$15 PVC Overflow
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WildFoxMedia
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I built one of the more simple versions of this overflow and during testing, it works well. However, im concerned about only having one overflow - do you guys recommend having at least 2 intakes?
i see why yours is not working properly. it will work but the water level would have to rise approximately 1+ inch above your water current water level for it to start moving. by then you will have already shut off the pump cuase it looks as though you will overflow. if you look at the lowest part of the "+" fitting in the back (forgot the name of the fitting "Cross" i think), that is the line that the water lvl in your tank would have to exceed in order for it to overflow down the pipe. since you have it so high, it requires a higher water level that you have now. i dont know if that makes sense.
from your picture, the "cross" fitting appears to be even higher than you pipe you have on your tank. the water will flow once it exceeds the lowest part of the "cross" plus additional piping due to gluing. If it is true that your "cross" is higher than your pipe in the tank, then you water would have to rise to almost the top of the tank bracing. I think you will have to redo the pipe, but others can chime in.
for your observation, the attached is the modified dual overflow i will be using for my 75 with a incorporate larger skimming area. I will have to put something over it so fish dont fall in.
Look at the length of the "Cross" versus the highest point of the skimmer. there is several inches difference, hence water will pour in the overflow in side the tank, and the water pressure will equalize to the lowest point in the cross. once the water pours into the overlow over the highest point in the cross it will create a controlled siphon which will break when the water entering the overflow becomes less and below the hgihest point in the cross. hope that helps.
from your picture, the "cross" fitting appears to be even higher than you pipe you have on your tank. the water will flow once it exceeds the lowest part of the "cross" plus additional piping due to gluing. If it is true that your "cross" is higher than your pipe in the tank, then you water would have to rise to almost the top of the tank bracing. I think you will have to redo the pipe, but others can chime in.
for your observation, the attached is the modified dual overflow i will be using for my 75 with a incorporate larger skimming area. I will have to put something over it so fish dont fall in.
Look at the length of the "Cross" versus the highest point of the skimmer. there is several inches difference, hence water will pour in the overflow in side the tank, and the water pressure will equalize to the lowest point in the cross. once the water pours into the overlow over the highest point in the cross it will create a controlled siphon which will break when the water entering the overflow becomes less and below the hgihest point in the cross. hope that helps.
the overflow (single or double) works based on the equalization of water, assuming there is no air in the pvc pipes, then if you look inside the overflow pipe in the tank, you will see where the lowest part of the cross fitting is. if it is near the top of the overflow pipe, then you have the cross placed too high. it would need to be reduced. equalization of water is slower with smaller size pipe due to small amounts of pressure pushing the water from the overflow pipe. thats why if the cross is lower, then there can be several inches of water pressure pushing the water in the lowest part of the cross so that it can overflow, thereby allowing for greater gph activity.
if i think of a better discription, i'll post it for you if you still dont get how the overflow works. also, clamp the air value tubing so that no air can enter, those things do fair.
FWIW, i dont put air values on my overflow, i push water pipes from the JT fitting, in through the pipe and use a cheap pump to extract the air.
if i think of a better discription, i'll post it for you if you still dont get how the overflow works. also, clamp the air value tubing so that no air can enter, those things do fair.
FWIW, i dont put air values on my overflow, i push water pipes from the JT fitting, in through the pipe and use a cheap pump to extract the air.
wildfox, the reason people do the dual overflow is in case one fails. if you dont feel comfortable with one, then make two seperate of one with two overflows, which is what is presented in the beginning of this thread. i would recommend going with a bigger size pipe and doing the dual overflow, 2x the protection.
WildFoxMedia
New member
SuperNemo - I used 1" PVC and I feel confident with the flow its pushing through as it is, so the 2nd would be purely for the sake of emergency.
"then make two seperate of one with two overflows" - confused me. Are you referring to something that is like your design and ones posted earlier where there are 2 overflows that cross into 1 PVC pipe? Do you have 1 overflow higher then the other as a backup, or do you run both at the exact same height?
"then make two seperate of one with two overflows" - confused me. Are you referring to something that is like your design and ones posted earlier where there are 2 overflows that cross into 1 PVC pipe? Do you have 1 overflow higher then the other as a backup, or do you run both at the exact same height?
wildfox, i meant just make two overflows. should really reread what i write before posting. the overflow refers to the numbers of tubes you have in the water. the cross (or Tee) is just putting two overflow tubes into one tube that goes to the sump. sounds strange. theoretically if you have a big enough tube that goes to the sump (or smaller overflow tubes in the water, you could attach more overflows to the tube going to the sump. i.e. instead of a cross you can have a 5 way or 6 way fitting.
i like to run them both the same height. there is really no difference, except for the fact that the longer you have it, the more you could adjust the cross/tee if you make a mistake. i make the cross several inches lower so that there could be more pressure as water falls into the overflow tube, to push water over the cross into the sump, which would be faster. same theory as having a higher tank height cause more pressure/thicker glass, etc. from the original post, i believe that the short/longer overflow was just to save space cause they overlap each other.
zsqure, you can do that. it would also work; however, due to the fact that your elbows inside the tank are high, you cannot lower th cross in excess of the highest point on the elbows plus 1+ inche or so (safety factor) or else when the pump stops the equalization of the water in the tube will cause air to enter one of your overflow tubes. hope that makes sense. 2 1/2 inches looks okay from the picture, but can tell since there is no measurements. i'll take some measurements of the single overflow I have if i get a chance.
i like to run them both the same height. there is really no difference, except for the fact that the longer you have it, the more you could adjust the cross/tee if you make a mistake. i make the cross several inches lower so that there could be more pressure as water falls into the overflow tube, to push water over the cross into the sump, which would be faster. same theory as having a higher tank height cause more pressure/thicker glass, etc. from the original post, i believe that the short/longer overflow was just to save space cause they overlap each other.
zsqure, you can do that. it would also work; however, due to the fact that your elbows inside the tank are high, you cannot lower th cross in excess of the highest point on the elbows plus 1+ inche or so (safety factor) or else when the pump stops the equalization of the water in the tube will cause air to enter one of your overflow tubes. hope that makes sense. 2 1/2 inches looks okay from the picture, but can tell since there is no measurements. i'll take some measurements of the single overflow I have if i get a chance.
WildFoxMedia
New member
SuperNemo - The part that confused me was your broken *** engrish, so good work.
My question regarding multiple overflows was that it seems like you would want 2 completely separate overflows, that never meet - rather then 2 overflows in the tank that eventually connect. It seems like if something has the ability to block a single overflow, it could also block the tube to the sump after they connect and cause the same issue as having only one overflow in the first place.
My question regarding multiple overflows was that it seems like you would want 2 completely separate overflows, that never meet - rather then 2 overflows in the tank that eventually connect. It seems like if something has the ability to block a single overflow, it could also block the tube to the sump after they connect and cause the same issue as having only one overflow in the first place.
wildfox, that is true. two seperate overflows are better than one single overflow due to what you described above.
But to be technical on the subject of two overflows going into one tube, the tube going into th sump is actually larger than the overflow tubes. This is the only way that one tube going into the sump can accomidate the amount of water from two overflows. For that reason, what would cause a block in the overflow tube will not cause a block for the tube going into the sump. So for the dual overflow tube with one larger tube going into the sump would require only one tube to be block for it to not work instead of both overflow tubes being block at the same time. The reason for this is that originally it require two overflows to keep up with the return pump, but once one is blocked the other tube will not be able to keep up with the return pump.
This would not apply if the overflow tube can significantly flow faster than the return pump. Then even if one is block, the second could pick up the slack from the first.
But to be technical on the subject of two overflows going into one tube, the tube going into th sump is actually larger than the overflow tubes. This is the only way that one tube going into the sump can accomidate the amount of water from two overflows. For that reason, what would cause a block in the overflow tube will not cause a block for the tube going into the sump. So for the dual overflow tube with one larger tube going into the sump would require only one tube to be block for it to not work instead of both overflow tubes being block at the same time. The reason for this is that originally it require two overflows to keep up with the return pump, but once one is blocked the other tube will not be able to keep up with the return pump.
This would not apply if the overflow tube can significantly flow faster than the return pump. Then even if one is block, the second could pick up the slack from the first.
ambergris caye
New member
It looks like parasite in the "alien" movie that stuck impregnated someone.
okay, made some measurements of my pvc overflow. its 1.5 inch pvc. The overflow is 16.5 inch follow by two elbows, then the pipe going up and over the tank in 18 inches and two elbos, then down the outside of the tank is also 18 inches, then two elbows, up 9.5 inches to the tee. I have about 7 inches from the overflow which water flows into and then gets pushed out the tee. it is usually about 3-4 inches filled, so it creates a mini-siphon on the tee side as well. quite as it can be.
Note: i have a value on the pvc pipe going into the sump because the eheim 1262 does not even utilize 1/2 of the 1.5 size piping.
Note: i have a value on the pvc pipe going into the sump because the eheim 1262 does not even utilize 1/2 of the 1.5 size piping.
zsqure
New member
I added 3" to the tubes (dropped the cross piece 3") and things are flowing ok. Still not quite fast enough. I have a 3rd pvc overflow with no check valve in it as a back up. I'm going to remove the check valves and put in a on off valve.
thank you for your help.
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Joshnlaura
New member
Is there anyway someone can tell me what, where, and how that check valve works in this design? I havnt been able to locate anything that looks like that yet. Is that something that was made or bought in that 90 deg elbow assy?
RocketEngineer
Space is big.
The check valve at the top of the elbow is for evactuating the top of the siphon tube. Me, I replacecd the back elbow with a tee and used a plug with a drilled hole to mount the valve. An alternative is to use an adapter from the pipe size down to a small barb fitting that you can attach a piece of airline tubing to. The tubing allows you to pull the siphon while also being able to replace them when they wear out.
Hope that helps.
RocketEngineer
Hope that helps.
RocketEngineer
Rhodes19
New member
I'll have to give this one a try. I'm not quite sure how the siphon works but it looks like it would be a fum project to play with. 
Question, does pipes C and L have to go to the bottom of the tank? The few youtube videos I saw all have those pipes going to the bottom of the tank.
Question, does pipes C and L have to go to the bottom of the tank? The few youtube videos I saw all have those pipes going to the bottom of the tank.
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tiburone9162003
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