Siphon on 1/2” tube

[Wolters_88]

Like the title says, I'm trying to setup an auto water change with two separate pumps. One will go from my salt water bin and the other will run parallel to a drain from my sump in the middle of my basement. My issue is the siphon it would create. I see a ton of items to plug into a 1/4” but can’t find anything for a 1/2” tube. Any help would be appreciated. Thanks.

 

[Dennis Cartier]

I would put a tee and a reversed check valve right where the pipes/tubing exit the water in the saltwater bin and the sump. When the pumps are on, the head pressure keeps the check valve closed, as soon as they turn off, the suction opens the check valve and breaks the siphon. Be prepared for the check valves to leak a bit of water when breaking the siphon, so they need to be over the vessel with the pump, or have a hose extended into the air gap at the top of the saltwater bin or sump.

Dennis

 

[Wolters_88]

I would put a tee and a reversed check valve right where the pipes/tubing exit the water in the saltwater bin and the sump. When the pumps are on, the head pressure keeps the check valve closed, as soon as they turn off, the suction opens the check valve and breaks the siphon. Be prepared for the check valves to leak a bit of water when breaking the siphon, so they need to be over the vessel with the pump, or have a hose extended into the air gap at the top of the saltwater bin or sump.

Dennis

I will try this. Thanks

 

[Wolters_88]

I would put a tee and a reversed check valve right where the pipes/tubing exit the water in the saltwater bin and the sump. When the pumps are on, the head pressure keeps the check valve closed, as soon as they turn off, the suction opens the check valve and breaks the siphon. Be prepared for the check valves to leak a bit of water when breaking the siphon, so they need to be over the vessel with the pump, or have a hose extended into the air gap at the top of the saltwater bin or sump.

Dennis

Well this didn’t work. It continues to siphon.

 

[Dennis Cartier]

Hmm, you have a check valve on the line, reversed and above the water level, and the siphon is not broken? What kind of check valve are you using? Are you sure you mounted it in reversed position , arrow pointing towards your line?

This definitely will work to break a siphon, can you post a photo of how you have it setup?

Dennis

 

[Dennis Cartier]

Here is a video to help explain how to set it up and use it to deal with the siphon issue.



Dennis

 

[Wolters_88]

Hmm, you have a check valve on the line, reversed and above the water level, and the siphon is not broken? What kind of check valve are you using? Are you sure you mounted it in reversed position , arrow pointing towards your line?

This definitely will work to break a siphon, can you post a photo of how you have it setup?

 

[Dennis Cartier]

Ok, thanks for the video. My guess is that the crack pressure on the check valve is higher than the amount of suction on that diameter of hose can generate. Switching to a flapper style that uses gravity should fix that, but you will need to make sure it is oriented properly for the flapper to swing closed (install it horizontal with the hinge at the top).

Dennis

 

[Wolters_88]

Ok, thanks for the video. My guess is that the crack pressure on the check valve is higher than the amount of suction on that diameter of hose can generate. Switching to a flapper style that uses gravity should fix that, but you will need to make sure it is oriented properly for the flapper to swing closed (install it horizontal with the hinge at the top).

Dennis

I can’t find anything but slip to slip. Nothing that would work with 1/2” black vinyl tubing. Why I purchased what I have.

 

[Dennis Cartier]

Is the 1/2" OD or ID on the tubing?

 

[Wolters_88]

Is the 1/2" OD or ID on the tubing?

ID

 

[Dennis Cartier]

I see what you mean about only slip. I just looked at every valve on BRS and all slip fittings. My local LFS carries the same as the BRS ones, but in both slip and threaded.

Ok, to do this with BRS parts, assuming you are in the US, I would take a 3/4" slip flapper check valve and use a 3/4" spigot to 1/2" threaded adapter. Then to a threaded hose barb for your 1/2" hose.

See this page for the spigot adapter. https://www.bulkreefsupply.com/schedule-80-reducing-bushing-spigot-x-female-thread.html

I suggested the 3/4" to allow you to use a spigot adapter as it comes out much more compact than trying to do it with normal fittings and short pieces of pipe.

Dennis

 

[Wolters_88]

I see what you mean about only slip. I just looked at every valve on BRS and all slip fittings. My local LFS carries the same as the BRS ones, but in both slip and threaded.

Ok, to do this with BRS parts, assuming you are in the US, I would take a 3/4" slip flapper check valve and use a 3/4" spigot to 1/2" threaded adapter. Then to a threaded hose barb for your 1/2" hose.

See this page for the spigot adapter. https://www.bulkreefsupply.com/schedule-80-reducing-bushing-spigot-x-female-thread.html

I suggested the 3/4" to allow you to use a spigot adapter as it comes out much more compact than trying to do it with normal fittings and short pieces of pipe.

Dennis

I just tossed all the 3/4” pipe I had too. My pumps are only 400 GPH. Will these still close with it being such a low pressure?

 

[Dennis Cartier]

Closing the valve will be fine as long as the valve is installed to have the flapper swing closed by gravity. That will also make it easy to open with only a minimal amount of vacuum needed.

The spring in you current valve is just too strong for the vacuum created by the siphon to overcome. You could try moving the tee with the check valve closer to the pump as the vacuum will be highest there. Just make sure it is above the water.

Dennis