Balancing Flow

[mark.wittig]

I have a recently cycled 180gal DT with a DIY 40 gal breeder sump. I have 1" drain lines from two overflow boxes draining into the sump. I have 2 1" return lines going back to the DT via the 2 overflow boxes. My pump is a little underpowered to match my drain flow so I have to adjust drain flow using ball valves. I know. I plan on getting a dart in a few months so I can have fully open drain lines. For now, I have to get things stabilized.

I dial back the drains with return pump unrestricted (i.e. valves fully open) until flows are pretty evenly matched. I am guessing I have about 1000gph going. I then use a gate valve that returns water to sump to allow me to fine tune return flow to match drain flow. I have found it difficult to reach equilibrium between the drain and return flow resulting in low water in return area and air cavitation until water stabilizes again. I can sit there for an hour have it dialed in, water level in return stable, and then sometime during the day or night the water level will fall again. Any ideas on what is going on?

I thought it might be evaporation but I have ATO via Apex and there shouldn't be enough evaporation in a few hours to result in this. Appreciate any thoughts and insights. All plumbing lines are new and clear of obstructions.

[matt144]

I had a similar problem on my 65gallon. I was told that there was friction in the lines which caused uneven flow and that I had to allow some non-photosynthetic algae to build up.

[mark.wittig]

Did that work?

[billdogg]

without going to a full siphon, the most your 1" drains will handle is ~300 - 350gph each, for a total of 700gph max. You should not have any restrictions at all in your drain. If they can't handle the flow, put a valve on the output of your return pump to reduce it. Restricting a drain is nothing more than a flood that has not happened yet.

For the Dart you plan on - I have one and love it. I have 2 x 2" and 2 x 1" drains on my 150g. I also tee the return off to feed my 120g refugium and 2 x BRS reactors.

JM.02

[mgoblue]

Mark - or anyone else -

I am confused. If the return pump is undersized for the overflows, then why would you have to gate valve the overflow? Wouldn't it only return what was pumped into the DT?

Just trying to learn something here....

thanks!

[mark.wittig]

Originally Posted by mgoblue

Mark - or anyone else -

I am confused. If the return pump is undersized for the overflows, then why would you have to gate valve the overflow? Wouldn't it only return what was pumped into the DT?

Just trying to learn something here....

thanks!

Ball valves don't provide the same level of flow control as gate valves do. I had to dial back drain flow with ball valves to match the return flow going back to DT. The gate valve is on one of the return lines over the sump. This allows me to "fine tune" return flow to match with drain flow by dumping some return back to sump. I found it easier to adjust drains first to get it close to return flow. Then I can send some flow back to sump from return lines if pump is slightly out of tune with drains to maintain stable water levels in the return area.

By the way, closing valve on outlet side of pump can reduce its life. Dart pumps can sense back pressure from a valve and adjust flow accordingly without impacting pump life and will also reduce electricity consumed.

[steamman]

I too am confused. Why would you restrict the water coming from your overflows to your sump? Maybe I am reading this post wrong. Is this how you are operating your system basically? My crude diagram only shows one line coming back from your DT and I think you said you have two.

[mark.wittig]

Originally Posted by steamman

I too am confused. Why would you restrict the water coming from your overflows to your sump? Maybe I am reading this post wrong. Is this how you are operating your system basically? My crude diagram only shows one line coming back from your DT and I think you said you have two.

I have two overflow boxes, one in each corner. There is a 1" drain line coming from each overflow box to my sump for a total of two 1" drain lines. I have a 1" line running from sump to an external pump that pumps water back to the DT through two 1" return lines that split off a tee on pump outlet. These two 1' return lines return water via those same two overflow boxes.

My drain flow is higher than my return pump. Return pump is rated at 1800 gph at 0'. Drains are via 1 1/4" durso stand pipes that drain at ~ 600 gph per pipe. I estimate head loss resulting in return flow at about 900 - 1000 gph. So, right now I have an underpowered return pump that would result in water levels in overflow boxes falling below intake of standpipes if drains were left wide open. This would result in variable levels in those overflow boxes. So I have partially closed ball valves I installed directly beneath bulkheads on drain lines (installed so I could do maintenance) to reduce drain flow to vicinity of 1000 gph - something my return pump could keep up with. Well, it is difficult adjusting flow with ball valves. So if you adjust ball valves to flow slightly lower than return flow rates, you can use a gate valve on a return line to return a small portion of return flow back to sump instead of DT. The gate valve is easier to adjust than the ball valves. That is why I have gate valve on return line capable of returning water to sump. If I didn't, the return pump will drain more water from sump that drain lines are delivering resulting in a drop in the water level in the return area of the sump. This then results in air intake into pump, cavitation, and air bubbles in the DT.

I hope this explains what I am doing. Either way, I haven't been able to get the drain flow and return flow balanced and stabilized so my levels are all stable and water in DT is crystal clear.

[steamman]

Bare with me here. I am trying to follow. I have a fair amount of experience in piping flow rates head pressure and friction loss. I kind of do this for a living. I am not a PE. I am hands on. Thirty two years.
Are your overflows loosing siphon in any scenario?
Do you have a picture of your overflows you can post? Pictures of your sump and piping perhaps?
You should be able to bypass some of your DT water back to the sump and find a balance there. Restricting your overflows is not the way to go IMHO. That is an accident waiting to happen. A valve on your overflows for maintenance reason is OK. But I have to question using them to balance your system.

This is if I am following you correctly.

[mark.wittig]

Originally Posted by steamman

Bare with me here. I am trying to follow. I have a fair amount of experience in piping flow rates head pressure and friction loss. I kind of do this for a living. I am not a PE. I am hands on. Thirty two years.
Are your overflows loosing siphon in any scenario?
Do you have a picture of your overflows you can post? Pictures of your sump and piping perhaps?
You should be able to bypass some of your DT water back to the sump and find a balance there. Restricting your overflows is not the way to go IMHO. That is an accident waiting to happen. A valve on your overflows for maintenance reason is OK. But I have to question using them to balance your system.

This is if I am following you correctly.

Here you go. I can only upload 5 photos. Right overflow is same as left overflow. Lines closest to tank ends are drains with ball valves. Lines towards inside are return lines. Durso standpipes are 1 1/4" in overflow box. Drain lines from bulkhead are 1" to sump. Return lines are 1" all the way to 3/4" loc-line. I am a physicist actually by training but fluid dynamics and plumbing are not my thing. I work in explosives.

If I recall correctly pipe friction is a larger contributor to drag than elbows, valves, etc. I did eliminate 90 degree elbows but as you can see space in tank stand is a premium and it is difficult getting everything to fit. The larger the pipe diameter the more difficult it is - particularly for the return lines. I prefer rigid piping over flex because I believe the cons outweigh the pros - I cannot afford a major leak in my finished basement. Or at least my hobby cannot afford my wife's wrath . I want to reduce algae inside pipes, etc.

Bottom line: I can't seem to tweak it so sump levels are consistent with exception of evaporation. I plan on switching to a dart pump in future that handles head pressure better. The master blaster pump you see is rated to 1800 gph at 0' but cover is cheaply made and prone to small leaks due to vibration - hence the towel in the photo. You may note I have had to epoxy the outside cover a number of times to address leaks. It is a stop gap measure for now. Holes in bottom of tank are for 1" and 3/4" bulkheads so I am limited there - not much else I can do with this 180 gal oceanic. I don't want to drill holes in back either. I should be able to get this thing working reliably without modifying the tank further and potentially degrading its structural integrity.

[steamman]

To fix leaks on pumps due to vibration just add a small flexible connector on the inlet and outlet of the pump. This will help eliminate noise as well as stress on the pump.

Flex connectors are common practice in my trade. I always use them in this hobby as well. Just because they are smaller doesn't mean the same rules don't apply. I am not the only one that uses flex connectors at the pumps.

This may sound like a dumb question but do you have a vent hole on top of your Durso standpipes? I couldn't see that from your photos.

[RocketEngineer]

Ok, back to square one.

From what you have described, I'm not sure you understand how an overflow works.

http://www.melevsreef.com/allmysumps.html

With the pumps off, the water level inside the tank should be just below the level of the overflow boxes. As the pump starts, it begins pumping water into the display, therefore raising the level in the display until it tops the overflow box. The pump continues to transfer water from the sump to the display but now the water is filling the overflow box. Once the box is full to the level of the standpipes, the standpipes allow the incoming water to drain back into the sump. Once the amount of water draining down the stainpipe equals the amount that the pump is transfering to the display, the water levels in the three volumes should not change.

The part of this system that is important is having enough drain capacity to handle what the return pump is pushing into the tank. This can be accomplished by having a large enough drain to handle the pump, or by restricting the pump OUTLET to reduce the amount of water it pushes into the tank to less than the upper limit of the drains.

If the water level in the oveflow boxes is fluctuating, then you are pushing more water into the tank than the standpipe can handle normally. The rising water in the overflow box eventually gets above the air inlet on the drain and a siphon starts which can handle much more flow. Because the siphon can move so much more water, the siphon drains the overflow box until it pulls in air and the siphon is broken. This cycle of filling the overflow box, a siphon starting and the siphon breaking causes a lot of noise and will cause the water level in the sump to fluctuate. If this is what you are seeing, the restriction you have placed on the drain is causing the drains to be a siphon all of the time. If something were to restrict the flow in the drain at this point, the drains wouldn't be able to handle the outflow of the return pump and you will either run the pump dry or more likely overflow the tank.

There are two systems that use a siphon in a drain setup: the Herbie method and BeanAnimal's overflow. The herbie method uses two lines and runs the same risk of a blockage causing a flood. BeanAnimal's has a third dry pipe which is a safety and would accept the flow from the siphon if something were to clog the pipe.

http://www.reefcentral.com/forums/sh...d.php?t=344892
http://www.beananimal.com/projects/s...ow-system.aspx

Based on what I see of you're system, you are using a single drain in each overflow box. SO, remove any valves you have on the drain lines. Make sure the standpipes are set up properly. If standpipes are the Durso design, you may need to adjust the air hole. If the tank is still filling faster then the drains can empty it, then the solution is to restrict the pump outlet until the drains can handle the inflow.

You have all the pieces you need to make this system work. I hope that you will take a serious look at the pieces involved and reconsider the restrictions on the drains. They are a failure waiting to happen. It is my hope that this can be prevented with a little information.

Long and detailed, but I hope it helps.

RocketEngineer

[steamman]

Originally Posted by RocketEngineer

Ok, back to square one.



The part of this system that is important is having enough drain capacity to handle what the return pump is pushing into the tank. This can be accomplished by having a large enough drain to handle the pump, or by restricting the pump OUTLET to reduce the amount of water it pushes into the tank to less than the upper limit of the drains.

IMHO I believe restricting the flow on the pump discharge makes the pump work harder than it has to. In your photos you have a bypass back to your sump. Personally I would have put this tee for the bypass in before I branch out to my return. In your case you have two from what I make of it. I feel opening this valve until you reach the desired flow might be a better method of regulating how much water is returned to your DT.

It does seem that RocketEngineer has come to the same conclusions I have come to. The only difference we have is the way to regulate the flow to your DT.

[RocketEngineer]

steamman,

It depends on the pump but in most cases there is a range of head values that allow the pump to work the most efficiently. This depends on the pump itself and the head it is working against. In some cases, a venting line will reduce energy usage by decreasing back pressure but another pump in the exact same setup you would be better to restrict the flow on the outlet of the pump to increase back pressure. There are a lot of variables involved in this stuff.

In my case, the return to the sump provides the the flow to the refugium. I have a valve on the outlet of the return pump at about half closed that reduces the flow coming out of the pump and into my manifold. From there a second valve on the refugium supply adjusts how much goes to the refugium with the rest going to the display.

Different methods for different setups.

RocketEngineer

[mark.wittig]

All,

Thanks for the input so far. I actually looked at Melev's web site as I put everything together. The sump is designed to hold water during normal operation and additional water from drain lines, return lines, and overflow boxes (water level from overflow slits to standpipe entrance) and not flood. The only things I don't think I did correctly are 1) I did not drill holes in my loc-line and 2) I did not start everything up correctly - I should have filled tank up to overflow slits (but not over them), filled overflow up to standpipe inlets, filled sump, and then turned on return pipe and opened up the drains. I will try that. Would a small return area volume in sump also complicate this? My return area is only 7" high because flow comes from my protein skimmer area that can only be between 6"-8" high for optimized performance.

I still note that discussions are about matching return flow that is higher than drain flow. I have what appears to be the opposite problem. My drain flows are higher than my return flow. Should I adjust the holes on top of the standpipes more? I agree the ideal situation is to open drain valves fully and adjust return accordingly. I will try to adjust my water levels during my water change later today or this week, start up everything correctly, and adjust standpipe holes and see what happens. Fixing this will also let me shut return pump line off for feeding and enable easier start up.

Any more thoughts? I appreciate the patience. I was supposed to have someone from my local club help walk me through this during setup and operation but everyone gets busy and they were not available.

With respect to alternative drain setups:

Herbie method: the picture links don't work anymore so it is difficult to fully understand but I think what he did is use both overflow bulkheads - 1 for drain and 1 for safety drain. He removed top of standpipe near overflow slits, put strainer on it, and left it open. He put other standpipe open in what is typically the return bulkhead at higher height so if main drain line is clogged, water rises in overflow and begins to drain via emergency drain line. He returns water to display over back top of tank. Do I have it right? I would prefer not to run return lines external to tank footprint for aesthetic reasons, maintenance (only 6" clearance to wall), and to minimize potential for damage to wall.

Beananimal method: This method won't work because my tank is setup differently and I would prefer not to run lines external to the tank footprint.

[mark.wittig]

Thanks to everyone for your input and patience. I was able to get everything working. I reset water levels during water change this week. Rocket Engineer's post got me to revisit Melev's site and recall some of that advice. I took everyone's advice and fully opened ball valves to drains. What I had previously failed to do was adjust the siphon holes on top of the durso standpipes. Once I did this the flows were easy to match via my gate valve off the return pump. My sump levels are now very stable and working perfectly.

I hadn't completed that part of the durso standpipe setup properly. As a result, the overflow levels were dropping too fast and the drains would stop, the return pump would pump water out of the return area until air cavitation started. When water was pumped into display tank, the water would fill overflow area but drain fast again. I simply solved the problem the wrong way by partially closing the ball valves. This made it harder to match the flows. Also why my description of the problem was counter intuitive to the seasoned vets! Slowly increasing the size of the hole on top of each durso standpipe worked. The water levels in the overflow areas are very stable. An note for other newbies like me, the hole sizes in top of each durso standpipe are likely not to be the same size due to differences in the plumbing underneath. My left overflow drains right to the sump. Its flow travels through pipe the least with no elbows. As a result the hole in the top of that standpipe was larger than the hole I put in the right side where water must travel about 4 ft through a couple of 45 degree elbows.

Thanks again everyone!