Continuous overflow systems??

[b2bwest]

I don't have a pre-drilled tank, and I want to set up a sump/refugium. Can anyone point me to a site - or explain how a continuous siphon overflow system works - such that it doesn't overflow the sump or the tank if something screws up? Are some better than others?
I don't want to tear down the tank to get it drilled.

 

[rcoultas]

The overflow box will only siphon down the top inch or so of the tank and can only do so at the rate that the return pump puts it back into the tank. You must have a check valve on the return line so as not allow it to become a siphon in a power outage.

 

[earlybird]

check valves are not necessary if you allow enough room in your sump for backwash and one your return line you have a hole drilled just below the water level so that it will break siphon. In a power outage your overflow box with U-tube will retain just enough water to keep the U-tube filled. When power kicks back on your return pump will start filling the tank again and then the water will rise and fall back into the overflow box and gravity and pressure will get the U-tube working again. Very simple physics.

 

[b2bwest]

Thanks. Are any brands better than others - or are they all the same?

 

[earlybird]

CPR is a big brand but you have to look around to find the different style which I prefer over CPR because you don't need an air pump to keep the siphon going. I bought mine at my LFS for $25. It's custom though but it's hard to mess up the design. Similar to the one below.

 

[tarball]

Something else to consider in the continues overflow system is the return pump. Its extremely important that the return pump flow equal the flow coming from the overflow to the sump.
Lets say you have 500 gph coming through the overflow to the sump. But the return pump is only pumping 400 gph back to tank. This will leave an excess flow of 100 gph flowing to sump from tank, which will overflow the sump.
It will be very difficult to exactly match the pump flow to the overflow coming from tank. So you will need to add a ball valve between the overflow & the sump. That way you can throttle back the flow from the overflow to match the pump flow per hour back to tank.
Its critical to match flow coming from tank & returning to tank.
Git it...

 

[b2bwest]

I was told you couldn't overflow the sump, because if not enough returned to the tank, the level would drop below the overflow weir and stop flow to the sump.
More worried about pumping the entire contents of the sump up into the main tank - but I guess if you put a weir in the sump, that would stop flow to the return pump if the sump wasn't getting enough water. But the pump would likely burn out if I wasn't around to catch it. Hmmm.

 

[scotts]

With all due respect to Tar..... uh he has it backwards. Your pump returns the water from your sump to your tank. So you cannot get 500 gph going to your sump if you are only putting 400 gph into your tank. Also you would not want to put a vavle between your overflow and your sump. The main problem that people have with sizing things is sizing the pump to the overflow. You should put a valve on the outlet of your pump in case you need to slow it down to not overflow your tank, or suck all the water out of your sump.

 

[badboyj]

Originally Posted by earlybird
check valves are not necessary if you allow enough room in your sump for backwash and one your return line you have a hole drilled just below the water level so that it will break siphon. In a power outage your overflow box with U-tube will retain just enough water to keep the U-tube filled. When power kicks back on your return pump will start filling the tank again and then the water will rise and fall back into the overflow box and gravity and pressure will get the U-tube working again. Very simple physics.
that's how you do it!!

 

[dawman]

Originally Posted by Scotts
With all due respect to Tar..... uh he has it backwards. Your pump returns the water from your sump to your tank. So you cannot get 500 gph going to your sump if you are only putting 400 gph into your tank. Also you would not want to put a vavle between your overflow and your sump. The main problem that people have with sizing things is sizing the pump to the overflow. You should put a valve on the outlet of your pump in case you need to slow it down to not overflow your tank, or suck all the water out of your sump.

Exactly !!

 

[b2bwest]

Thanks all - I think I'm going to give it a try. Hopefully I get it right - I don't need a flood & some dead fish.

 

[tarball]

Originally Posted by Scotts
With all due respect to Tar..... uh he has it backwards. Your pump returns the water from your sump to your tank. So you cannot get 500 gph going to your sump if you are only putting 400 gph into your tank. Also you would not want to put a vavle between your overflow and your sump. The main problem that people have with sizing things is sizing the pump to the overflow. You should put a valve on the outlet of your pump in case you need to slow it down to not overflow your tank, or suck all the water out of your sump.
Grumble:

..... I will explain tomorrow.

 

[tarball]

Originally Posted by Scotts
With all due respect to Tar..... uh he has it backwards. Your pump returns the water from your sump to your tank. So you cannot get 500 gph going to your sump if you are only putting 400 gph into your tank. Also you would not want to put a vavle between your overflow and your sump. The main problem that people have with sizing things is sizing the pump to the overflow. You should put a valve on the outlet of your pump in case you need to slow it down to not overflow your tank, or suck all the water out of your sump.
Hello Scotts

I finally have some time to jot some thoughts down.
1st. I'm not sure why someone would want to close down a valve on the outlet of a pump to control flow. I understand that its done. But why? all that does is cause the pump to operate under more pressure. Which in turn causes the pump to wear out faster. Common sense says to me the pump should run at full flow with least amount of back pressure.
2nd. I have a overflow very similar to the photo above. Its a 700 gph which is a bit large for my 55g but I wanted it in case I decided to up the size of my tank. I also added a Rio 1700 pump which moves 440 gph back to DT from sump. The pump turns the tank over 8 times per hr, & turns the sump over 34 times per hr. This is my target flow per hr.
I have a 1inch bulk head fitting on the bottom of the overflow & a 1inch bulkhead fitting at the sump. Between the 2 I have a 1inch hose with a 1inch ball valve.
If my tank is full as it should be & the sump is 2/3rds full also as i like to keep it & the pump is running at full flow. If I open the 1inch ball valve to full open. Within 5 minutes my sump will fill up & overflow. That's a fact, the overflow does not care how much water the pump is moving. All its doing is siphoning water from the DT tank to sump. Now grant it, the pump is moving 7.5 gallons a minute back to the DT. But over a few minutes I will see a displacement of water from DT to sump because of a greater flow from overflow which is 700 gph vs 440 gph. Remember all it takes is 7 gallons of displaced water from DT to overflow sump.
If I throttle back the 1inch ball valve to match pump flow I can have a even flow back & forth from DT to sump. & also allow my pump to operate at full flow with minimal back pressure which will maximize the life of the pump.
Plus having a ball valve between the overflow & sump & ball valve between the pump & tank, will allow me to shut them off & separate the sump from DT for cleaning using unions.
oh by the way I have a 20g sump

 

[ameno]

I have valves on both the supply and pump return just so I can have control over what flows were. but best case is to have all valves at full open. You will only flow out the amount of water that your pump puts into the tank. Say your pumping 900gph back to the tank, you will only overflow 900 gph back out. if you start closing back on the sump supply you will raise the water level in your tank. which may cause your sump to overflow in the case of a power outage or pump failer. In cases were your overflow is not enough to keep up with the pump then you cut back the flow on the pump return. Most all pumps are made to handle some back pressure without damaging the pump. In any piping desing flow control valves are used on the pump discharge to control flow rates. So the best set-up is to have your overflow handle more then you pump, design your flow rate on your pump flow rate and leave all valves at full open. Hope this makes sense.

 

[scotts]

Hey Tar.
First off it sounds like we can agree to disagree about pressure wearing out a pump. Although here is a thread that someone asked about throttling back a pump. https://www.saltwaterfish.com/vb/showthread.php?t=286271 Basically I do not think it is a problem.
So with that being said I find it easier to control the flow going into the tank, and knowing that is the flow that is going to go back to my sump. That way when you make any adjustments, you are dealing with the level in your tank, and not your sump. Pretty hard to overflow the sump that way because you are only returing the water to the sump as fast as you are pulling it out.
I agree with you about the valves and unions. The maintenance guys used to get sick of me telling them you cannot have too many valves in a line. Although since I am using my old 55 gal as the sump for my 125 I have my pump going over the side of my 55. If I need to pull my pump out, I just literally pull it out, no problem.

 

[tarball]

I agree with both of you guys. There's nothing wrong with closing a valve down at the outlet of a pump. I'm very aware they build the pumps to handle some back pressure. But my thinking was directed at gph which is something i wanted at full flow.
Minimal operating pressure to do a job with optimal flow is the way I think. I'll explain..
I've been in the fluid power business for more then 27 yrs. In other words, I work with hydraulics. I've been designing & building hydraulic systems for more then 20 yrs. During this time I've built or repaired systems that operated from 3 gallons to 200 gpm & pressure systems from 3000 to 5000psi
Inside my head when I think about flow & pressure, I think build the system that will function correctly with the least amount of gpm flow & pressure. That way things operate
cooler ,smoother, with less heat added & less stress to all components & plumbing.
If theres one thing I've learned is there are many different ways to accomplish the same thing.
But, when I decided to build the sump. I decided I wanted the pump to run fully open using 3/4 line which is appropriate for 440 gph flow & more. Just for the record I have a 3/4 ball valve also plumbed into the return for several reasons. But my intentions are to allow the pump to run at full flow because I want 440 gph.
Can the pump handly back pressure if I decide to cut back flow

you bet. But this is something that I do not want to do.
I find it just as easy to control flow from the DT to sump with slight adjutments with the ball valve returning to sump.
This situation keeps my DT full at all time & most evaporation from DT is seen in the sump. Which is where it should be seen. I have a line drawn on the sump & all I have to do is fill to line and i'm good.
Just for the record, I have no problems when I have a power out. I have maybe 3 gallons max from DT to sump & when power returns I have all water levels return to normal.
Its just like noted above, we should design the system around the pump with its flow at full operation. This is how I think, doesn't mean anyone else is wrong. Its all good.

if we do things a bit different that's fine. Just means were thinking a bit different.
I've learned a lot from people that think differently then me.
Like I said, its all good & I respect yours & others opinions..

 

[scotts]

Tar,
There is a flaw in your logic. If your pump is pulling from your sump at the rate of 440 gph and putting it into your DT at the rate of 440 gph, then the only amount of flow that you can have going through your overflow and back to your sump is 440 gph.
So if in a static position all of your levels are full, your DT is full and your sump is 2/3 full and you turn your pump on, then the flow rates will be equal and your system will be in balance and you will not have to restrict anything and there is no way that you will have an overflow.
I know your overflow is 700 gph, but you are only supplying it at the rate of 440 gph.

 

[tarball]

Lets say you have 500 gph coming through the overflow to the sump. But the return pump is only pumping 400 gph back to tank. This will leave an excess flow of 100 gph flowing to sump from tank, which will overflow the sump.
Ok, finally have some time to sit down & make some retractable remarks...

First I would like to say the Quote I made above is incorrect.
oops sorry,

. ... The over flow box should stop the sump from over flowing.

 

[tarball]

Originally Posted by Tarball
If my tank is full as it should be & the sump is 2/3rds full also as i like to keep it & the pump is running at full flow. If I open the 1inch ball valve to full open. Within 5 minutes my sump will fill up & overflow. That's a fact, the overflow does not care how much water the pump is moving. All its doing is siphoning water from the DT tank to sump. Now grant it, the pump is moving 7.5 gallons a minute back to the DT. But over a few minutes I will see a displacement of water from DT to sump because of a greater flow from overflow which is 700 gph vs 440 gph. Remember all it takes is 7 gallons of displaced water from DT to overflow sump.

OK, once again I have misspoken, The sump will not overflow if I open the 1 inch ball valve completely. The overflow will stop the sump from overflowing... hehehe, sorry about the false info...

 

[tarball]

Originally Posted by Scotts
Tar,
There is a flaw in your logic. If your pump is pulling from your sump at the rate of 440 gph and putting it into your DT at the rate of 440 gph, then the only amount of flow that you can have going through your overflow and back to your sump is 440 gph.
So if in a static position all of your levels are full, your DT is full and your sump is 2/3 full and you turn your pump on, then the flow rates will be equal and your system will be in balance and you will not have to restrict anything and there is no way that you will have an overflow.
I know your overflow is 700 gph, but you are only supplying it at the rate of 440 gph.

OK Scotts
When I open the 1inch ball valve completely open. The overflow begins to empty. Not totally, but the rear box outside tank empties, almost to the point of breaking syphon. Overflow empties to the same point as if I cut the s/r pump off.
Also the overflow box inside the tank empties 1 to 2 inches below the inlet slots at the top of the box.
So what I get is water flow noise coming from inside box of overflow & the outside box of overflow makes constant slurping noise because of low water levels. If I add water to DT its displaced to sump & not returned to DT.
I took your advice about shutting pump off, & I also closed off ball valve. Filled DT up, Filled sump up to proper level.
I then started pump back up & opened 1inch valve to full open.
Once again water displaced to sump, & the overflow became very low causing problems mentioned above. Also lowered water level of DT.
Fact is, if I open ball valve to full open. The overflow runs like crap. But if I back flow up with 1inch ball valve between sump & overflow. The overflow remains full & the tank remains full.
& I still get full flow from pump in sump.
Why would i want to change things?