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double your filters flow rate


r.d.m

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To summarise;

If you have your canister filter plumbed directly into the bottom of your tank, it will have NO head to deal with.

If you have your canister filter hooked into your tank, via walking sticks and such (ie. going over the edge of the tank), the head it will have to deal with will be dictated by the water level of the tank. That is, if your tank is completely filled, right to the top, to the underside of the reinforcing bar, the head will be only a centimetre or two - the height from the bottom of the reinforcing bar to the highest point your pipes go to in order to get over the edge of the tank.

In this situation, if you drop the water level in your tank, you will increase the head of the pump, and reduce your filter’s output.

If you are able to shorten the intake/outlet of the filter, you will improve the flow rate of your pump by reducing the friction caused by the water turbulence inside the tubing, AND the friction that occurs from the water in contact with the inside diameter of the tubing itself.

Craig

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My, this thread had been bubbling away since I saw it last!

Just to stir the pot a little more re these parts of the last answer...

If you have your canister filter plumbed directly into the bottom of your tank, it will have NO head to deal with.

OK I'm with you so far

If you have your canister filter hooked into your tank, via walking sticks and such (ie. going over the edge of the tank), the head it will have to deal with will be dictated by the water level of the tank.

Lost me here.

Why, isnt it still a closed system where no air can get in and hence no backflow can occur no matter how far above the water level the pipe crook is located.

That is, if your tank is completely filled, right to the top, to the underside of the reinforcing bar, the head will be only a centimetre or two - the height from the bottom of the reinforcing bar to the highest point your pipes go to in order to get over the edge of the tank.

I suppose that this is the case if you are dealing with a walking stick and a spray bar.

To illustrate my above query, hypothetically speaking if you were to use two walking sticks and drained the tank to the lowest point while keeping the ends of BOTH pipes submerged. What would be the increase in head pressure from a full tank with with the same set up (thats not to say that I can see why you would want that setup).

To my mind it should be none because the siphon is still in effect, i.e. it remains a closed system.

Cheers for the debate all

-worm-

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So hypothetically, if the intake pipe was 90cm, and the output was 30cm - is there any difference (caused by friction) than if the hoses were both 60cm?

(90 and 30 = ... wait I can do it.....a total length of 120 cm (not including the canister itself). If both pipes were 60 cm, then you have a total of 120cm - so no difference.

To confuse it a bit though, some filters have different diameter inlet and outlet pipes, but the principle is still the same.

Lost me here.

Why, isnt it still a closed system where no air can get in and hence no backflow can occur no matter how far above the water level the pipe crook is located.

As I already mentioned, get a siphon hose started into a bucket. Once started, put you finger over the outlet end, and raise it to just a bit above the level of the water in the tank where the water is coming from. Take your finger off the siphon hose, keeping the inlet end in the tank.

The water will stabilise in the outlet side of the hose, and should equal the level in the tank.

That is, gravity will cause the water to flow to this height, without the aid of a pump. If you want the water to go above this point (back into the tank), you will need a pump to flow.

To illustrate my above query, hypothetically speaking if you were to use two walking sticks and drained the tank to the lowest point while keeping the ends of BOTH pipes submerged. What would be the increase in head pressure from a full tank with with the same set up (thats not to say that I can see why you would want that setup).

To my mind it should be none because the siphon is still in effect, i.e. it remains a closed system.

If you put both ends of the siphon when filled with water into the tank (no air inside hose), the hose will stay filled, BUT, no water will move through the hose, which is what we want when we put a canister in between the inlet and outlet of the hose.

If you lower the effective height of the water in the tank, you will effectiely cause the pump to have to pump the water higher as a siphon will only work if the outlet end is lower than the inlet end.

Go test it out on a bucket.

Craig

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I may have thought of a better way to express myself.

Take the siphon hose analogy – out let end out of water – outlet end in water back in the tank.

The first ‘out of water hose’ the water will level with the water hight its inlet is in. If you want water to go beyond this point you need a pump.

The second hose’s water can’t level itself because no air can get in. But this doesn’t change the effect gravity has on the water in the hose, nor does it change the fact you need a pump to pump it past this “level” point just because you can’t see it.

Craig

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