Proper drilling

[mass]

Hi,

Is it possible to drill holes into the bottom (floor plane) of tank for water in/out used by external canister filter? Well, i know - its possible to drill anywhere, BUT if the filter are located under the tank - hidden in the stand shelf - i'm not sure if filter pump will hold all the pressure of 350 liter tank and will be able to pump the filtered water upwards, back into the tank?

I just want to hide any pipes and holes, so this maybe is a solution.

[Ira]

No, the cannister doesn't have to pump against any pressure until it's pumping it above the tank's water level.

[mass]

Then only possible solution is to run a hose trough the tanks floor till the top of the water level?

Or even those ~70 cm of hose height will make too much pressure?

___

*Not "dont get" but "dont know" - thats why I'm asking questions.

[spooky]

Ira's point is that the canister only has to pump against the *difference* in pressure between its input and its output.

If you have two hoses going up to an equal height then the water in the input hose pushes down (and helps the pump) by the same amount that the water in the outlet hose is pushing back. So it all cancels out.

In fact, as long as the inlet and outlet are below the water line, they don't have to be the same height since you have to account for the tank water above them as well and the real water-column height is then taken from the top of the tank, which is conveniently level.

Looping the hose over the side of the tank is also self-cancelling, the only time you get any pressure difference is if you put the outlet above the tank, but since the worst I have ever seen

This discussion doesn't allow for friction in the hoses or anything like that, but these effects are usually negligible. You also have to worry about the pressure at the seals, but the pumps are designed for this sort of use and once again you can generally ignore the problem.

As for you original question about drilling holes: it has been done, usually by people installing a "stand-pipe". The salt-water people seem to do it a lot, but I don't know any of the details.

[suphew]

YEah this is possible but not recommended because if anything goes wrong (like not putting the seal together correctly after cleaning your filter) you will drain the whole tank. Have a look at the salt water forums, check out the stand pipes, this is most popular way to do things.

I do have a closed loop on my tank which is basically a hole in the bottom that feeds directly into a pump then back into the tank via two other holes. I'm only happy doing this because I have a high quality parts, eheim pump, hansen flanges and taps, glued pressure pipes for the plumbing. And lastly a sump that sits under the whole lot. I couldnt sleep at night if I was using a external cannister files to do this.

[Interfecus]

mass - I'm not sure whether you're talking about the pressure the pump is pumping against or the pressure the seals can withstand.

If you're talking about pumping, the force to lift water upwards is provided by the pressure in the downward pipe as already mentioned by others. Only the difference between inlet and outlet height (or the level of the water they may be immersed in) contributes to the resistance to pumping. The same is true for pipes going up over the rim of the tank (unless they reach a height of more than 10 metres above the water surface, at which point there is a vacuum at the peak which prevents the passage of water ).

If you're referring to the pressure the seals can take, see whether they have a pressure rating. Take the distance from the bottom of the canister to the water level of the tank in metres and multiply it by 10. This will be the pressure on the seals in kilopascals. Make sure the seal is rated at at least half as much again as this for safety.