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Guams
Joined: 21 Aug 2009
Location: Wisconsin
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 Posted: Wed Nov 04, 2009 11:06 am Post subject: What size pump for a wet/dry? |
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I'm in the building stages of a wet/dry filter, and one of the last parts I need to figure out is... what size water pump will I need?
Here's what I've got so far:
Display tank = 55 gallon (standard footprint)
Wet/Dry = 30 gallon
I'm using a skimmerless overflow design from the library, therefore the water from the display tank will flow, via siphon, into the overflow. From the overflow, it will drain (by gravity) through 1" PVC into the wet/dry. Once in the wet/dry, the water will flow into drawer #1 of a Sterilite set-up. This first drawer will house the mechanical filtration (poly-fil and another more porous material) and will be drained by a series of holes drilled into the bottom of the drawer. It will then make it's way into drawer #2 which will have the bio-filtration (pot scrubbers). In the second drawer, I cut out most of the bottom and the pot scrubbers are resting a piece of eggcrate for drainage.
From drawer #2, the water flows into the 30 gallon tank, where it will be heated and pumped back into the display tank. And because of the size, it may or may not become a plant refugium in the future.
I've read that 1" ID PVC will drain anywhere in the neighborhood of 300-600GPH. But according to FlexPVC's (http://flexpvc.com/WaterFlowBasedOnPipeSize.shtml) charts, 1" PVC will drain 960GPH when gravity fed.
So... my question for you folks is: What's the correct flow-rate for 1" PVC? AND What size should my water pump be?
Here's a quick drawing of my plans... sorry it was done is MS Paint.  I didn't want to take the time to draw it in Google Sketch-up.
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Neogenesis
Joined: 03 Jan 2008
Location: Findlay, Ohio
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| Posted: Wed Nov 04, 2009 11:15 am Post subject: |
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I'm using 1" vinyl tubing into my wet/dry, am using a ViaAqua 2300 and it does a fine job. When it does finally bite the dust I plan to buy a higher quality pump, but it provides good flow for now.
Scott
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redblufffishguy
Joined: 16 Jul 2009
Location: Red Bluff, CA
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| Posted: Wed Nov 04, 2009 11:30 am Post subject: |
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With no friction loss, 1" PVC can handle 16 GPM, or 960 GPH. however, with a minumal amount of loss, you could easittly get 20-23 GPM (1200-1380 GPH) through the pipe.
It appears that you are olny asking the pump to lift the water a few feet, so you really don't have much head to worry about.
If it were me, I would use a 800-1200 GPH pump. you do have enough lift that some of the flow will be lost, and you can always add a valve in the return to limit the flow a bit. |
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Guams
Joined: 21 Aug 2009
Location: Wisconsin
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| Posted: Wed Nov 04, 2009 12:04 pm Post subject: |
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| redblufffishguy wrote: | With no friction loss, 1" PVC can handle 16 GPM, or 960 GPH. however, with a minumal amount of loss, you could easittly get 20-23 GPM (1200-1380 GPH) through the pipe.
It appears that you are olny asking the pump to lift the water a few feet, so you really don't have much head to worry about.
If it were me, I would use a 800-1200 GPH pump. you do have enough lift that some of the flow will be lost, and you can always add a valve in the return to limit the flow a bit. |
That's correct, all I need for the pump to do is lift the water from wet/dry back into the main tank. I forgot to mention in my OP that the head height will be between 3 and 4 feet.
So, using 800-1200GPH, I won't have to worry about running the pump dry at all? |
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redblufffishguy
Joined: 16 Jul 2009
Location: Red Bluff, CA
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| Posted: Wed Nov 04, 2009 12:31 pm Post subject: |
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That is why I suggested a valve on the return after the pump. You can partially close it to allow less flow to return to the tank. With a little trial and error, you can get it dialed to the point where you have exactly the same amount to water leaving the tank as entering it.
Partially restricting the flow should not harm the pump at all, but if you are worried, add a Tee in the return and put the valve on the tee. The extra water can be directed through the tee and right back into the sump. Using the tee will allow the pump to run at open flow without pumping the total volume of water directly to the tank.
Another option is to use a larger pipe size coming out of your tank. 1-1/4" PVC for example will allow for 25 GPM (1500 GPH) gravity flow. So if you use it, you will effectivly have more coming out than going in. The only problem there is that you can get too much coming out and loose your siphon, or overflow your sump. That method works best when the tank is drilled. In the case of a drilled tank, there is no need for the valve on the return line. You simply pump the water in, and once it reaches the level of the drilled overflow (granted it must be able to accomodate the flow) the water will pour out. The beauty of the drilled over flow is that you will ALWAYS have the same amount of water leaving the tanks as is being pumped into the tank, and by default, the sump will not go dry. |
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mithesaint
Joined: 30 Oct 2006
Location: Buffalo NY
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| Posted: Wed Nov 04, 2009 12:41 pm Post subject: |
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| redblufffishguy wrote: | With no friction loss, 1" PVC can handle 16 GPM, or 960 GPH. however, with a minumal amount of loss, you could easittly get 20-23 GPM (1200-1380 GPH) through the pipe.
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Wait...what? I may have misread that...but are you saying that the water flows faster WITH friction loss than WITHOUT? I'm no expert on fluid dynamics, but that sounds backwards. Please clarify/explain please.
To the OP, I've always used 600 gph as my rough estimate for 1" PVC, right or wrong. That's for a DIY overflow too, not a skimmer box. Not sure if that makes any difference or not. Anyway, I don't have my sump anymore, but when I did, I used two 1" DIY PVC overflows paired with a Quiet One 4000 pump. My pump wouldn't pump anywhere near what the PVC would flow, but that was fine with me. I wanted to make sure my overflow capacity was redundant in case something stupid happened like a dead fish or other debris blocking/slowing the overflow to the point that the sump runs dry or the tank literally overflows.
For me, I probably would have been fine with a QO 4000 at 5 ft head with a single PVC overflow, but adding the second overflow made it idiot proof. I'm a talented idiot, after all. 
Good luck! |
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redblufffishguy
Joined: 16 Jul 2009
Location: Red Bluff, CA
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| Posted: Wed Nov 04, 2009 1:08 pm Post subject: |
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when you add pressure to the water flow, the GPM increases. However, with the incresased flow, you gain friction loss.
Pressure flow and gravity flow work a bit differently. The pump will be pushing the water under pressure, and the overflow with be gravity. That is why i mentioned the two different flow rates. |
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Guams
Joined: 21 Aug 2009
Location: Wisconsin
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| Posted: Wed Nov 04, 2009 2:18 pm Post subject: |
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| mithesaint wrote: | | To the OP, I've always used 600 gph as my rough estimate for 1" PVC, right or wrong. That's for a DIY overflow too, not a skimmer box. Not sure if that makes any difference or not. Anyway, I don't have my sump anymore, but when I did, I used two 1" DIY PVC overflows paired with a Quiet One 4000 pump. My pump wouldn't pump anywhere near what the PVC would flow, but that was fine with me. |
I suppose this is what's confusing me. How do I make sure I don't A) overflow my sump and B) overflow my tank?
My assumption is that with the skimmerless overflow, water will stop moving between the tank and overflow when the water levels equalize (standard siphon behavior), thus preventing me from flooding the sump. But a gut feeling is telling me that I'm incorrect because of the water pressure when pulling the water from the bottom of a 55 gallon tank. Maybe I'm just over-evaluating it. 
So let's see if I can get this correct. From the tank to the sump, I should expect anywhere in the neighborhood of 600-950GPH and from the sump back to the tank, I should have a pump rated higher than the input? Should the return volume be too much, I just divert some water back into the sump?
Oye, it seems that when I take stuff out of my head and put it on paper it gets much more confusing. |
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redblufffishguy
Joined: 16 Jul 2009
Location: Red Bluff, CA
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| Posted: Wed Nov 04, 2009 2:39 pm Post subject: |
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| You have it exactly. Chage the volume diverted back into the tank intil the tank output matches the flow into the tank! You can check by monitoring the level of water in the sump (or the tank). once it stays constant, you are were you need to be |
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KaiserSousay
Joined: 02 Nov 2008
Location: PartlyCloudyFlorida
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| Posted: Thu Nov 05, 2009 4:15 am Post subject: |
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A Big 
On a way to redirect any excess flow back to the sump, as well as getting a pump that is a bit more than you think you need.
Most of the time, price differences between flow amounts, are only a few dollars for the higher flow pump. Money well spent.
Most people use a PVC ball valve for their sump projects, I would suggest the use of a gate valve instead. The ease of making fine adjustments without the frustration of trying to move the ball valve a little this way and that. A little more money, but again, money well spent.
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Guams
Joined: 21 Aug 2009
Location: Wisconsin
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| Posted: Thu Nov 05, 2009 11:24 am Post subject: |
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Who would have thought it's so friggin' hard to find a 900-1000GPH pump in stores. I've called several places and nobody has anything in stock. I've got today, tomorrow, and most of Saturday off and I'd let to get moving on this thing. 
Eh... I've got a couple other places to call, but they don't open for a little while yet.
/end rant |
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redblufffishguy
Joined: 16 Jul 2009
Location: Red Bluff, CA
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mithesaint
Joined: 30 Oct 2006
Location: Buffalo NY
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| Posted: Thu Nov 05, 2009 4:08 pm Post subject: |
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| redblufffishguy wrote: | when you add pressure to the water flow, the GPM increases. However, with the incresased flow, you gain friction loss.
Pressure flow and gravity flow work a bit differently. The pump will be pushing the water under pressure, and the overflow with be gravity. That is why i mentioned the two different flow rates. |
OOhhhh....I thought you were only referring to the overflow rates. Didn't realize that you were talking about pressurized return lines. Thanks. |
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mithesaint
Joined: 30 Oct 2006
Location: Buffalo NY
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| Posted: Thu Nov 05, 2009 4:37 pm Post subject: |
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| Guams wrote: | | mithesaint wrote: | | To the OP, I've always used 600 gph as my rough estimate for 1" PVC, right or wrong. That's for a DIY overflow too, not a skimmer box. Not sure if that makes any difference or not. Anyway, I don't have my sump anymore, but when I did, I used two 1" DIY PVC overflows paired with a Quiet One 4000 pump. My pump wouldn't pump anywhere near what the PVC would flow, but that was fine with me. |
I suppose this is what's confusing me. How do I make sure I don't A) overflow my sump and B) overflow my tank?
My assumption is that with the skimmerless overflow, water will stop moving between the tank and overflow when the water levels equalize (standard siphon behavior), thus preventing me from flooding the sump. But a gut feeling is telling me that I'm incorrect because of the water pressure when pulling the water from the bottom of a 55 gallon tank. Maybe I'm just over-evaluating it.
So let's see if I can get this correct. From the tank to the sump, I should expect anywhere in the neighborhood of 600-950GPH and from the sump back to the tank, I should have a pump rated higher than the input? Should the return volume be too much, I just divert some water back into the sump?
Oye, it seems that when I take stuff out of my head and put it on paper it gets much more confusing. |
There are two ways to handle this issue, neither is right or wrong. To each their own. It's impossible to perfectly match a pump and overflows without adding valves, etc so either the pump or the overflow will move more water.
I prefer to have my overflows move more water, so I had two overflows and a smaller pump. To me, that decreases the possibility of overflowing my tank due to a overflow malfunction. If one overflow gets plugged or loses siphon, I still have the other to prevent my tank from overflowing. It saves me money on the initial pump purchase, and saves me money on electricity down the road.
Others prefer to have a bigger pump, and to put either a bypass to the sump to re-oxygenate the water or simply a valve on the return line to slow down the flow to match the overflow. I don't like this approach for two reasons. First, it costs more to buy the pump, and costs more to run the higher GPH pump over time. Secondly, if something happens to the overflow and flow rate slows, you're more likely to overflow the tank. The nice thing about this approach is that if you upgrade to a larger tank later, your new pump might work for that tank too.
Neither way is right or wrong. What makes sense to you, and works for you is the right way for you.
A properly configured system that is properly refilled after a water change won't overflow the sump.
Put it together, and start messing with it. That's the only way to find out how it will work. Just have a few towels handy just in case
Hope that helps. |
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fox
Joined: 10 Jun 2009
Location: East Coast, USA
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| Posted: Thu Nov 05, 2009 10:20 pm Post subject: |
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I tend to use a larger pump and divert back excess flow. It makes for a quieter system.
The system needs to be balanced. If you pump more than your overflows can handle you will need to divert the excess. You can benefit by using this excess to pass thru a UV sterylizer or just allow it to refilter in the drip tray. Cleaner water and more oxygen.
If you overflow more than you can supply you will need to slow down the drain or live with the noise of a cavitating drain. No biggie just restrict the drain and noise goes away. But then you are not getting the amount of flow and added advantages of more turnover of the water collumn. So get another smaller pump and now you can open the drains to compensate. Not a good investment if you had just used a larger pump in the first place.
The larger pump is not a big difference in price when you shop around. I use 600 GPH for 1" PVC as a starting point, though a 1" PVC pipe might flow more under gravity once you add an elbow and or valve you lose some of that flow. |
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