overflow pipe

[bobiegoh]

yo bro,

I have designed and ran an overflow pvc pipe based on the designed i copied from this forum. Thanks to those bros contributions. The only problem I have is can't auto restart when power cut off. So, I made changes to the in water pipe portion based on another design copied from http://www.saltwaterfish.com/vb/showthread.php?p=2480264 (pardon me for putting the url here). The problem still exists. That is overflow does not auto restart when air get into the inlet.

The only thing i did not install in my design was the inner airline in the pipe which I do not understand how it works.

Please let me know how can i over come this. Need advise here. Thanks.

I desperately need expertise here.....

[bobiegoh]

yo bro,

I have designed and ran an overflow pvc pipe based on the designed i copied from this forum. Thanks to those bros contributions. The only problem I have is can't auto restart when power cut off. So, I made changes to the in water pipe portion based on another design copied from http://www.saltwaterfish.com/vb/showthread.php?p=2480264 (pardon me for putting the url here). The problem still exists. That is overflow does not auto restart when air get into the inlet.

The only thing i did not install in my design was the inner airline in the pipe which I do not understand how it works.

Please let me know how can i over come this. Need advise here. Thanks.

I desperately need expertise here.....

This is my design.

[Morpheous]

Hi Bro,

Your design will not restart as the siphon will break at the level of your pipe in your tank.

I have add additional items required in your picture. You can also include netting as seen in the bottom right of the picture to prevent small fish being sucked down to your sump. Good Luck!

Overflow.bmp

[bobiegoh]

bro, thanks for your reply. Init my design is exact like yours, having an 2" outer pipe in water (my overflow pipe is 1") with many drilled holes and open mouth. However, the water can't be suck up if my inner pipe in the 2" is long extended to the length as per your diagram. I don know what is the reason. Thereafter, I make the inner pipe shorter and closer to the mouth of the outer 2" pipe, then the siphon can began, but the siphon break when the water level fell below the 2" pipe mouth.

I need expertise advise.... help....

[Morpheous]

Bro, lengthen the "U" portion. You initial could not start cause the suction pipe is of the same level as the "U" portion. There must be height difference else the siphon will not start. The logic is the same as filling a hose with water, put one end in the tank, and the other to a pail. Water starts running only when the pail end of the hose is lower than the one in the tank.The greater the difference, the suction gets stronger.

[bobiegoh]

bro, is it the magic fall on the first U portion (The reverse U. There are 3 U)? Based on what your explanation, I extend the U reservoir portion, which make it longer. Is that Ok?

Why is that when the suck in pipe in the 2" get lengthen, it can't suck the water. And when I shorten it nearly to the surface of the water, it is ok. See my revised diagram. Is this workable?

[Morpheous]

Why is that when the suck in pipe in the 2" get lengthen, it can't suck the water. And when I shorten it nearly to the surface of the water, it is ok. See my revised diagram. Is this workable?

Take a hose, fill with water(thumbs in both end), put one in the aquarium, and the other to a pail. If both end are at same level, the siphon won't start.

If you lower the pail end, u will find that siphon starts and it gets faster flow rate is faster as you lower it even more. You are actually replicating this.

bro, is it the magic fall on the first U portion (The reverse U. There are 3 U)? Based on what your explanation, I extend the U reservoir portion, which make it longer. Is that Ok?

Yup, the "U" portion determines whether the siphon will break or not. Based on your design, because of the long length of the tube after the "U" portion, it slows down the flow rate tremendously (Needs a lot of pressure to push the water up the pipe). Therefore, the water pressure will either be not enough or it is too little. The main tank water level will need to rise tremendously to match your pump flowrate, resulting in a overflow.

The design is only a graphical representation, but the actual design requires a lot of trail and error, and there should be significant difference in the length of the left tube of the "U" portion compared to the right and looked something like below. After the design is successful, do use PVC glue to seal the joints.

In my opinion, the valve is not required.

[bobiegoh]

bro, thanks for your reply. This AM, I did some tests and found that the main problem is when the water fell below the 2" outer pipe mouth, the inner 1" pipe continue to suck-in water within the 2" pipe until air escape and siphon break. Attached is the diagram explanation. The red portion is the empty space where siphon break and air escape.

However, If i have the flexi hose submerge in the water, the suction immediately stop when the water level fell below the 2" pipe mouth as the air cannot escape from from both end of the pipe. In reality, this is not possible as the flexi hose is always sit on the filter wool on a dry area.

How can i overcome this bro? Help your great help. It will be glad if I can give you a ring at your mobile for detail explanation. My mobile no is 96664836. Thanks.

[Morpheous]

I could not explain why the siphon will not break when flexi hose is in the water, but what i can think of now is that the amount of water volume in the 2" PVC insufficient therefore before the siphon stops, the water inside has run dry thus causing the siphon to break. I assume you have replaced the end cap with one with hole on the highlighted green pipe. What I would do is to play/raise the 3rd "U" on the right so that siphon will stop early before it runs dry, but based on your design, you will have limited allowance for any adjustments. The post #5 will offer you more flexibility.

Probably you can post a pic of your current overflow tube?

We have many DIY Gurus that can offer advise here

[bobiegoh]

bro, I modified the design and this is my test result and attached is my modified design. Please help.

1/ if endcap is off, the primarily siphon will be immediately fail and pipe is empty.

2/ if valve is full / half open, auto restart will fail. Air pressure lost. Valve can only open 2/10, then auto restart work but flow rate is not high.

3/ I do not have hole on end cap.

[Morpheous]

The design of your overflow pipe is too short, very hard to prevent the break of siphon. Due to the pipe size and fast flow rate, the water in your 2" tube have sucked dry before the water stops. (Short reaction time for the water to slow down).

Below is how mine looked like (Tank is 1.5 feet height), Note on the difference between the cutoff level and end of the pipe.

u can take reference with the proportion of different cut off point and decide on a safety factor.

I have tried on a smaller scale before but failed, therefore I would advise you to make a bigger one as it is easier to prevent siphon break.

My opinion:

1)For your 2" tube, buy another cap to fit on the top, and use a hole saw to make a opening for the pipe or extend it to the bottom of the tank.

The pad will weaken over time and your tube will drop. Not fail proof.

2) The cap has to be removed when the overflow is running, else it will suck all the water in your 2" tube.

[bobiegoh]

yo bro,

Thanks for your advise but I can't see your pic clearly as it is too dark. I want to give up and am tooooo tired and sick of making the pipe again and again.

I made changes to the pipe as per advise. My tank height is 18" and water filled up to 15".

- Blue pipe in tank - 12" from elbow.

- Yellow pipe - 18" from elbow to elbow.

- Red pipe - 6" from elbow to elbow.

- Orange pipe - 10" from T to valve.

Is this ok or too short?

Why is it when I remove the end cap after siphon started, the siphon immediately stop?

[bobiegoh]

Sorry bro, the blue pipe should be shorten and therefore make the yellow pipe longer. This is the update design.... very tired of this..