Newbie Overflow Issues

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Apollo7235

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Hello all,

I've seen this question pop up multiple times on this forum as well as others, however, the advice always seems to be different.

I built my own sump tank (scary, I know) and everything actually seems like it's fine (hallelujah). My issue began when we (dear hubby and I) began working on the plumbing (really scary, I know).

Relevant info, my display tank is 38-gallons and my sump is 20-gallons. My HOB overflow box is rated for 800GPH and my return pump is rated for 530GPH at 0', +/-325GPH at 4'-6 which is the height of the rim of my DT. We plumbed the overflow using 1"OD, 3/4" ID clear vinyl tubing, same for the return.

I opted for the 800GPH overflow because I wanted the added length on the skim. From everything I've read, an 800GPH overflow box should have absolutely no problem handling my pump, even at 530GPH, yet the pump chamber sucks nearly dry while my DT water level verrrrrrry slowly rises to nearly overflowing. I've tried playing with the skim box height on the overflow with no success. I am super scared to add more water to the system because I reaallly don't want to face an overflow. Silly me, I forgot to order a check valve, so we already experienced a near disaster when we originally set this thing up last night.

My return pump is not adjustable and I am really kicking myself for that. I suppose my question is, what now? Hahaha. I am soooooo frustrated. Should I go the gate valve route? Get a smaller or an adjustable pump? Or is there something I'm overlooking?

Any and all help is appreciated!
 
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Crustaceon

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Is this a siphon-style overflow with a clear acrylic “u-tube?” If so, you need to prime it by pushing an airline tube midway into the U, submerging it in the box and when you start the return pump, quickly sucking the air out of the tube and carefully removing the tubing without allowing air to shoot right back in.
 
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Apollo7235

Apollo7235

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Is this a siphon-style overflow with a clear acrylic “u-tube?” If so, you need to prime it by pushing an airline tube midway into the U, submerging it in the box and when you start the return pump, quickly sucking the air out of the tube and carefully removing the tubing without allowing air to shoot right back in.
Yes, this is a siphon-style overflow with the clear acrylic 'u-tube' and we did prime it in the way you are describing. The water does flow back down to the sump, it just isn't fast enough to keep up with my return pump for some reason.
 

Crustaceon

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Yes, this is a siphon-style overflow with the clear acrylic 'u-tube' and we did prime it in the way you are describing. The water does flow back down to the sump, it just isn't fast enough to keep up with my return pump for some reason.
Ok, aside from your return pump being too powerful (which I doubt) , another issue can be the depth of the water in the overflow box itself. Keep in mind, that tube relies on differential pressure to function properly and if the water level in the external box is too high, that tube has to not just transport the draining water through it, but push that addition external overflow box water out of the way, which can greatly affect overall flow. We’re going to go down the checklist here and check to make sure the water level in the tank-side box is higher than the water in the external-side box.
 

Crustaceon

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IF the water level is draining fast enough after the tube, then the problem is likely with the end of the drain line being placed too far under water in the sump chamber, which causes air within the line to slow down drain flow...which slows down u-tube flow. The fix for that is having that drain line terminate no deeper than 1” under water (1/2” is best IMO) in the sump chamber.
 
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Apollo7235

Apollo7235

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Ok, aside from your return pump being too powerful (which I doubt) , another issue can be the depth of the water in the overflow box itself. Keep in mind, that tube relies on differential pressure to function properly and if the water level in the external box is too high, that tube has to not just transport the draining water through it, but push that addition external overflow box water out of the way, which can greatly affect overall flow. We’re going to go down the checklist here and check to make sure the water level in the tank-side box is higher than the water in the external-side box.
Thank you so, so much for taking the time to guide me through this.

Yes, the water in the external overflow box is lower than the water in the internal box. I just ran the system a few times to make 100% sure of that.
 
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Apollo7235

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IF the water level is draining fast enough after the tube, then the problem is likely with the end of the drain line being placed too far under water in the sump chamber, which causes air within the line to slow down drain flow...which slows down u-tube flow. The fix for that is having that drain line terminate no deeper than 1” under water (1/2” is best IMO) in the sump chamber.
I am super excited that you just said this!

The return tube is about 6 inches underwater, so I will shorten it to only an inch and report back! I had suspected this previously, but thought that since it was only 6ish inches that it wouldn't be enough to cause an issue.

Wahooooooo, fingers crossed that this is the fix!!

I will report back as soon as I have a moment to cut the tube. Thank you, again!
 

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Also wanted to add that you mentioned having a problem with the sump overflowing when return pump was disconnected due to not having a check valve. While a check valve is a nice addition they do fail and in your case if power to your pump is lost and your valve fails you will have a flood. Ideally you want enough extra space in the sump to accommodate all the water that backflows. This can be remedied by adding a siphon break to your return line.
 
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Apollo7235

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Also wanted to add that you mentioned having a problem with the sump overflowing when return pump was disconnected due to not having a check valve. While a check valve is a nice addition they do fail and in your case if power to your pump is lost and your valve fails you will have a flood. Ideally you want enough extra space in the sump to accommodate all the water that backflows. This can be remedied by adding a siphon break to your return line.
Thank you for responding!

When only the water that is in the return line flows back into the sump, I have no overflow issues. It's only when I turn off the system and the DT water back-siphons into the sump. You do have a great point about the check valve's potential to fail, though! I will certainly look into adding a siphon break as well; anything I can do to prevent an overflow disaster, I will absolutely do it!

Thank you so much!
 

theMeat

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3/4” ID is not going to handle more than 400gph on drain in the best of conditions.
For return line it’s under pressure and can pump 3x that.
Don’t know what overflow box you have but gonna guess it’s got a one inch bulkhead if it’s rated 800gph.
If you don’t want to run pvc get one of these.

Can likely find one at your local pool supply too.
This will slide snug into the bottom of bulkhead on overflow box
 
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Apollo7235

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3/4” ID is not going to handle more than 400gph on drain in the best of conditions.
For return line it’s under pressure and can pump 3x that.
Don’t know what overflow box you have but gonna guess it’s got a one inch bulkhead if it’s rated 800gph.
If you don’t want to run pvc get one of these.

Can likely find one at your local pool supply too.
This will slide snug into the bottom of bulkhead on overflow box
Thank you for responding!

Yes, my overflow box has a 1" bulkhead. I just ordered the 3' version of that hose as well as a spare bulkhead just in case the first one gets damaged during our disassembly. Unfortunately, I couldn't find the 4 footer on Amazon and I really need this thing up and running ASAP, so waiting on longer shipping isn't an option. I think the 3 footer should be long enough, but we shall see!

Thank you so much for your help! Hopefully, between the new hose and the adjustment to the hose height, this thing will work out!
 

Imaexpat2

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Also wanted to add that you mentioned having a problem with the sump overflowing when return pump was disconnected due to not having a check valve. While a check valve is a nice addition they do fail and in your case if power to your pump is lost and your valve fails you will have a flood. Ideally you want enough extra space in the sump to accommodate all the water that backflows. This can be remedied by adding a siphon break to your return line.

And How!!!! One of the very reasons I run fairly large sumps on my systems compared to the size of the display its serving.

To the OP:

I am a older guy, kinda like Joe Biden just not as bad and I am easily confused and you have been most successful at that! Let me see if I have this straight....You have a over flow rated at 800 gph that flows water into your sump. You have a sump pump rated at 530 gph with no account for the head it has to over come. Your problem is the display is filling up faster than water going back to the sump is happening and your sump where your return pump is almost running dry? Is that correct? If thats the case sounds like you got a design issue in your sump! I just dont see how you could have an issue with a 800 gph over flow and a 530 gph return....if anything you should be having issues maintaining a siphon or at least serious noise issue from gurgling water and air in you over flow to the sump to my way of thinking.

I am running a 10 gallon sump on a 20 gallon tank with a CPR over flow rated at 350 gph. I am running a 550 GPH adjustable pond pump from Home Depot rated pump with about 2' 3" of head. I am also running a Aqualifter pump on my CRP over flow to reduce the chance of loosing siphon due to air bubbles building up in the over flow box and breaking my siphon. I got no issues and it works like a champ. Dont see why you should be having issues if you set the sump up correctly.
 
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Apollo7235

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And How!!!! One of the very reasons I run fairly large sumps on my systems compared to the size of the display its serving.

To the OP:

I am a older guy, kinda like Joe Biden just not as bad and I am easily confused and you have been most successful at that! Let me see if I have this straight....You have a over flow rated at 800 gph that flows water into your sump. You have a sump pump rated at 530 gph with no account for the head it has to over come. Your problem is the display is filling up faster than water going back to the sump is happening and your sump where your return pump is almost running dry? Is that correct? If thats the case sounds like you got a design issue in your sump! I just dont see how you could have an issue with a 800 gph over flow and a 530 gph return....if anything you should be having issues maintaining a siphon or at least serious noise issue from gurgling water and air in you over flow to the sump to my way of thinking.

I am running a 10 gallon sump on a 20 gallon tank with a CPR over flow rated at 350 gph. I am running a 550 GPH adjustable pond pump from Home Depot rated pump with about 2' 3" of head. I am also running a Aqualifter pump on my CRP over flow to reduce the chance of loosing siphon due to air bubbles building up in the over flow box and breaking my siphon. I got no issues and it works like a champ. Dont see why you should be having issues if you set the sump up correctly.
Hi there, thank you for responding.

Yes, you do have that correct and yeah, actually, the overflow is gurgling now that you mention it, but the siphon is maintained. I had honestly thought that this was a normal occurrence and that, once I got everything running properly, I could spend some time quieting things down.

When I built the sump, I did quite a bit of research on how to build it correctly, but considering I’ve never done it before, there’s definitely a huge margin for error. One thing I actually just thought about is that I’ve been testing the system without the protein skimmer in the first chamber. That being said, I feel like that amount of water displacement might actually make a solid difference. I am going to run everything here shortly with the shortened tubing and the skimmer and see how it goes.

I’ll report back with the results.

Thank you so much!
 

Imaexpat2

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Okay if you got air gurgling in your hose going from the over flow to the sump, you aint moving enough water. Its common for there to be a little air gurgling in the line going to the sump from the over flow but it shouldnt be significant. In my set up its almost unnoticable.

I am still confused tho how you could possibly be using an under sized return pump with such a huge over flow box and have rising water in your Display tank. But then again I use a CPR Overflow box and not a U-Tube siphon, so maybe I am missing something.
 

Crustaceon

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Okay if you got air gurgling in your hose going from the over flow to the sump, you aint moving enough water. Its common for there to be a little air gurgling in the line going to the sump from the over flow but it shouldnt be significant. In my set up its almost unnoticable.

I am still confused tho how you could possibly be using an under sized return pump with such a huge over flow box and have rising water in your Display tank. But then again I use a CPR Overflow box and not a U-Tube siphon, so maybe I am missing something.
This can absolutely happen. The problem is created when the volume on the tank side can’t develop enough pressure to overcome the pressure in the overflow box and subsequent drain outside of the tank. If you put a hose over the rim of the tank, hold it lower than display level and draw the air out, a siphon will he created due to the pressure differential. The same holds true for her overflow box setup and that’s what we need to recreate at least from the beginning to the end of the U-section.
 
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Imaexpat2

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This can absolutely happen. The problem is created when the volume on the tank side can’t develop enough pressure to overcome the pressure in the overflow box and subsequent drain outside of the tank. If you put a hose over the rim of the tank, hold it lower than display level and draw the air out, a siphon will he created due to the pressure differential. The same holds true for her overflow box setup and that’s what we need to recreate at least from the beginning to the end of the U-section.
Okay I am 10-4 on that now as I clearly understand now exactly whats going on without the benefit of seeing it in action. Makes perfect sense. I guess becuase I have always used CPR over flows with a Aqualifter Pump I havent been able to duplicate that issue in my tanks.
 

Crustaceon

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3/4” ID is not going to handle more than 400gph on drain in the best of conditions.
For return line it’s under pressure and can pump 3x that.
Don’t know what overflow box you have but gonna guess it’s got a one inch bulkhead if it’s rated 800gph.
If you don’t want to run pvc get one of these.

Can likely find one at your local pool supply too.
This will slide snug into the bottom of bulkhead on overflow box
Personally, I think the 3/4” drain is totally fine for that amount of flow because no matter what, the moment that drain line is filled with water and covered up in the box, it’s going to go full-siphon and far exceed the flow of her pump.
 

Crustaceon

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Okay I am 10-4 on that now as I clearly understand now exactly whats going on without the benefit of seeing it in action. Makes perfect sense. I guess becuase I have always used CPR over flows with a Aqualifter Pump I havent been able to duplicate that issue in my tanks.
I’m thinking there’s a “finger” on the end of the hose somewhere that’s partially blocking the flow, lol. Pardon my analogy.
 
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Apollo7235

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Okay if you got air gurgling in your hose going from the over flow to the sump, you aint moving enough water. Its common for there to be a little air gurgling in the line going to the sump from the over flow but it shouldnt be significant. In my set up its almost unnoticable.

I am still confused tho how you could possibly be using an under sized return pump with such a huge over flow box and have rising water in your Display tank. But then again I use a CPR Overflow box and not a U-Tube siphon, so maybe I am missing something.

This can absolutely happen. The problem is created when the volume on the tank side can’t develop enough pressure to overcome the pressure in the overflow box and subsequent drain outside of the tank. If you put a hose over the rim of the tank, hold it lower than display level and draw the air out, a siphon will he created due to the pressure differential. The same holds true for her overflow box setup and that’s what we need to recreate at least from the beginning to the end of the U-section.

Okay, so here are the results of my testing:

I removed enough hose to raise it to only 1/2" below the waterline in the first chamber. I also added the protein skimmer to see what would happen with additional water displacement. The results were much better than before, but still not where they need to be.

Upon some further investigating, it looks like what @theMeat suggested is the most likely issue. When we plumbed the overflow with the 3/4" ID, 1" OD vinyl tubing, the output was reduced, therefore reducing the effectiveness of the overflow box. We are going to swap out the tubing for the drain hose @theMeat suggested and see what happens. Seriously crossing my fingers that this solves our issue! I'm probably going to run to Home Depot later today to see if they have one of those drain hoses so we don't have to wait until Sunday to see what happens.

I sincerely appreciate all of your help and suggestions and I am absolutely open to any and all further advice! Thank you all again!
 

theMeat

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Personally, I think the 3/4” drain is totally fine for that amount of flow because no matter what, the moment that drain line is filled with water and covered up in the box, it’s going to go full-siphon and far exceed the limits of her pump.
Without a secondary and a valve to regulate the “full siphon” there won’t be a full siphon. It will fluctuate between full siphon and not with water level in overflow box going up and down. This will be associated with gurgling
 
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