank...then remove it so that particles can flow through. I do this during feeding as whole food chunks will block the half-cocked ball valve on the drain.

Now I read above that a valve on the drain is bad-juju...however I'm responding to this particular post for a reason. If at 3' head, your pump has 300GPH output, it still isn't enough to overcome the drain...for instance, 3/4" PVC will flow 660GPH under gravity feed...not being forced through the pipe at all. So are we saying for my little 50 gallon tank, I need to flow 660 gallons per hour after my 3.5 feet of head? (It's 3.5 feet from the bottom of my tank where the pump sits to the inlet on the Display tank). And wouldn't that be way too much flow in such a small sump?

Thanks for your time and patience guys! Really appreciate all your work here...and thanks for accepting a fresh water guy. ;)

Sam



Sure it is a "powerhead" :) at 6 feet of head, it has 0 output. At 3 feet of head it has 300GPH of output. That is, used as a "pump" it will likely never see more than 200-300GPH at the output. Restricting the "input" certainly limits the pump's ability to draw in water, but due to the design and low flow, cavitation is not likely. The "valve" on the inlet is part of the volute right at the impeller. Notice that the newer 1073.05 has a "smart" controller that shuts the pump off if the intake is blocked, and likewise adjusts the motor speed to control flow, no need to valve back the output.

Rest assured, valving back the output of a centrifugal pump is the PROPER way to reduce flow. The intake should NEVER be valved back to control flow.

With regard, to the Durso standpipe design (and with all due Respect to Richard Durso), I understand the physics of the design and how it works. In Richard's own words he explains he somewhat doesn't understand the physics, but just stumbled upon something that works for him.

The key point is that an "air assisted" standpipe (Durso, Sotckman, Hoffer, whatever) is only stable given the alignment of several environmental variables. If the "air" is used as the governor, then the system is at partial siphon and stability of the system is DEPENDENT on the regulation of the air. This style of standpipe is actually rather limited to quiet and stable operation over a small range of flow rates. Outside of that range (dictated by many local variables) the system will be either unstable, noisy and/or inject huge amounts of air into the discharge stream. This is far from ideal and again, a subject better left to a dedicated thread. My overflow project pages (and thread) have quite a bit of discussion on the subject, as does the "herbie" overflow thread.

:)

[yosemitesamiam]

I think maybe this post of mine above "tells" a lot of my experience with aquariums... LOL

Could I simply add a solid pipe 3/4" constant siphon to my system and overcome this issue of mine whereas the drain can quickly overcome the pump?

[Texas Paul]

The overflow of the tank controls a constant level inside the tank. All drains and the overflow box need to be sized to handle return rates higher than the pump output.

As long as it is sized this way, there is no need for any restrictions in the tank return or the drains. A constant level will be maintained in the sump, and the desired water level in the sump can be achieved with addition/subtraction of volume.

If you want the return rate to the tank slower for some reason, installing a valve on the output of the pump and partially closing it will achieve the lower rate.

Closing a valve on the outlet of the pump is the same principle as increasing the head height the pump has to work against. The pump can't tell the difference, the flow rate goes down and the pressure at the outlet goes up. Good Luck!

[tazdvl]

http://www.reefcentral.com/forums/showthread.php?t=1541946

It will sum up alot of good info, on regulating overflow-sump-tank questions.

[Rognin]

lol, the necro of this post is pretty hefty. It's 2 years old...

[SGT_York]

Yosmitesamiam. Your thought process is way off.

You need an overflow or raise the pipe inlet in your tank, drain flow does not determine display tank water height. A weir or pipe stand do. Read the thread above for sure.