Stenner dual head water changer - noticing uneven exchange

[blurry]

I was using a genesis reef water changer, after moving the stenner solution made more sense as the bins are 30 feet away and the tubing had to go through two sets of closets.

So I got the pump, Stener 170DMP4 dual head 120GPD: Double head - Fixed Rate Low Pressure

I kicked off a 50 gallon water change, checked on the APEX and notice the ATO was running a lot. checked the salinity and sure enough, it's low. Its about bout 2.6 gallons of mixed water low for a rough estimate of 2.5% of the water change. Today i checked on the first "normally scheduled" water change and noticed the ATO kicked in out of the normal rhythm shortly after starting the water change.

Anyone else seen this? Any thoughts on what could cause this? All I've come up with is air pulling in from one of the john guest fittings or the pump.

the setup:

75 gallon holding tank, RODI tube weighed down using the stenner weight. hole drilled correct size, snug fit. to be sure it didn't slip I put a 1/4" coupler in to hold it up (not much pressure).

about 7 feet from holding tank to pump, about 40 feet of tubing to tank

about 40 feet of tubing from tank to pump, about 15 to end of waste line

The new water going into the tank is above the water level, old water pull out is below the water, though not on the bottom of the tank.

thanks!

 

[Reefing Madness]

 

[Small triggers]

I sounds like your ato sensor is very sensitive, when your pump kicks on to take water out with how far it has to travel the ato is kicking on before the new water gets back to your tank...you need to set the ato to turn off when your WC pump turns on....

 

[blurry]

The sensor is very sensitive (avast pressure sensor) - I do not believe this to be the issue though.

1 - the lines are primed, removal and addition should be equal
2 - doesn't happen on startup
3 - on the large water change the ATO kept kicking in showing a long term imbalance

I'm going to swap the lines on the pump heads and do a 20 gallon this weekend to see if the issue inverts or not

 

[TropicalReefCorals]

It sounds most likely that one of the pumps could be pulling some air, or that there is an issue with one of the the pump sets. Since both pumps are on the same shaft, it is very unlikely that they would not be moving the same amount of water.

Try placing a couple of 5 gallon buckets in place of your sump and change water, and try to use your existing tubing with an arrangement that will be moving the water between the two buckets. With the pump running continuously, the water level should not change in either bucket. If there is an air leak on the suction side of either pump, you will notice bubbles in the output of that pump system.

 

[blurry]

I'll try that out this weekend if I can get to it. thanks!

 

[Chris155hp]

Following as I have the same issue it's off about 10-20 ml every min

 

[blurry]

I haven't had time to look at this, let me know if you find a cause.

 

[NeveSSL]

Are you using all ridgid tubing throughout?

Brandon

 

[blurry]

I'm using standard semi-rigid 1:4" tubing. No visible leaks. Straight runs except for two john Thompson fitting by the bins

 

[blurry]

So a year later I thought it would be nice to straighten this out. I called Stenner who indicated there is a +/- of 10% with little else to contribute.

Pump: Stenner 170DMP4

Measuring setup:
5 gallon bucket with RODI
both input lines in bucket
output lines to two 5 L vertex containers with markings

I tried the following:
swap wheel assembly
swap cases
swap 1/8" lines
Swap Peristaltic tube

In all cases the difference in flow rate followed the peristaltic tube - it appears there could be a variance in the tubes.

it is important to note that in fussing around with it the one tube always moved more water, though how much more varied in each configuration which leads me to believe there are other variances such as how "straight" the tube is.

Can someone who has a variance try something similar?

At this point I'm suspect of any peristaltic based water exchange being used without monitoring salinity. Understanding that the APEX DOS and LiterMeter can be calibrated, I prefer to have something that adjusts itself. In my case I can't put in the RENEW by Genesis Reef which is a system I had that was flawless due to where the holding tanks are relative to the tank.

I plan to add salinity monitor to the APEX and a second top pump which tops off with pre-mix. I plan to run the lower rate pump to supply the tank and have the second topoff pump add premix. This should keep things close.

 

[stlcard]

ive got the stenner dual head 100dmp4 and have not noticed any changes. i tested it monthly for variances when i refreshed my salt mix tank and found a near perfect exchange from the out head and the in head. ive since switched to triton method though and no longer do the daily water changes. i found it too frustrating to have to deal with alk,cal,mag variances/dosing changes from salt mix to mix. always used RC salt, they jjust have different consistencies in the alk and cal.

 

[blurry]

interesting the difference in variance!

 

[d2mini]

With any dual pump exchange system, you have to calibrate the pumps.
Even if both pumps are calibrated to each other on their own, having a longer run of tubing on one vs the other will make a difference.

 

[blurry]

The Stenner is an industrial motor with two heads driven at once, there is no way to calibrate the pumps individually

 

[steveb]

I know this is old... But, you are correct you don't calibrate the pumps. You look at the volumes they move per time period with all tubing and then determine the error between the two. You then adjust the salinity of the new saltwater to adjust for the error.