Peristaltic pump

[jduong916]

If i use a peristaltic pump is there any reason why i can’t put the outlet under water in the sump? It seems like there would be no chance of siphon and leaving the outlet underwater would keep the end of whatever youre dosing cleaner.

 

[Crustaceon]

If i use a peristaltic pump is there any reason why i can’t put the outlet under water in the sump? It seems like there would be no chance of siphon and leaving the outlet underwater would keep the end cleaner.

If the outlet is already lower than the inlet, then there's no reason why you can't put the outlet in the water, as there is no siphon risk. I wouldn't bother however because it's not hard to clean the kalkwasser crust off of the hose and placing the hose under water will skew your pump's calibration.

 

[Gtinnel]

If the outlet is already lower than the inlet, then there's no reason why you can't put the outlet in the water, as there is no siphon risk. I wouldn't bother however because it's not hard to clean the kalkwasser crust off of the hose and placing the hose under water will skew your pump's calibration.

Unless I misunderstood what you meant if the outlet is lower than the inlet then it would start a siphon if not for the roller(s) in the pump preventing it. Whether the outlet is submerged or not doesn’t matter if lower than the inlet.
ETA- I just realized you meant it can’t back siphon. It still could and would siphon in the normal direction of flow if not for the pump rollers.

As I understand it the reason to not submerge the dosing line is because when the supplement (especially 2 part) hits the water it can precipitate if not quickly diluted. If your dosing line is submerged then it gets mixed with the water in the tube and causes more precipitation inside the dosing line.

 

[Crustaceon]

Unless I misunderstood what you meant if the outlet is lower than the inlet then it would start a siphon if not for the roller(s) in the pump preventing it. Whether the outlet is submerged or not doesn’t matter if lower than the inlet.
ETA- I just realized you meant it can’t back siphon. It still could and would siphon in the normal direction of flow if not for the pump rollers.

As I understand it the reason to not submerge the dosing line is because when the supplement (especially 2 part) hits the water it can precipitate if not quickly diluted. If your dosing line is submerged then it gets mixed with the water in the tube and causes more precipitation inside the dosing line.

Basically water is at the mercy of gravity and as long at the pump and the inlet hose are above the outlet level, water mechanically cannot flow towards the pump. So you can have the outlet hose under water and as long as everything attached to that hose is above where the hose meets the water, you’ll be fine.

 

[Crustaceon]

Unless I misunderstood what you meant if the outlet is lower than the inlet then it would start a siphon if not for the roller(s) in the pump preventing it. Whether the outlet is submerged or not doesn’t matter if lower than the inlet.
ETA- I just realized you meant it can’t back siphon. It still could and would siphon in the normal direction of flow if not for the pump rollers.

As I understand it the reason to not submerge the dosing line is because when the supplement (especially 2 part) hits the water it can precipitate if not quickly diluted. If your dosing line is submerged then it gets mixed with the water in the tube and causes more precipitation inside the dosing line.

You can also have precipitation issues where the 2-part comes into contact with tank water. I’m sure Randy could write a few pages on that.

 

[Gtinnel]

Basically water is at the mercy of gravity and as long at the pump and the inlet hose are above the outlet level, water mechanically cannot flow towards the pump. So you can have the outlet hose under water and as long as everything attached to that hose is above where the hose meets the water, you’ll be fine.

I don’t know that I agree with the at the mercy of gravity part since when a siphon starts it can go up the tubing to get to the lower end.

IMO it is not a good idea to put the outlet lower than the inlet and it is also a bad idea to put the outlet underwater even if it is above the inlet.

If the rollers in the pump fail to block the flow (which isn’t too uncommon as parts wear out) then if the outlet is lower than the inlet (either submerged or not) it will siphon the contents of the dosing container into the tank.
If the outlet is above the inlet and under water it will siphon water from the tank back to the dosing container.

The only truly safe solution (without check valves, but that’s a different topic) is for the outlet to be above the inlet and not submerged. That would cause the line to run empty and a siphon not be started if the pump rollers didn’t block flow.

 

[Gtinnel]

Also I should have mentioned that it is the height of the dosing liquid and the height of the outlet that matters in regards to a siphon and not where the inlet line starts (I learned that lesson the hard way).
Also the reason the keep the pump higher is to avoid it starting a siphon if the tubing leaks at the pump (either from the tubing inside the head or the connections to it). If it were to start leaking at the pump as long as the pump is higher it will allow air in the line and break a siphon.

 

[jduong916]

If the outlet is already lower than the inlet, then there's no reason why you can't put the outlet in the water, as there is no siphon risk. I wouldn't bother however because it's not hard to clean the kalkwasser crust off of the hose and placing the hose under water will skew your pump's calibration.

Just to clarify, there is no siphon risk because of the peristaltic pump? Not because of the differing inlet and outlet heights.

 

[Gtinnel]

Just to clarify, there is no siphon risk because of the peristaltic pump? Not because of the differing inlet and outlet heights.

That is correct that as long as the rollers in the pump head are pinching the line closed like they should be, then there is no chance of a siphon in either direction.

Just remember that if a roller wears out over time to where it doesn’t close the line off completely it would allow a siphon that can cause a major problem if your setup allows for it.

 

[jduong916]

That is correct that as long as the rollers in the pump head are pinching the line closed like they should be, then there is no chance of a siphon in either direction.

Just remember that if a roller wears out over time to where it doesn’t close the line off completely it would allow a siphon that can cause a major problem if your setup allows for it.

I use old dinosaur masterflex pumps. Pretty reliable with full steel rollers

 

[jduong916]

Unless I misunderstood what you meant if the outlet is lower than the inlet then it would start a siphon if not for the roller(s) in the pump preventing it. Whether the outlet is submerged or not doesn’t matter if lower than the inlet.
ETA- I just realized you meant it can’t back siphon. It still could and would siphon in the normal direction of flow if not for the pump rollers.

As I understand it the reason to not submerge the dosing line is because when the supplement (especially 2 part) hits the water it can precipitate if not quickly diluted. If your dosing line is submerged then it gets mixed with the water in the tube and causes more precipitation inside the dosing line.

That sounds like a pretty good possibility.