Need to decide on a pump for my tank. I dont want any circulation pumps in the tank itself, so all water movement needs to come from the pump itself.
its a 60 gallon 24x24x24 tank with 2 1 inch return and 1 1 inch intake. I have a small 384 mazzei for CO2, a 540 OC cannister and the biggest pentair mechanical filter - all in parallel. Plus plumbing to fit all of that plus heater and a small chemical module into a small stand.
Does anybody have any idea how much head that is?
The tank stand is pretty tall at 4' feet, and the actual outlets will probably be atleast another half a foot above the stand hight. So I figured thats around 4' head. Plus around 1.5 feet for all the plumbing turns(or is it more? there is alot of plumbing). I figured that the mazzei plus the pleat filters should add another 2 feet to head, so I was thinking I am looking at atleast 8'. Am I right? is it more or less?
Right now I have a reeflo gold dart that I will probably return - it seems abit too noisy. I was thinking of getting a red dragon pump - the tank is in a room where I would like it to be quiet if possible.
How much flow should I have and how much head loss would I have with the stuff that I have in there? I was aiming at x15 times the tank an hour, which is about 1000gph after head loss.
Despite all this, something tells me I might have more head loss than I think, when the pleat filters get some stuff on them, closer to 10'.
Also, I do have pressure guages on the filters - and with no media whatsoever they show about 3.5psi when the mazzei is halfway open.

What do you guys think my goal flow should be and what head loss should I account for?
BTW, on a side note, its very fun to hit about 10pbs co2 with the mazzei turned on full pressure and a 3600gph pump - the bubbles come out as dust clouds.

Thanks,
Chris.

I recently learned that canister filters mounted below the aquarium don't use their head pressure in getting water up to the top of the aquarium. This may seem ridiculous, but it is true. I always wondered about this from the way a Rena Filstar XP3 primes itself. That is done by having the canister filter empty of water, sitting below the tank, the inlet and outlet hoses disconnected from the filter and shut off. You then pour water into the inlet hose until it is full. Plug in the pair of hoses to the filter and open the shutoff valves. The slug of water in the inlet line drops down to the filter, sucking water over the top of the tank, and establishing the siphon. From then on the water just flows down to fill the filter, and continues to flow until the entire outlet hose is also filled with water. No power, no pressure, nothing but gravity fills the outlet hose back up to the top of the tank. This led me to make the following:


You can see from this, that the pump in the canister filter does nothing except move water. Its head pressure is used only to overcome line restrictions, not to raise water back to the top of the aquarium.

So, re-evaluate your needed head pressure, omitting the height of the tank from the equation. The head will only be used to overcome line resistance, and the line resistance will reduce the flow rate from the filter because as the filter pump output pressure rises in response to that resistance, the flow has to drop to keep the pump within its power rating. (Pump power = pressure across the pump times gallons per minute through the pump.)

Vaughn, thanks for the response, however I dont think you are right about this.
First, this is NOT a canister pump. Hight DOES matter in pump preformance, whether its canister or not. Just because it primes itself(this is simple gravity combined with suction, this is how syphon works, however, water wont circulate on its own, so when a pump drives water up, it still needs to do the hard work Pump pressure is usually much more than the pressure created by 60 gallons of water 3 feet above. If you read instructions for any canister filter, it will tell you that its not intended to use with more than 5' length of tubing. Pleat filters cause more head loss, and clogg up faster, I dont intend to clean often, which is why I over filter for a 60 gallon.

If you use a sump located below the tank, and it is an open sump, not a closed circuit device like a canister filter, the pump does have to push the water back up to the tank. Then, the head produced by the sump pump must be used both to overcome pipe resistance and the height of the tank above the sump. But, a canister filter, if primed, will have the water already up to the tank above, so no pressure is needed to do that. Even a pumpless canister filter, like the OceanClear filters, is a closed circuit filter, with the water already siphoned back up to the tank, so all that filter's pump needs head pressure for is to overcome the line and filter resistance to flow.

Try to work out how a canister filter can self prime, with the pump off, if the pump is needed to push the water back up to the tank, remembering that the pressure in the canister is equal to the height of the tank above it, even without the pump running.

vaughn,
The filter can self prime, when there is air in the lines, however, if there is an air pocket in the plumbing somwhere - it wont self prime, unless the psi created by the water is high enough.
In my system, the PSI created by water pressure up top is around 1 PSI, which is relativly low.

In other words, water pressure coming in from the tank does not always equal the pressure you must overcome as you pump water up.

Imagine you had a canister filter, with 20' of vertical plumbing. most canister filters would not be able to pump very much water at all, even though its a closed system. GPH is directly effected by distance pumped.

In any case, how much head loss do you think I would have due to an OC 340 filter and a big(36") pentair mechanical module?

Most canister filters wouldn't be able to pump through 20 feet of plumbing, whether it was vertical or horizontal. The friction losses in the plumbing would be too great. It takes 'H' feet of head to raise water 'H' height. If the water lines are full of water, the filter pump 'H' feet below the tank is at 'H' head, so all the pump has to provide is enough additional head to overcome the resistance to flow that is from the piping, the filter media, the reactor, the UV, the heater, or whatever else is in that plumbing. If there is an air bubble in the filter return line, most filters won't be able to pump at all, because they can't produce the pressure needed to raise the water back to the top of the tank. Priming means to eliminate those air bubbles throughout the filter system.

Since I don't have an OC filter, nor the module you mentioned, I don't know what head is needed to force water through them. I think the manufacturers would provide that information.

Ntino,

1 psi = 2.3' of head.


That is true to an extent, but the distance isn't the key so much as the water velocity through the pipes. Pipe friction increases exponentially as water velocity through the pipes goes up. The water velocity is determined only by the plumbing size and the flow rate, not the length of pipe. You can pump 1000gph of water through 2000' (yes that's two thousand feet) horizontally (or up and down through a closed canister system) with a 3" diameter pipe with less pump flow losses (your pump would see 2' of system head) than the losses you would have pumping that same 1000gph of water for only 10' through a 3/4" diameter pipe(your pump would see about 8' of system head).

I think the issue that is being run into is that there are actually four main types of head in plumbing systems, and most people only talk about and calculate for one of them. There is "static head" which is the resistance of gravity. It is caused by there being a difference in height between the input and output of your system. Vaughn is right, in your case that is zero since you have a closed system. There is "pressure head" which is the resistance to flow through things like filter elements, bio-media, etc. It is the energy it takes just to get the water through a pleated filter (for instance) at a certain flow level. There is "velocity head" which is calculated based on how fast the water leaves the system outputs when returning to your aquarium. The last one is "resistance/friction head". That is the resistance to flow caused by the internal resistance of the plumbing itself due to the number of bends you have, pipe size, etc. These three are a little trickier to calculate, because they are flow specific. An increase in flow through the same system will increase all of these losses, and a decrease in your system flow will decrease all of these losses. The extent of the change will be dependent on how much your flow rate is changing and how efficiently your plumbing system is designed in order to handle the change.

The combination of pressure head, velocity head, and friction head (and another factor I will explain later) within your system is what is giving you the 3.5psi reading. Your 3.5psi reading can be an accurate assessment of your system pressure, but there is a qualification and an adjustment that needs to be made first.

Your gauge will only tell you a valuable number if the water that is feeding the canister is coming directly from the output of the pump without going through any other items first. If your system is truly in parallel that should be the case.

Your gauge is not only measuring your system head when the pump is running, it is also measuring the static pressure of the water depth since you have a closed system. If your gauge is about 4' below the water, your gauge should be reading about 1.75psi when the pump is turned off just from the pressure of the water in the tank pressing down on the water in the pipes since there is a complete siphon. That is not "static head" though, because when the pump is turned off that tank water will be pressing down into the canister filter equally down the return line and intake line, so the net “static head” will be zero. The pump only cares about differences in pressure between the intake and output, not the water pressure within the pump itself.

Think of this. When you dive into a lake and then swim 1' under water it is easy to move your arms and legs around and you feel little pressure pushing in on your body from all sides. If you then sink down to 10' of depth you can still move your arms and legs just as easily as you could at shallower depths, but while you are doing that you will feel more water pressure pushing in against your face and the skin of your body from all directions. That pressure pushing in against you from all directions cancels itself out when it comes to movement. That is why a submarine can travel at 5 mph at 10' of depth or 100' of depth using the same amount of engine power. All the added depth wants to do is crush or implode the submarine from all directions, not slow down its' forward motion.

You have the same issue. Your pump being 4' or so below the tank when everything is set up is causing the water to push heavily outward on the pump from all directions when the system is at rest. That pressure is water that is trying to push past the pump seals and leak water out onto the floor of the house. That is why canister filters have a maximum recommended distance that they should be mounted below the tank, to keep the pressures that are trying to leak water out of the system through the seals to a minimum. Vaughn is right, assuming that you have no plumbing losses, you could have your pump 30 feet below your tank and it would still see the same system head when the system is running, but if you did that you would see about 13psi of internal pressure within the pump even when the pump is turned off. Most pump seals for canister filters couldn’t maintain a watertight seal against that much pressure and they would leak.

In the real world however, you do have more friction, pressure, and velocity head the farther your pump is below the tank, so the pump will not be able to flow as much water when those things increase. If the pump's flow decreases enough it might not be strong enough to prime itself or pull air bubbles down through the intake line and keep a complete siphon going in the system. As a bubble sinks in water, the increased water pressure compresses that bubble and the bubble becomes smaller. Water does the same thing, but the compression is almost non-existent since water is so dense to begin with. The smaller a bubble is the faster the water around it has to be traveling in the downward direction in order to keep pulling that stray bubble down inside the canister intake pipe (in order to keep the system primed). Most pumps aren't strong enough to pull bubbles down for more than a few feet at most, so that's another reason why you can’t have the canister too far below the tank.

Now for info specific to your setup. I would adjust the mazzei to exactly the flow level you desire, and also add all of the media to the system that you will eventually be using before taking your pressure reading at the canister. Any change in a single leg of a parallel system will change the flow rates and pressure drop across all of the other legs of the system. Just your canister filter getting dirty will increase your flow rate through your mazzei for example as your system finds a new balance based on the higher resistance through the canister filter. After everything is added and the system is adjusted for optimal flows through all of the elements, turn your pump off and then read the gauge. It should read about 1.75psi or so. That can be subtracted from the reading you have when everything is up and running. Now turn the system on and take another gauge reading. Subtract the reading from when the system was off and that will be your system’s total head resistance. It might sound surprising to you that your system head is so small, but that's because you have everything in parallel. If it was all plumbed in series you would be looking at something in the neighborhood of 15' of system head (even without there being any static head), but most likely you will be somewhere around 4' or so with your setup. You might be wondering why anyone would ever run everything in series with that being true. When the system is in series every drop of water runs through every system element, so there is 100% filtration for every drop of water. With parallel plumbing like you have only around 1/3 of the water that goes through the pump actually goes through the canister filter assuming that you have 3 parallel legs that are each flowing about the same amount of water. That is fine though for the levels of flow you want to be running. You are essentially using your plumbing system for simple tank circulation just as much as you are using it for filtration.

I would size the new pump to flow 1000gph at your corrected head measurement from the gauge after everything is tweaked, the static reading is subtracted, and the media is added. That will underestimate your actual flow a bit when you are all set up in order to ensure that you will still have at least 1000gph of flow even when your filter cartridges are dirty.

The main problem that I can see happening is this. When you have parallel legs like you have, there is a certain level of flow that you need through each element (like your mazzei) in order for it to even work effectively. You might find that going down to a 1000gph pump is too little system flow to get adequate water flow through all of your parallel system elements. If that happens you will then have to change some stuff to series plumbing in order to increase the flows through the individual elements, but that will increase system head and drop your pump’s flow rate, so it is a possible catch-22. It is hard to know if everything will work fine as you have it with only 1000gph of flow, because the Reeflo Dart pump you are using now is flowing more than 2x that 1000gph level right now. In order to find out if this will be an issue, try this. If you can turn your mazzei flow rate down 50% from what it is right now and still get good misting I think you will be okay, but if not I don’t think buying a new pump that can flow 1000gph will work without rearranging things a little bit. Rearranging things will change the system head so your new pump will then be mismatched for the flow level you are looking for.

Have a good one, Jeremy

Thanks alot for the replies everyone
What you have said about static head is true. However, as mentioned before - in my case I only have a 1" intake, which poses a problem for the gravity fed static pressure constant - the max that can flow through 1" through gavity in my take is around 1100-1200gph, the rest needs to be sucked with the pump - hence the whole calculation is kinda off as far as I understand it. Thanks for the advice though.
The main problem I have right now though is that my Gold dart pump (2nd pump I purchased at the same store) seems to be noisy(not vibration noise, but bearing noise it seems). I can spend the money for a Red Dragon, which in the long run almost pays for itself with the saves electricity bill(esp. around here in NJ) but its a low head pump, with only 12' head, and as most flow pumps, it is designed for a larger intake pipe than I planned for. Any idea on whether its a good idea to get one? (assuming my head is around 6-8' which it will be after pleat cartriges get dirty). Any Silent or near silent pumps out there with a decent(20') head?

Even though I have a large planted 250g discus tank, I'm relativly new to more complex plumbing, the 250 gallon is run with a couple of large anisters and an inline diy reactor, it does have an auto water change system. I am learning as I go, and its fun to do a high tech 60g cube, one that I dont need to almost do any maintanence on(hopefully). I have found out the hard way how difficult it can be to fit alot of plumbing into a very narrow box(24x24x24).

Again, thanks alot for all the advice, every bit is appreciated!

-Chris.

Ntino,


If you are feeling thrown off by the intake starvation (you think you have) I can show you the calcs to prove to you that your intake (even now) is not starved at all (providing the assumptions within my calcs can be applied to your system), and I will show you exactly how much it is actually affecting your readings now and after you switch pumps.

The point of intercept for all the calcs related to your current system (as I understand it) with the pump curve for a Reeflo Dart pump is at ~2000gph. That is what you are actually flowing when your canister gauge reads 3.5psi. Now I will show you how I achieved those calcs and your total system head ratings.

Assuming your 1” intake line is around 5’ long, you would need to have a 40” vertical drop over that 5’ pipe length in order for the 1” line to flow 2000gph by the pressure of a gravity siphon pushing water into the pipe (according to my own math and confirmed by several fluid flow calculators online).

This means that if you have at least a 40” drop between the tank water surface and the intake side of your pump you have no pump starvation occurring right now. Also, any vertical distance between the pump intake and the tank surface water greater than 40” can then be subtracted from your canister gauge reading on the output side in order to determine your total current system head.

For instance, if you actually have a 48” drop from the tank to the pump intake, you would have a pressure of 0.3psi at your pump intake when the pump is running, because 48" - 40" = 8". Convert 8" to psi = 0.3psi. Your total system head would be the full gauge reading at the canister (3.5psi) minus the 0.3psi you would have at the intake, so you would need to use 3.5psi – 0.3psi = 3.2psi for your current system head rating. That would mean that your total system head would be 3.2 x 2.3 = 7.3’. Looking at your Reeflo Dart pump flow curve, your pump flows about exactly 2000gph at 7.3’ of system head, so all the calcs fit and match perfectly in both directions. That means that if your pump intake is actually 48" below the aquarium water surface you will be flowing ~2000gph with your setup as you have it now.

The issue though, is that I thought you were talking about wanting a future pump that flows 1000gph, not ~2000gph like you have it now. Instead of 40” of drop, it only takes 10” of drop over 5’ of 1” intake pipe to flow 1000gph by gravity in a siphon setup, so all you would need to add to your 4’ of current output head (after the static pressure is subtracted from your gauge pressure when the pump is on) would be 10” more head to account for the intake sizing you have, so your total system head at 1000gph would be 4’10”. This is what I was meaning when I was saying that right now you are flowing about 2x (2000gph) what you want to be flowing with the new pump (1000gph), and that your total system head will change quite a bit when you drop the flow rate through your system (since your losses are all flow specific). At 2000gph of flow your intake is contributing to 40” of head resistance, but with only 1000gph of flow the exact same intake will only be contributing 10” of system head.

I didn’t mention the 10” difference you will have at 1000gph, because the 4’ of head you are now seeing on the output side will also drop some as well when you drop your total flow rate, and that will more than make up for that 10” of static pressure loss on the intake side. That’s why 4’ (or whatever your gauge reading is when it is all set up with the media and mazzei perfectly adjusted and after the static water pressure reading when the pump is off is subtracted) is a good total to work from for sizing a future 1000gph pump. That result already assures that you will have at least 1000gph of flow through your system even when the canister filters get dirty.

You should have no problem finding a nice pump that flows 1000gph at 4-5’ of head. A Red Dragon can do that job nicely. As I mentioned before, your biggest issue is going to be whether 1000gph is enough to feed all of your parallel components with the flow they need to filter the water, mist your CO2 adequately, etc. If not you will have to re-plumb some stuff in series in order to make it all work right with the lower system flow. Doing that will change all of your parameters, and will depend on how you do it, so it can't be calculated very successfully in advance.

Have a good one, Jeremy

P.S.- Here is one of the best and most accurate fluid flow calculators I have found online, and you can use it to verify my calcs if you want

CalcTool: Gravity-fed pipe flow calculator

2000gph = 33.3gal/min, and the roughness coefficient is between 145-150 for SCH 40 PVC pipe

Side note related to the link- For others reading this, that calculator only works for canister systems and/or gravity fed systems that have a complete siphon like Chris has. This calculator will not work for sizing or calculating flows for tank overflows to a sump, etc. that do not actually have a complete siphon. Those systems pull in air in addition to the water, and the water flow rate is also restricted by the overflow being so close to the tank water surface which completely prevents gravity from being able to push water down the pipe. Both of those things reduce the possible flow rates through the same size piping.

Thanks so much for all your help, I am learning alot.

One thing though - one of your assumptions is not correct is seems - the psi at my pump level when pump is off is at 1psi, PSI at almost the very bottom is 2 PSI(on top of the ocean clear canister, I imagine its even abit lower at the very bottom).

My problem was that I based my intake starvation calculations on post I read about somebody that has a sump, obviously this is a different case. Thanks for clearing it up for me. Are you sure you calculate from surface of tank? Psi wouldnt be the same at surface as bottom(I'm sure you know better, I just wanted to make sure I got it right).
Help me out with another question - basically, if I have this right - there should be no problem downsizing the 1 1/2 inch intake and 1 1/4 output of the dragon pump to 1" on both ends as long as I know that my total flow wont be more than say... 1800gph?

Also, as mentioned before, I have roughly 3.5 psi read on my canisters, but that is when there is no media inside, I will have more with media. My mazzei runs fine without throttling down anything else, there is a 5 psi difference, which is plenty enough for a small mazzei (the bubbles comming out are as small as dust, any finer and they would not be visible).

My main concern is basically this - I dont mind having more GPH, I can always throttle down. If I do get the red dragon - they are so efficient that even if I get a bigger one and not keep it open all the way, there isnt that much difference - largest pump is rated at 108w.
However, I was concerned with head starvation, and am now concerned with whether I need a higher head pump 3.5-4 psi is close to 5.5 psi, which is the best this or a red dragon can do, so when filters clogg, I am afraid I will have very little flow. Unfortunately I dont know of any higher head pumps that are quiet enough to not be heard with the cabinet shut.

P.S. Is it OK to have 1 90 degree elbow on the intake side of the pump? I have one and was wondering whether I need to replumb - working inside a very small stand with 1" pumbing is just difficult if you have 4 modules, a mazzei, guages, CO2 tank, ect.

Thanks again for your help.
-Chris.

I attached an image of the plumbing - this is pretty much how its giong to stay, only thing missing is a PH controller