Masterflex Dual Head - AWC - Unmatched Flow

[elfloyd]

In May I set up a Masterflex Dual Head pump for water changes, exchanging 2.5 Gallons per day.

In June I noticed my salinity was slightly increased. First thought was evaporation from the fresh salt water tank, so I started monitoring FSW salinity daily, and was especially careful to get the right salinity when making new FSW. No problem here, but I still saw a very slow salinity increase in the display tank.

Today I looked at the Apex graph showing off/on of the ATO pump, and noticed it stayed off about 8 hours after a water change. ATO normally comes on for about 10 minutes at two hour intervals.

I then checked the In and Out flow from the Masterflex pump. Over a two hour period the pump add 2.25 gallons of fresh salt water, but only removed 1.5 gallons.

I reversed the water lines.... same results, then I swapped pump heads... same results.


Here are the run lengths of the 1/4" tubing:

New salt water: FSW (10') > pump > Sump (50')
Old salt water: Sump (50') > pump > Drain (10')
​

At this point I can only assume the Masterflex pump heads are unable to push/pull equally when the distances are not equal.

Anyone experienced this?

 

[morganatlanta]

Yes. In my case, it would drain more than it would push up since my container and the drain are lower than the sump. I resolved it by putting the drain tube right at the ATO level, so it will just suck air.

 

[elfloyd]

Thanks Morgan... glad you found a solution. Hoping to find the root cause of the mismatch and not throw new equipment at the problem.

 

[lmm1967]

Makes sense that runs that different will show those results. That's a ton more friction for the pump to work against.


Sent from my iPhone using Tapatalk

 

[elfloyd]

The distance is the same so the friction should be the same. But one head pulls 50' and one pushes 50'.

 

[morganatlanta]

You could use a 50' roll of tubing instead of 10' on the short side of both runs.

 

[lmm1967]

one end has 10' then the pump - the other has 50' then the pump.

Pump is going to act differently if suction side is 10' versus 50'.

 

[Adam]

Is there a way to calibrate each side of the pump?
Or time the flow to get your desired results and set the run times up accordingly.

 

[enderg60]

Lmm1967;1094679 wrote: one end has 10' then the pump - the other has 50' then the pump.

Pump is going to act differently if suction side is 10' versus 50'.

Parastaltic pumps work in a way that tubing length will not matter. Once primed they will flow the same amount unless a tube is clogged. That is the whole point of them.

If both heads and tubing in the heads are exactly the same and they are on the same shaft they will flow the same amount. Check and make sure both heads and the tubing in them are the same and working.

 

[grouper therapy]

Could one be loosing prime (partially even) and actually pumping nothing until it primes which would give it a deficient. Possibility since it is 50 feet from the tank.

 

[enderg60]

Hmm didnt think about that but it could be a leak in the tube somewhere and/or its sucking in air and water.

Volumetric flow rate will remain the same but when some of its air.....

 

[elfloyd]

anit77;1094680 wrote: Is there a way to calibrate each side of the pump?
Or time the flow to get your desired results and set the run times up accordingly.

One motor turns both pump heads at the same rate. The pump heads are not adjustable.

 

[elfloyd]

grouper therapy;1094692 wrote: Could one be loosing prime (partially even) and actually pumping nothing until it primes which would give it a deficient. Possibility since it is 50 feet from the tank.

Each tube is one piece with connectors only at the pump and fresh salt water tank. I've tried different tubes with the same result.

 

[elfloyd]

Pulled apart and rebuilt all the connectors. No change. I have more pump heads laying around, I need to see if I have two that match and test again. Problem seems to be isolated to the old water suction side.

 

[grouper therapy]

elFloyd;1094731 wrote: Pulled apart and rebuilt all the connectors. No change. I have more pump heads laying around, I need to see if I have two that match and test again. Problem seems to be isolated to the old water suction side.

I assume the pressure of the roller against the tube is what prevents loss of siphon. can that be adjusted? it seems there has to be air entering some where to make up the difference in output. Like Ender mentioned the design negates friction loss.

 

[Adam]

I looked up the pump and I was thinking the same as David, roller pressure. Wouldn't think it would take much on the loose side to make a big difference in output over time.

 

[elfloyd]

No, roller pressure can not be adjusted.

 

[enderg60]

you change the roller pressure by using a tube with a thicker wall.

Are the tubes inside the head the same?

 

[elfloyd]

Tubes inside are the same... Cut from the same piece. I have another pump and two additional heads I'll set up tomorrow and test again.

 

[elfloyd]

EnderG60;1094742 wrote: you change the roller pressure by using a tube with a thicker wall.

Are the tubes inside the head the same?

Some Masterflex heads are adjustable (adjustable occlusion)... What I have are not adjustable. Yes, changing tube thickness will change pressure applied by the roller.

I'll try another pump and differs heads tomorrow... If that fails I'll try adding a small gate valve on the FSW suction side.