sihponing big tanks

[LukeR 0]

i dont know if this has been covered 
i have a big tank and i want to see what people use to do wateer changers i use a house but it feels like there you be a quicker way with using pvp pipe or some thing like that thank you 

[lgw 68]

A bigger diameter hose. I think mine is 25 or 32mm from bunnings, drains my tanks in no time.

Either that or attach a pump to your existing hose, i vote the first option.

[MFF 24]

Also - if the exit point of the hose is significantly lower than the (descending) water level in the tank, it will also go faster.   A siphon is sucked through proportional to the height difference between inflow and outflow.  Doesn't matter how high the hose reaches in between - although this will have an impact on how easy/difficult it is to get the siphon started.

What's a "big tank" for you?  My tanks are 600 L, and they drain by 30% (the size of my water changes) in about 12 minutes using a pretty small diameter hose.  This gives me time to suction the gravel/sand as well - too fast, and you can't clean the surface of the substrate.

[aquaholic99 590]

Doubling the pipe/hose diameter will quadruple the flow which is good for draining and filling.

On bigger hoses (swim pool hose or bigger) it can be hard to start the siphon by mouth so add a tap at end to maintain the prime between use. Alternatively submerge the whole hose and seal the exit end with a plastic bag until you want to start the siphon. This is especially good for 100mm PVC drainage pipe siphon. 

If you have multiple tanks to drain, make up some U bends in PVC pipe  that only go down to the level you want to empty without having to stay there. So several simultaneous drains at once. You can fill the same way but use a water level alarm. (And remove any carpet - switch to marine carpet).