# beginner at wet/dry. fill me in



## Ali1 (Apr 7, 2005)

So i've been doing alot of research about wet/dry filtration and have come to the conclusion that they are highly used for biological filtration. Now, what worries me is the concept of overflowing the tank itself or the actual sump. I've heard plenty of horror stories regarding tank over flooding and whatnot, so i was looking for some advice/suggestions to prevent from such situations happening and the reasoning in which a tank/sump overfloods. Currently, i have a 90G tank with 30G sump (external overflow box) that I purchased from someone. I had no idea these filters make a gurgling/splashing noise. I previously had a fluval 404 and rena XP3, so i never ran into noise issues seeing as how they were always inside the cabinet. if i understood correctly from my search, the overflow has to drain water faster than the pump returning water, otherwise the tank will eventually flood. (is what i said correct???) Am i missing anything else?

Appreciation in advance!


----------



## hidenseek (Nov 13, 2005)

yes you are correct about the overflow being faster than the pump. your water level in your tank will only drain to the bottom of your skimmer box or overflow. if your pump was faster you would overfill your tank unless you have it designed where your pump is at a level in your sump tank that it doesn't pump too much water back to the show tank.

if you've done as much research as you have said, then you should have come across how all of this operates. if not, then you need to research a little more because the info is out there in countless number of threads on different forums.

is your external overflow box a hang on contraption, or is your tank drilled? if you're just looking to get more bio filtration, then i would try out a FBF. you can find diy's on this too if you search for it.

honestly, i would stick with the fluval and xp3 if you still have them available.

hope this helps.


----------



## CICHnes (Jan 30, 2009)

If you are really concerned about overflowing the tank, put a ball valve on the return to the tank and control the return rather then worry about overflowing. Its easier to control the return then controlling the overflow. I'm currently running a hang on back over flow from CPR Aquatics and have had no issues about overflowing the tank or restarting the overflow during a power outtage (tested many times). If you're running a PVC overflow, then I would suggest adding a Tom's aqualifter on the top bend of the overflow where bubbles could build up and it be your guarantee it will restart on outtages and prevent bubbles from building up.

Hope that helps.


----------



## Ali1 (Apr 7, 2005)

I have the HOB overflow box. I start the process by inserting an airline tube thru the utube and suck the air out. As for the canister filters, I no longer have them. For the overflooding issue, to fix this issue I should extend the intake in the overflow box to be larger than the end of the utube, which essentially prevents overflooding when power outage occurs. currently, the height of the intake on the overflowbox( where the drips into) is lower than the end of the utube. Ill look into the standpipe to reduce the vortex noise. Anything else im forgetting????


----------



## CICHnes (Jan 30, 2009)

Are you able to post a pic of it, that way its easier to see it than visualizing it. Answers will be more accurate to help with your situation.


----------



## prov356 (Sep 20, 2006)

> the overflow has to drain water faster than the pump returning water, otherwise the tank will eventually flood. (is what i said correct???) Am i missing anything else?


No, not exactly, although I know what you're trying to say. The overflow has to have the *capacity *to drain 
everything that the pump pushes into the tank. The pump drives the flow rate, and the rates are equal, 
otherwise one or the other will flood. If the pump pushes 600gph, for instance, then the overflow and 
drain need to be able to handle 600gph. Make sense? The drain won't drain faster than the pump 
pushes water because it will only drain what's pushed into it by the pump.

So, the easiest solution is to get an overflow and drain that will handle more than the pump can 
push. Barring that, then the valve on the outflow side of the pump will work, but I prefer to just 
upsize the overflow rather than pull back on the pump.

Here's a good site that explains it pretty well.

Check it out and come back with more questions. Not sure why you're getting some of the responses 
that you are. There are many here willing to help.

Good for you on switching and going with the wet/dry. Don't go back to canisters. All of these 
issues can be worked out and you'll be better off.


----------



## Ali1 (Apr 7, 2005)

thanks prov.

makes sense now.

rather than making another thread, i bought a saltwater aquarium from an individual and plan on using it for freshwater. Do i have to go through the cycle all over again or is the bacteria in his bio-wheels still safe?? I scrubbed down the tank, rid the salt/hardness residue.


----------



## boredatwork (Sep 14, 2007)

prov356 said:


> No, not exactly, although I know what you're trying to say. The overflow has to have the *capacity *to drain everything that the pump pushes into the tank. The pump drives the flow rate, and the rates are equal, otherwise one or the other will flood. If the pump pushes 600gph, for instance, then the overflow and drain need to be able to handle 600gph. Make sense? The drain won't drain faster than the pump pushes water because it will only drain what's pushed into it by the pump.


There are some corner cases where the original statement is actually true.



prov356 said:


> Good for you on switching and going with the wet/dry. Don't go back to canisters. All of these
> issues can be worked out and you'll be better off.


I would modify that to say good for switching to a wet/dry...if you have a drilled tank. A sump on a non-drilled tank can be an extreme source of frustration. In my opinion a canister on a non-drilled tank is a superior option.

If you are looking to use an HOB overflow just beware that there is a very good chance you will not be happy with it. Of course, there are many who are, it just depends on what you are happy with. But there have been many many posts of people who were not - so I think its very important to be forewarned just in case.


----------



## Ali1 (Apr 7, 2005)

CICHnes said:


> Are you able to post a pic of it, that way its easier to see it than visualizing it. Answers will be more accurate to help with your situation.


yeah, here's how my current setup is.

http://s67.photobucket.com/albums/h317/ ... 4_0866.flv


----------



## bfg112 (Feb 13, 2009)

boredatwork said:


> prov356 said:
> 
> 
> > No, not exactly, although I know what you're trying to say. The overflow has to have the *capacity *to drain everything that the pump pushes into the tank. The pump drives the flow rate, and the rates are equal, otherwise one or the other will flood. If the pump pushes 600gph, for instance, then the overflow and drain need to be able to handle 600gph. Make sense? The drain won't drain faster than the pump pushes water because it will only drain what's pushed into it by the pump.
> ...


No, that is not true! Prov is exactly right. It is not possible for the overflow to drain more water than the pump is returning to the tank. I don't even know if this is worth arguing. It's ridiculous!


----------



## kodyboy (Dec 9, 2007)

yep, can't get water from nowhere, so you can not drain more water than is being pushed back to the main tank


----------



## sleepy09 (Jan 15, 2009)

> Prov is exactly right. It is not possible for the overflow to drain more water than the pump is returning to the tank. I don't even know if this is worth arguing. It's ridiculous!


I totally agree........

I have a 125 gallon reef ready tank with a 30 wet/dry filter. I know for a fact that the amount of water that drains into the overflows is the same amount of water that is pumped back into the tank by the pump that is located in the wet/dry.. There are only 2 ways for your tank to overflow, the first one is if there is some sort of blockage between the overflow drain and the wet/dry that doesn't allow for the water to drain. That blockage could be as simple as not having a large enough drain pipe that doesn't allow the water to drain fast enough to keep up with the pump. And the second is if the pump is way to large and it pumps more water into the tank than your overflow drain can/will allow. The trick here is to find a balance. You need to figure out how much water your overflows drain into the sump before you can figure out what size return pump to use.


----------



## CICHnes (Jan 30, 2009)

Thats why if you get a big pump, and who doesn't want a big pump. Put a ball valve on it, this way, a big pump doesn't have limitations unlike a small pump would. I'm using a Mag 12, I'm jus trestricting flow for the time being until I get my other tanks up and running so I can use the wet / dry as my central filter. If I had gotten a smaller pump, I wouldn't be able to push water to all 3 tanks that I want my wet / dry to filter.


----------



## Ali1 (Apr 7, 2005)

From what i've read so far, the issue with restricting the flow of your pump is it will put too much stress and eventually put your pump out


----------



## prov356 (Sep 20, 2006)

Ali1 said:


> From what i've read so far, the issue with restricting the flow of your pump is it will put too much stress and eventually put your pump out


I don't know that that's true even though I hear it often. I throttled mine back for a while with no ill effects. 
I think I'd need to see some manufacturer info confirming that before I'd go along with it. I know you 
should never restrict the intake, but never read anything from a pump manufacturer about the outflow.


----------



## CICHnes (Jan 30, 2009)

I've had my Mag 12's flow restricted for some time. No problems. Although, I will be letting her loose soon, when I get the other 40 G up and running, and it will be pumping to both tanks.


----------



## boredatwork (Sep 14, 2007)

bfg112 said:


> boredatwork said:
> 
> 
> > prov356 said:
> ...


I am not arguing, just pointing our a specific scenario when that is not true. If what you are claiming is correct then the phenomena known as the toilet flushing effect would not exist.

It is 100% possible for a drain to flow faster than a pump can return.


----------



## boredatwork (Sep 14, 2007)

kodyboy said:


> yep, can't get water from nowhere, so you can not drain more water than is being pushed back to the main tank


You are right. But you are only looking at half of the equation.


----------



## bfg112 (Feb 13, 2009)

Okay, I think I see what you are saying. The drain "wants" to drain more water than the pump is returning. Meaning the the drain may have the capacity to drain 600 gph, but maybe the pump only returns 400 gph. That is very true, and the drain should always have the capacity to drain faster than the pump can return to avoid overflowing the main tank.

However, if the pump is only pushing 400 gph, the drain only has 400 gph available to drain. So the equation is true. Water in = water out :thumb:


----------



## boredatwork (Sep 14, 2007)

When the two flow rates are in equilibrium that is true. While that is the case most of the time, it is not always true.

It will not be true at the very instant the overflow starts draining and it will not be true when there is any anomaly in the drain pipe behavior. The best example of this is the surging, or toilet, effect. If you are using a drainpipe with a vent, then it is easy to simulate. Just plug up the vent. What will happen is the drain will start to drain water faster than the pump can keep up because there is not air being sucked in. Water will be drained faster than the pump can return it, so the water level in the tank will drop below the overflow. Then it will have to wait for the return pump to fill the tank back to the overflow water level as the drain sucks in air to replace the vacuum in the drain pipe of the quickly drained water. Once the overflow level is met in the tank the drain will then quickly suck down water again until the level drop s below the overflow. This repeats endlessly until you unplug the vent.

The problem is that you are making a statement that the drain can only drain what the pump puts out. But that is not a statement but an observation in a particular scenario, that scenario being when the flow rates are in equilibrium. The observation will be different in a different scanerio.

So it is not a firm truth that the two flow rates are always equal, but it is true in a particular ( and most common) scenario.


----------



## bfg112 (Feb 13, 2009)

What you are saying is absolutely true. In a short period of time the drain can drain more than the pump is returning for that short period of time. But over the course of an hour, or two hours, or a day, the total drained is equal to the total pumped into the tank, making the flow rates equal. We're not doing calculus here. I'm not talking instantaneous drain rate. The average drain rate equals the average pump rate.


----------



## boredatwork (Sep 14, 2007)

bfg112 said:


> What you are saying is absolutely true. In a short period of time the drain can drain more than the pump is returning for that short period of time. But over the course of an hour, or two hours, or a day, the total drained is equal to the total pumped into the tank, making the flow rates equal. We're not doing calculus here. I'm not talking instantaneous drain rate. The average drain rate equals the average pump rate.


That was exactly the point. Once you qualify the statement to say average then it becomes true.

Or at least almost true. I would also append "in a normally operating system". If you had a sump that was not working correctly, then it is possible to observe an inequality of the flow rates.

While this has wandered far from the OP I still think its important to hash out these concepts until we get it right.


----------

