Joshlikesfish Posted August 21, 2010 Report Share Posted August 21, 2010 I don't like my EHIEM 2213. Then again, the previous owner had been running it besides the tank without a decent head height. Replaced the hoses to give it a decent head height(the ones he had were very short) and its just as useless. Quote Link to comment Share on other sites More sharing options...
Ira Posted August 21, 2010 Report Share Posted August 21, 2010 I don't like my EHIEM 2213. Then again, the previous owner had been running it besides the tank without a decent head height. Replaced the hoses to give it a decent head height(the ones he had were very short) and its just as useless. You can't change head height unless raise the outlet above the water. And any head height at all makes a lot of splashing and decreases flow. Now, if you're talking about the physical distance of the cannister below water level, that's not head height. But I can't see why that would make a difference. The extra water pressure might minimise cavitation a little but that's nowhere near an issue with these kind of pumps. Quote Link to comment Share on other sites More sharing options...
Joshlikesfish Posted August 21, 2010 Report Share Posted August 21, 2010 You can't change head height unless raise the outlet above the water. And any head height at all makes a lot of splashing and decreases flow. Now, if you're talking about the physical distance of the cannister below water level, that's not head height. But I can't see why that would make a difference. The extra water pressure might minimise cavitation a little but that's nowhere near an issue with these kind of pumps. For some reason i thought head height was how much it could travel upwards. My bad! Yeah i lowered it even more. P44 said it was gravity powered or something and i had been ruining it by running besides the tank Quote Link to comment Share on other sites More sharing options...
David R Posted August 21, 2010 Report Share Posted August 21, 2010 For some reason i thought head height was how much it could travel upwards. It is, but with a canister filter if the intake and return are at the same height (as they are when they go over the back of the tank side by side) then you have a zero head height, even if the canister is a metre below the tank. For the record I currently run two aqua ones and two via aquas, they all do their intended job and were good value for money as cheap second hand items. But money aside, there is no doubt in my mind the Eheims are a better product. Quote Link to comment Share on other sites More sharing options...
Joshlikesfish Posted August 21, 2010 Report Share Posted August 21, 2010 Thanks for clearing that up David Quote Link to comment Share on other sites More sharing options...
Ira Posted August 21, 2010 Report Share Posted August 21, 2010 For some reason i thought head height was how much it could travel upwards. My bad! Yeah i lowered it even more. P44 said it was gravity powered or something and i had been ruining it by running besides the tank It how high it can pump the water upwards above the SOURCE water level. It's the difference in heights between the intake water source(the top of the water in your tank) and the outlet water. So if your spray bar is under the water your head height is 0. That's because there is no height difference between the surface of the water in your fishtank and the surface of the water in your fish tank. The weight of water pushing down the intake matches the water pushing down the outlet. So there is no weight of water that the pump has to lift. If you raise the spray bar a foot above the water then it's the difference between the surface and the outlet. The pump has to lift the water that extra amount requiring more energy and decreasing flow. If you put the spray bar outside the tank and below the water leven then it's operating at a negative head. You have more pressure pushing down the intake than you have the weight of the water in outlet pushing down. So you have water pouring out, that's what makes a siphon work. Quote Link to comment Share on other sites More sharing options...
kiwiplymouth Posted August 21, 2010 Report Share Posted August 21, 2010 I beg to differ Ira. Head height is the difference between the intake and the outlet. So if your tank is 700 high and your intake is at the bottom of the tank and your outlet is 100 below the top of the tank, then you have a head of 600 Quote Link to comment Share on other sites More sharing options...
Ira Posted August 21, 2010 Report Share Posted August 21, 2010 I beg to differ Ira. Head height is the difference between the intake and the outlet. So if your tank is 700 high and your intake is at the bottom of the tank and your outlet is 100 below the top of the tank, then you have a head of 600 Lol, no. The inlet and outlet location is irrelevant, it's the water levels that mater. Quote Link to comment Share on other sites More sharing options...
spoon Posted August 21, 2010 Report Share Posted August 21, 2010 that whole idea is interesting and i never understood it till now . but of course the longer the hose the more resistance you will get so the lower the flow right? Quote Link to comment Share on other sites More sharing options...
kiwiplymouth Posted August 21, 2010 Report Share Posted August 21, 2010 Lol, no. The inlet and outlet location is irrelevant, it's the water levels that mater. So if in the above scenario my outlet was 1mm below the surface, I have zero head. If i raise my outlet 1mm above the surface I then have 600 head Quote Link to comment Share on other sites More sharing options...
Ira Posted August 21, 2010 Report Share Posted August 21, 2010 So if in the above scenario my outlet was 1mm below the surface, I have zero head. If i raise my outlet 1mm above the surface I then have 600 head No, you have 1mm head. Because your outlet is 1mm above the surface. Quote Link to comment Share on other sites More sharing options...
kiwiplymouth Posted August 21, 2010 Report Share Posted August 21, 2010 So when both the intake and outlet are below the surface, the differences in water pressure between the two have no influence on head ?? Quote Link to comment Share on other sites More sharing options...
Ira Posted August 21, 2010 Report Share Posted August 21, 2010 So when both the intake and outlet are below the surface, the differences in water pressure between the two have no influence on head ?? No, it doesn't. Quote Link to comment Share on other sites More sharing options...
livingart Posted August 21, 2010 Report Share Posted August 21, 2010 all down to the pump trying to push water up against gravity pressure higher outlet more pressure Quote Link to comment Share on other sites More sharing options...
phoenix44 Posted August 21, 2010 Report Share Posted August 21, 2010 so what happens if your intake is at the bottom of the tank (say 45 cm or so) and the outlet is at the top? Quote Link to comment Share on other sites More sharing options...
livingart Posted August 21, 2010 Report Share Posted August 21, 2010 the water flows up the pipe by itself ie: water level then the pump takes over just like syphoning tank water it wil flow downhill but as you lift end of pipe it will only floww when below level of tankwater after that to lift water higher than tank level requires a pump hence head height is any thing above level of water in tank Quote Link to comment Share on other sites More sharing options...
phoenix44 Posted August 21, 2010 Report Share Posted August 21, 2010 So the pump is only used for the last 45cm or so? Apart from the fact that this works in concept because of the whole gravity and equilibrium and all... but isn't accurate as far as our cannisters are concerned because the pump is constantly on and does physically push water up on its own irrespective of where the inlet is. Quote Link to comment Share on other sites More sharing options...
livingart Posted August 21, 2010 Report Share Posted August 21, 2010 and gravity is always present and all still relavent to hydraulic pressure to lift that water Quote Link to comment Share on other sites More sharing options...
Joshlikesfish Posted August 21, 2010 Report Share Posted August 21, 2010 and gravity is always present Hey hey hey... Remember gravity is only a theory :lol: :lol: :lol: Quote Link to comment Share on other sites More sharing options...
phoenix44 Posted August 21, 2010 Report Share Posted August 21, 2010 I have a couple of theories myself..... :-? Quote Link to comment Share on other sites More sharing options...
David R Posted August 21, 2010 Report Share Posted August 21, 2010 so what happens if your intake is at the bottom of the tank (say 45 cm or so) and the outlet is at the top? If you put a straw in your tank does the water fill up the straw? Quote Link to comment Share on other sites More sharing options...
phoenix44 Posted August 21, 2010 Report Share Posted August 21, 2010 yeah, that's exactly what I meant... Quote Link to comment Share on other sites More sharing options...
kiwiplymouth Posted August 21, 2010 Report Share Posted August 21, 2010 If you put a straw in your tank does the water fill up the straw? Not if you put your finger over the top of the straw and create a pressurised system Quote Link to comment Share on other sites More sharing options...
livingart Posted August 21, 2010 Report Share Posted August 21, 2010 closed not loop Quote Link to comment Share on other sites More sharing options...
David R Posted August 21, 2010 Report Share Posted August 21, 2010 Not if you put your finger over the top of the straw and create a pressurised system If you do that to your canister its not going to flow very well!! Stick your siphon hose 2cm into the water and suck on the end, then stick it all the way to the bottom and suck on it and see if there is a difference. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.