Ordered a new canister filter.

The distance from where the canister sits to the tank top is just under 49" for my setup. Subtract 12" or so to where the pump discharges. It's flow rate definitely seems better than the Sunsun HW-302 it replaced, but all is new yet. It probably would turn over the volume of a 55gal 3x per hour.
 
TwoTankAmin said:
I spent some time looking for the head graph for Eheim canisters. I can find the max. head number but not the chart. I may exust on the Eheim German language site but I am not sure what term they use. However, here is an interestimg tthread on this subject from Nov. 2010 on theplanted tank.net: https://www.plantedtank.net/forums/...im-flow-2215-2217-tested-terrible-so-far.html
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So you're saying the flow increases significantly if you raise the canister a bit? (I don't mean from 100 to 101,2 gph or something like that) That's interesting I've never considered that.
Did you do any before/after tests with your raised canisters?
 
the loach said:
So you're saying the flow increases significantly if you raise the canister a bit? (I don't mean from 100 to 101,2 gph or something like that) That's interesting I've never considered that.
Did you do any before/after tests with your raised canisters?
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There's no way to give an across the board number for that. Too many variables at play. Raising the canister in relation to the water level will also eventually have a negative effect on flow. If the suction side has to work harder to get water in, the output flow will decrease. You'd have to find the sweet spot based on your specific setup.

I'm really not sure why this would be a concern anyway given most of us run canisters so that we can keep them out of sight. I'd also not want the hoses so short that I don't have any options for canister placement. AKA- short hose syndrome (all too familiar) I just made that up.

I am familiar with fluid dynamics. ~25yrs ago I worked in the test lab for a pump manufacturer that made pumps for the Navy and commercial marine industry. We had massive water tanks that we could heat to the boiling point and would custom build the piping arrangements as needed for the tests. Also had huge oil sumps to test lube oil pumps. It was kind of neat.
 
As far as i know there is no suction per se. Gravity feeds the input side as long as water is leaving because it is pumped back to the tank. A canister functions the same way as a sump does. The difference is the canister is sealed and the sump is not.

All pumps have head curves, the higher the water must be lifted, the slower it moves. Ultimately one hits the max. head and no water will come out of the return side. For the Eheim 2215 that height appears to be 5'11". I still cannot find a head curve for the Eheim canisters. I can find them for their pumps.

I never did tests. However, if you look at head curves for pumps and filters whose manufacturer publishes them, you will see head height matters. I tend to raise my canisters by about 12 inches which ends them up about 44 inches from the tank rim. On my 150 that distance is more like 47/48 inches.

The difficulty with this discussion is that not only does head height affect flow rate, but so does the hose length and the specific media used as well as if one uses a spraybar or another type of output.
 
It took me some time, but i did find some head info re Eheim. it will provide some idea of what head does to diminish flow. The below chart if for their 1260 return which has a max. rated output of 625 gph at 0 head height.
image-jpg.209835


At a head height of 4 ft. the flow looks to be about 435 gph which is a drop of about 200 gph or 50 gph/foot. Since at 12'1' is the max head, that would work out to 635 gph/12.083 ft., or about 52.2 gph for each foot the head is raised. That is about a loss of 12% of capacity for each foot the head height is raised. Bear in mind that head height flow rates are a function of the total water weight being lifted (i.e. all the water inside the return hose until it starts to come out). That weight increases with height, but also if the diameter of the return hose is widened.

There is one other factor to bear in mind here. The potential flow rate of the intake side of any filter must be at least as great as return flow rate for that filter. If the return rate is higher, the filter will soon empty itself.

Many years ago in a long defunct fish chat I was taught about pumps by a gent who spent his life working with the really big ones. Hge pums like those in electric power plants or other extremely high flow applications. He explained that flow should always be controlled from the output side, never from the intake side. If the output side of a pump is above the maximum head, the pump will run fine for a long time without any water coming out of the output side. On the other hand if the intake side is impeded and the output side maintains the same output flow, the pump will destroy itself in short order.
 
Thanks for looking that up. So this diagram does take into account the hose length? Head height at 0 means at water level?
It does look like it will pay off to just raise the canisters a foot or so (I don't think many folks have them sitting next, or behind the tank at tank level) I'll be cutting some wood blocks.
 
Very cool that Eheim actually publishes head curves for some of their products. You'd have to beg and plead to get that info from other manufacturers.. If they even had it available.

In terms of the pump lesson, again, very cool. I dunno if that was directed at me or the general population, but like said above, I'm intimately familiar. I worked in the pump industry in R&D for years and still do in a roundabout way.
 
for some reason I never bought into the SunSun filters. Matter of fact I'm pretty much strictly Eheim. They have proven themselves with performance, and durability.
 
The pump details were for general consumption.

0 head means the water is not being raised from the water level from where it is being pumped. This diagram from a reefkeeping.com article on Aquarium Water Pumps explains it perfectly:

image009.gif

from http://www.reefkeeping.com/issues/2002-05/rn/feature/index.php

More companies publish head curves. When I was looking to buy my pumps (used for emptying some tanks and for refilling all of them) I needed head info. I have tanks where the top rim is at least 5 ft. above the lower level of the stand. I have to pump refilling water to that height. I was less concerned with how fast a pump worked with lower tanks rims. That Eheim pumps curve would turn the 635 gph max flow rate to be more like 350 gph. My 150 holds about 125 gals. I change 65. At 635 gph that takes about 6.5 minutes. At 350 gph that becomes 11.25 minutes. My main refill pump has a max flow rate of 1020 gph.
 
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smitty said:
for some reason I never bought into the SunSun filters. Matter of fact I'm pretty much strictly Eheim. They have proven themselves with performance, and durability.
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I get that. Thing is.. and I'm sure you know this, even Eheim's quality is sketchy now. I am not impressed by the materials quality of my new Eheim classic 350 / 2215 for what it cost and a few eheim replacement parts will exceed the cost of an entire new Sunsun unit.

I am not sure yet that I would buy another Eheim. I do like the massive amount of bio media they come with and their unique old school design. I would however buy another Sunsun in a heartbeat.

If I wanted to pay up for what I think is a quality canister these days, I'd by an Oase biomaster. That pre-filter is just so sweet. Plus if you go biomaster "thermo", it's got a heater built into it.
 
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