Dosing Pumps - Do they Siphon

dbl · May 15, 2017

I would like to lower my dosing line outputs closer to the waterline in my sump. I've always kept them high enough that they are never submerged when the pump is off. I wouldn't think a peristaltic pump would back siphon if the output line is submerged, but I would like confirmation. I use a GHL doser if it matters.

So, is it okay to lower the lines and help keep the sides of the new sump I'm about to install a little cleaner?

Thanks in advance for the help!

n2585722 · May 15, 2017

If it has 3 rollers siphoning is probably not an issue. It will not matter if it is submerged or not if the output tube opening is lower that the water level in the storage container it will still syphon if it is going to. I would test it to make sure though.

dbl · May 15, 2017

n2585722 said:
If it has 3 rollers siphoning is probably not an issue. It will not matter if it is submerged or not if the output tube opening is lower that the water level in the storage container it will still syphon if it is going to. I would test it to make sure though.

Good point and I should have added that piece of information. My dosing containers are lower than the level of the output lines.

kschweer · May 15, 2017

Most dosing pumps will not siphon. The rollers "pinch" the tubing not allowing it.

Nicolas Sabrun · May 15, 2017

It would keep them out of the water when pump is off for 2 reason. First, it may siphon back at some point. Second, whatever is in the submerged tube would get mixed with your tank water and it may also throw off your dosing amount. Not necessarily a big issue depending on size of tank and the product being dosed.

That s just my thoughts on it and the reasons why I am keeping mine out of the water.

jason2459 · May 16, 2017

kschweer said:
Most dosing pumps will not siphon. The rollers "pinch" the tubing not allowing it.

As mentioned above a 3 or more roller design is much less likely to siphon. A dual roller peristaltic pump has a higher chance and has siphoned on people.

Justin Aretz · May 23, 2021

4 years later .... for any new readers I’ll report that my Jebao dp4s will absolutely siphon or back siphon if the output and input are too far apart in elevation

n2585722 · May 23, 2021

Justin Aretz said:
4 years later .... for any new readers I’ll report that my Jebao dp4s will absolutely siphon or back siphon if the output and input are too far apart in elevation

Another issue is the tubing in the pump splitting and causing a leak. Make sure the pumps are above the highest level of your storage tanks and keep the output tubing above the water level. As you mention it is alway a good idea for the output tubing end to also be above the water level in the storage tanks. I have not had an issue with mine being below that level yet and I have had the tubing split in the pump. It usually causes a slight leak at the pump. Worst case is it will quit pumping at all but my pumps are well above the storage tanks So no chance of a siphon from the storage tanks. As you can see in the photo my pumps are on a wall behind my work bench. The storage tanks are under the work bench. Only three of the 5 pump are in use. I made enough slots for both tanks I have and only one of the tanks is setup and running at this time. This is in my garage about 35ft from the tank. The tubing to and from the tank are run through the attic in conduit to a wall plate in the wall by the tank. I have the tubing run for the other tank but it is not in place. I still need to build the stand, but I have other projects in front of that one.