siphon stops before time

[ofer cohen]

HI everybody ' I'm new to this forum and to the aquaponic world

I just finished building my first system ' it is really small , the fish tank is about 40 - 50 liters and the growing bed is about 15 liters, I think that I might split the tube in two and add another 15 liter tank as a growing bed .

I have a siphon problem - the water comes up to the top and than the siphon breaks and the water level is droping faster than the tank is filled with new water , so far I think its good right? but than the siphon stops draining the water befor time - it leaves about 1/3 of the tank filled with water , for some reason air is coming up the pipe and stoping the vacum - this is what I think is happening . so why is that? and how can I fix it ?

the picture that i uploaded is old one , now there are 3 plants in the growing bed - 2 kinds of beans and luiza and there are 13 golden fishes in the tank that now is filled with clearer water .

thanx alot in advence !!!

[David Waite]

Ofer I think when your tank is full the guard has plenty of holes to supply water to the siphon. As your siphon drains it has less holes in the bottom half of the pipe and cant supply all the water the siphon needs hence the premature siphon break. Cut more slits or drill more holes in the bottom half of your guard and see what happens. The second think I would do is slow down the siphon by turning the siphon up a little on the bottom. Try those..................D

[ofer cohen]

mmm ok , that makes sense , actualy I have holes only in the bottom of my guard , and I thought that air is coming in when the water level gets to them ,  you say that I should try make more holes or make the ones that I have bigger?

today I came back from work and the siphon didnt work - so I pushed the siphon to the bottem and it worked again so I dont think that the second option would work .....

thnks alot !

[David Waite]

Ofer if you only have holes in the bottom of your guard I would lean to the first problem of putting more holes in the guard. As water pressure drops or water level drops the siphon has to pull harder and having restriction or to few holes will create a premature sucking and maybe in your case siphon break.

[ofer cohen]

OK , I think I got it I will try and report . thanx David !
David Waite said:

Ofer if you only have holes in the bottom of your guard I would lean to the first problem of putting more holes in the guard. As water pressure drops or water level drops the siphon has to pull harder and having restriction or to few holes will create a premature sucking and maybe in your case siphon break.

[TCLynx]

Premature siphon break is usually from the water not flowing through the gravel guard or the media itself quick enough for the siphon so it sucks the water down low in the gravel guard really fast and then manages to get a gulp of air and cut out while most of the bed is actually still quite full of water.

[ofer cohen]

I'm not sure I understood it , maybe tell me how can I fix it if thats the problem

[TCLynx]

If the problem is the siphon is too big/fast for the flow rate through the gravel guard you can make the gravel guard allow more flow (cut more slits/holes in it especially lower down.)

 

If the problem is the siphon is to big/fast for the flow rate through the gravel itself (as in the gravel is too small/compact to let the water flow through it fast enough) you would either need bigger gravel or you might do better to make a smaller siphon.