Tips: Do You Need A Sump...?

[vaypourus]

I should modify my statement a little concerning head loss:

*IF* the water is discharged from the canister at the water level of the tank or below, you are not going to see a true "head loss" as the water level will remain even on both sides of the intake and exhaust sides of the system. This is generally not the way people seem to setup the exhaust however; any spraybar or exit used above the water level will result in head loss.

You are going to see additional loss on some canister filters as the intake tubes are not big enough to allow the flow from gravity alone to equal the flow of the pump. This may or may not be accounted for by the manufacturers.

For example: going back to the FX5. The intake hose is 25mm, which is just under an inch in OD. Even if we round the ID to an inch even, we see that flow through this size tube is roughly 600 GPH. The FX5 is rated at 965 GPH, which means that the pump in the canister is doing additional work to suck the water through the intake hose at a higher pressure (to get additional flow through the tube). This of course means that the pump is experiencing loss. I don't think this qualifies as head loss, but is loss none the less.

The bottom line here is that it really depends on the manufacturer and how they measure the flow in the filter. Due to the lower true GPH I've seen on most canister filters, I would assume that many manufacturers rate the pumps themselves and not the filter as a whole. This is of course an assumption, but explains why even an empty canister with no media does not live up to the rated GPH.

You don't see this with a sump....since it is an open system, gravity can only pull so much water through the intake/bulkheads. The only work the pump does is pushing the water back into the tank. This is why drilled tanks do hit a wall with flow; the overflows can only drain so much water due to gravity.

 

[vfc]

Yes but the downward flow from the tank into the sump does not help push the water back into the tank like a canister's close system.

Plus a sump would have more tube friction loss due to the higher GPH.

 

[vfc]

We should be getting more replies to this thread now that the men's hockey game is over.

 

[vfc]

Keep in mine that the canister hoses fit OVER the pump connectors. So the ID of the hoses is larger than the ID of the pump hosing.

 

[vaypourus]

Yes but the downward flow from the tank into the sump does not help push the water back into the tank like a canister's close system.

I didn't say that gravity helps the pump in a sump.

The downward flow in a canister doesn't push the water back into the tank. Gravity will keep the water level in the intake and exhaust in equilibrium. The pump in the canister does the work; gravity does not add to the GPH in a canister.

 

[vaypourus]

Keep in mine that the canister hoses fit OVER the pump connectors. So the ID of the hoses is larger than the ID of the pump hosing.

This is true, which results in even less flow through the canister.

 

[vfc]

The two points I am making are: 1 - there is no head-loss in a canister due to gravity; the downward force is equal to the upward force, 2 - a canister's pump housing ID is smaller than the ID of the hose, so there is very little head loss due to hose friction. So if a canister is rated at 900GPH, given a clean filter, you get close to 900GPH flow.

The same can't be said for a sump. A sump has to overcome head loss due to both gravity and higher hose friction due to higher GPH.

 

[Pharaoh]

But are the fish better off if you had a larger tank with a couple canister filters?

For example; what is better: a 125G aquarium with a 75G sump or a 200G aquarium with canister filtration? I think the same group of fish would be "happier" in the larger tank.

....and before someone says a 200G with a 75G sump is better; let's just say, due to space and noise limitations, these two combinations are the only choices.

I understand the benefits you listed are valid but it's not enough of an advantage over a couple canisters with an in-line heater.

The biggest sump drawback for me is the noise.

The comparison listed above makes no sense. To compare apples to apples you would need to maintain the same basic components. So, offering two different size tanks make this argument irrelevant. One 125 with a sump and one 125 with a canister filter.... both will get the job done. The only way to know which one would be better is to know the exact specifics of each part of the sump. This is not something that can just be broadly defined.

We could go on all day long as to which is better canisters, sumps or wet dry systems. It all boils down to budget, time, effort and personal preference.

Sumps can be very efficient in comparison to running multiple canister filters. If you have 5 tanks, do you run one sump or five canister filters? Sumps are known to be a bit easier to maintain. I have both and I will tell you that sumps can reduce the amount of time spent changing mechanical media and with it, it is generally a lot easier to do so. People also love to place their heaters and misc items into the sump to get them out of the tank.

 

[vaypourus]

The two points I am making are that there is no head-loss in a canister due to gravity; the downward force is equal to the upward force. Also a canister's pump housing ID is smaller than the ID of the hose, so there is very little head loss due to friction. So if a canister is rated at 900GPH, given a clean filter, you get close to 900GPH flow.

The same can't be said for a sump.

As I already said, this is only true if the exit of the canister is at the water level or below. If the discharge is above the water level, you will experience head loss as you are pushing the water above the water line.

Additionally, I think it is an accepted fact that you will not see anywhere close to the actual GPH that a manufacturer says you will. In my experience you will see 50% to 70% of what they rate a canister; there are plenty of other articles that confirm this. Clean or not, you aren't going to see 900 GPH on a canister rated at 900 GPH.

 

[fox3]

The holes along the sides of a overflow are draining only a small percentage of the flow; the majority comes from the surface.

Head loss from tube friction is far less than from gravity. Canisters do not have head loss from gravity; sumps do.

You are entitled to your own opinions not your own facts. I have three tanks now operating with megaflows so I can speak from experience. You would not believe how much flows thru those slits on the bottom and middle of the weir. I can not say that I have measured the flow directly but can tell you that when I vigorously stir the substrate more is pulled thru those slits than what goes over the top. Clears an atrosiously turbid stirred tank to clear in 15 minutes.

About head loss a can does not experience the same degree of loss as a open loop system but a closed loop system degrades over time requiring maintenance or lower flow will be realised. Thing is I get 1800 gph outta a mag24 after loss. Whatcha gettin outta that can?