Canisters and head height

[Jchillin]

Awww...you just ruined a perfectly good experiment and destroyed my entire weekend czcz . I was really looking forward to holding a container to catch outflowing water in one hand while looking at a timer in the other.

Good choice in going with the fluval. As mentioned before, you control the horizontal, you control the vertical (wait a minute...that's from the "Outer Limits")..LOL. If you need help during set up...just drop a line.

 

[TomK2]

Ah, another good point about the true value of head height. The space between the intake and output nozzle is 16 inches. Thus, the head is 16 inches, not the distance from the top of the filter to the top of the output nozzle. Very obvious. Easy to forget. So the entire flow rate becomes the function of the small head height which will probably be nearly the same in all tanks, and the diameter, cleanliness, kinkiness, and length of the tubes. Must be why fluval uses the ribbed tubing, to prevetn kinks and loss of flow. I have added sections of vinyl tubing, that I am sure have some narrower spots to reduce flow, in addition to the added length. It would seem that I was wise to have set up two of them. 6x measured turnover and the water looks great.

 

[TomK2]

Awww...you just ruined a perfectly good experiment and destroyed my entire weekend czcz . I was really looking forward to holding a container to catch outflowing water in one hand while looking at a timer in the other.

so do it anyway! find out what your REAL filtration rate is. The you can throw around numbers and figures with authority, compared to those who just guess.

 

[mattrox]

I just did an experiment......

Aim: To find out what height the filter actually has to pump against gravity.

Materials: one 4ftX2ftx1.5ft tank on stand. (pics in gallery), 1 length of garden hose. Large cooler to collect spilled water.

Method: One end of the garden hose was placed in the tank about 1" from the bottom. A syphon was created. When the water started to flow the hose was raised until the syphon ceased and flow stopped. The hose was lowered until the syphon restarted.

This procedure was repeated with the end of the hose about 4" from the surface of the water at the top of the tank.

Results: Observations- Each time the water flow stopped/restarted at exactly the water level of the tank.

Conclusions: 1. The head height is zero (for a canister filter) if the filter outlet is at the surface of the tank. This means the pump is only working against frictional forces within the filter itself.
2. The height of the filter intake in the tank DOES NOT matter with respect to head height.

 

[Guest]

Wouldn't things like media choice, cleanliness of filter (impeller, media, and hoses), and other attachments (i.e. a UV) be more of an issue than head height anyway when it comes to lowering gph?

 

[mattrox]

GPH and head height are real issues in a sump system. The pump actually has to work against gravity and gravity sucks....downwards..LOL

All those things you mention, Tony, are the ONLY factors affecting gph in a sealed canister system. I'd be willing to put money on it.

Ok not actual money, but I think the experimet shows that in the general canister setup, the most head height anyone would realistically have is 0.25" -0.5" if the spraybar was above the water surface. If I can be convinced otherwise......... I'd happily wager some kudos on it.

 

[Jchillin]

Well, now that my canister is clean (did it yesterday sans the experiement) I can easily accomplish this this weekend. Right now, I have 3 compartments filled with bio and 1 with additional foam.

Should be interesting. Especially now that mattrox is happily offering kudos.

 

[TomK2]

I just did an experiment......

Aim: To find out what height the filter actually has to pump against gravity.

But of course! Think of it, water always seeks its own level. In a closed system attached to the tank, the water in any plumbing will be at the same level as the tank. I have installed plumbing to do water changes, and when off, the water in the out pipes stops at tank level. When you have a siphon system, it doesn't siphon faster when you put the hose further in the tank, only when you lower the hose that is not in the tank. Obvious, but easy to forget.

so canister flow is dependent on the resistance of the tubing and whats in the filter. That means my set up is not terribly efficient (flow wise) since I am at two thirds max capacity. If I used larger hose, or shorter hose, or cleaner hose, or less stuff in the canister baskets, or cleaner stuff in the baskets, I could improve it. Or I can leave it alone and be happy with a well running tank. 8)

 

[hashbaz]

Thank you Mattrox for putting the head height question to rest. I tried to say basically the same thing earlier - But I did not come across very forcefully. 8)

 

[mattrox]

Remeber, you want a balance between flow and flitration...

Not enough media means high flow low filtration. Too much media means low flow and a high filtration...but not MAX. filtration because slower flow means the bacteria have the potential to eat all the ammonia/nitrite and use all the oxygen before the water fully passes through the filter, meaning you don't have the highest bacterial crop possible.

So you need a good flow through lots of surface area/media. To get a better flow using the minimum length of pipe and regular cleaning of pipes/sponges and changing gunky floss is the way to achieve this, rather then less filter media.

 

[Jchillin]

All right...the results are in:

Fluval 404 Canister - MSGPH (Manufacturer's Suggested GPH) = 340 per hour

Actual results:

Based on head height of 49" and full media baskets = 278GPH.

Process: Filled 2.5 cup measuring cup for one minute.

This is very close to the manufacturers suggested rate. I assume that without the additional floss, the results would be even better.

 

[TomK2]

Not bad. That is actually better than what Fluval states. The pump is rated for 340 GPH, but Fluval states the filter flow 225 GPH. I wonder if the the pump being rated at 340, and filter flow at 225 is why people think that there is bypass in the filter.

Is it bypass, or is it just that flow goes down when the baskets are in actual use?

 

[Guest]

Tom, do you really have two 404s running in your 55 gallon tank or am I reading that wrong?

 

[TomK2]

Tom, do you really have two 404s running in your 55 gallon tank or am I reading that wrong?

yep. I have about 3ft extra tubing on them, put them in the utility room behind the tank rather than under the tank. On the fancy goldfish tank I have only one with a spray bar mounted vertically to reduce the currents.

I like them, especially for the $89 price I got them for.

 

[Guest]

Tom, do you really have two 404s running in your 55 gallon tank or am I reading that wrong?

yep. I have about 3ft extra tubing on them, put them in the utility room behind the tank rather than under the tank. On the fancy goldfish tank I have only one with a spray bar mounted vertically to reduce the currents.

I like them, especially for the $89 price I got them for.

Did you find that one was just not getting the job done for you or do you just like to overfilter? I agree with you on the Fluvals, they are great filters, but I have one 304 on my 55g and I feel like its filtered perfectly.

 

[TomK2]

In a previous incarnation, my tank had a fluval and a magnum. It didn't get regular, nice water changes, and having two filters eased my guilt for irregular maintenance. Since then, I just always have run two filters on it. I like the idea of backup if one fails, and I can service one and leave the other undisturbed. I like having current from both ends of a 4 foot tank. In a nutshell, I am just an over-filterer. The same size tank with goldfish and one fluval has exactly the same water paremeters and appearance. One Fluval 404 is enough for a 55.

If your water seems adequately mechanically filtered, and there is no ammonia or nitrite, and the filter doesn't seem to clog up to frequently, then you are doing fine with a 304. After all, biologic filtrations is the number one concern, and water clarity is second. Gallons Per Hour is meaningless if the goals are being met. I went with two 404's instead of 304's because the price difference wasn't all that great.