PVC overflow

[FDdragon]

So i have been looking at some overflow systems. Just for my knowledge, if someone was to build a system as such....
http://www.reefcentral.com/forums/showpost.php?p=4088699&postcount=46
is there a lenght that the pipe inside the tank that the pvc pipe needs to be?

I saw a video on youtube about this and it looks like it will work fine, just curious if the pipe needs to be all the way down to the bottom of the tank or can it be shorter (with adjusting the rest of the pipe to still have siphoning)

Just curious because we might make this for my buddy's tank since it is low cost. Thanks!

 

[mcgyvr]

Guess what happens if that overflow ever gets clogged or the flow is reduced enough..

 

[uncleof6]

Do a search for "diy pvc overlfow," on this forum. What you will find posted, by folks that actually understand the dynamics of drain systems, is these devices have very low flow capacities (lower than practical for marine systems) and they do not work as advertised. The folks posting positive outcomes with these devices, really have no idea of the actual flow rate of their system, (and it is always WAY over-guessed) or they are very tolerant of the issues (no surface skimming, problems consistant with a dursol or other open channel drain system, etc.) created with these devices, unless the flow rate is extremely low. The dynamics of these devices are quite complicated, for one short post.

You will be time, and money ahead (if you do not wish to, or cannot, drill the tank,) to purchase an HOB overflow from a suppliers such as LifeReef (high quality.) They are far from "ideal" overflow/drain systems, but they will outperform any conceivable "diy pvc overflow," the drawback is they are not cheap. However, the drain system is not the place, to try, to save money. Search RocketEngineer and BeanAnimal specifically.

 

[racer14j]

I have used one similar to that for over 3 years on a 29 gallon tank and a frag tank with no problems. I also have one on a 75 that I started 4 months ago with no issues. Like any other part of the tank it will need cleaned. I clean mine every 6 months or so. My design is made a little different than the one in your link but the idea is the same. If you would like I could post some pics and go into detail about mine later this weekend. to answer your question all of mine touch the sand. Everything I found show that will help water move faster, but I have not tested that my-self.
It is also worth noting I just like D.I.Y. I spent the same on my first one as a store bought by time I got it right.

 

[FDdragon]

Sorry for the late reply. I am in a location where internet is a hit or miss.

Thanks for the information. I was planning on trying a system like this in my buddy's tank (we are limited to what supplies we get where we are currently at) and use two overflow setups to have one as a safety backup. We also have some aquatic screen type pieces that we can screw at the end to prevent anything big coming in.

From other information i have found, the length of the pipes impact the flow rate (the longer the pipe, the slower) so we will try different sizes and see how that works.

If all else fails then we will look at finding a legit overflow system that can be sent to us.

Thanks again! Ill keep you guys posted.....but this project wont be until a while later.

 

[KCFITZ78]

Here is a modified PVC Overflow I have just built. http://www.reefcentral.com/forums/showthread.php?t=2353384

Here is some info I found on the PVC Overflows (not my data, this is what I referenced):

Cross Sectional Area (in square inches) - Pipe sizes vs. their cross sectional area. Useful for dividing flow between pipes.

size __area
1/2 = .1963
3/4 = .4418
1.0 = .7854
1.25= 1.227
1.5 = 1.767
2.0 = 3.142

Maximum Gravitational Vertical Flow - This is what we look for when sizing drains or DIY overflows. The flow under the power of gravity reaches a maximum in the same way an object reaches Terminal Velocity as it falls through the air. The gravitational force is countered by the waters viscosity (resistance to flow) and the frictional resistance of the pipe. The viscosity creates a minimum vertical length to acheive the maximum flow. If the vertical pipe length is less than the minimum, the flow rate will be somewhat less than the pipes maximum potential.

size _GPM __GPH
1/2 = 2.50 = 150
3/4 = 5.63 = 337.5
1.0 = 10.0 = 600
1.25=15.6 = 937.5
1.5 = 22.5 = 1350
2.0 = 40.0 = 2400

Min. Vertical Length
1/2 = 2"
3/4 = 5"
1.0 = 9"
1.25= 14"
1.5 = 20"
2.0 = 36"

Frictional Head Loss per 90 (measured in Feet of Head)
size_ head loss
1/2 = .00970
3/4 = .00220
1.0 = .00386
1.25= .00602
1.5 = .00878
2.0 = .00156

Anyway... Each measurement is at the pipes maximum flow rate in the Vertical Flow Rate chart. When calculating the loss for the pump side, these values are slightly more.

There is a very conservative rule when estimating head loss. It is one foot of head per fitting. This rule does not take into account flow rates, pressure, actual frictional losses, etc. It does not have to because it is too conservative. If you multiply any of the above head losses by one thousand fittings, you will be very surprised at the actual head loss. (hint: just move the decimal to the right three places.)


Gravitational Horizontal Flow This is for horizontal applications that do not rely on a pump, or the force of a vertical pipe. These flow rates are considerably less than the vertical rates because gravity does not offer a significant horizontal force. It is a balance of gravity and the viscosity vs. the cross sectional area of the pipe.

size_ GPM
1/2 = 1.563
3/4 = 3.517
1.0 = 6.253
1.25= 9.769
1.5 = 14.07
2.0 = 25.0

In this application, you would use the chart for Vertical Flow.

In this application, you would use the chart for Horizontal Flow.

PVC Losses ---> http://www.engineeringtoolbox.com/equivalent-pipe-length-method-d_804.html

PVC Fitting Losses ---> http://www.engineeringtoolbox.com/pvc-pipes-equivalent-length-fittings-d_801.html

 

[FDdragon]

Yeah, the first pic you have is what we are going to make. Still utilizing two of them just in case. Awesome, thanks.

 

[KCFITZ78]

Yeah, the first pic you have is what we are going to make. Still utilizing two of them just in case. Awesome, thanks.

Did you make any progress with your overflow? Mine is different than what you were going to do. I did not like the design so I changed it. I am curious to find out what you did.

 

[seove]

Since the check valves have a tendency to leak/fail you may want to add something like this. This is my temporary fix until I find something else.

http://www.reefcentral.com/forums/picture.php?albumid=10118&pictureid=70185

 

[ericarenee]

Since the check valves have a tendency to leak/fail you may want to add something like this. This is my temporary fix until I find something else.

http://www.reefcentral.com/forums/picture.php?albumid=10118&pictureid=70185

The best thing to do is hook the check valve to a toms uplift pump. It will constantly pull some water thru that valve so no air can get trapped there. Some manufacturer over flow boxes recommend using a uplift pump with them as well. Since your u tube over the top of the tank cant be seen for air trapped i would NOT Do a diy pvc overflow without a uplift pump..

 

[Captain smoke]

Personally for chances of getting clogged and loosing a siphon I would get a Eshopps HOB overflow for 60$.