Help with Dialing in the Dosing of a Stenner Pump for Chlorine...

[GoGrabTheNet]

Though this is the SWG forum, it lists chemical dosing pumps as a potential topic to be discussed, so here I am!

First of all, I have a Stenner 45MPHP10 pump for automatic chlorine dosing. It's a 10GPD unit, 100psi. It pumps 10% chlorine solution, which is the kind sold at Lowes/HD in the 2-pack box. Strength is very strong and fresh.

Something is going on with either my calculations, the actual dose rate, or a combo of both.

Preliminarily, here's what we're looking at: 10GPD = 1,280oz/day = 53.3oz/hour = 0.89oz/min. Seems straight forward...

To get my daytime FC loss rate, at sunrise I measured the levels in the pool water to be 12.5 ppm FC. And the end of the day, after the sun has set and no longer shining on the water, I remeasured the levels. FC = 9.0 ppm. So unless I'm going about it wrong, the total FC loss during the day is 3.5 ppm.

Therefore, for my 13k gal pool, to raise the FC a delta of 3.5 ppm, it would equal 58 oz of 10% bleach (PoolMath). Calculated run-time of the Stenner would be 65 minutes.

My goal, however, is not to raise the levels but to maintain. With that in mind, is a 3.5 ppm loss over a 12 hour period the same as a 3.5 ppm "maintenance loss," i.e. a 58-oz dosing, regardless?

I ask because I set my Stenner pump to run 3x during the day, with each run-time equaling 22 minutes (66 min total). Programming is done with the Wion Woods timer/app. First run was 8AM, second at 1PM (blazing sun), and third at 6PM.

At the start of the day, ready for the dosing test, FC measured at 9.0 ppm.

At the end of the day today, the pool water tests to be 12.5 ppm FC!

So how the heck did the FC level rise a total of a 7 ppm? That would take 116 oz of bleach and a run time of 131 minutes--no way!!! How is that even possible; 9.0 START - 3.5 LOSS + 3.5 DOSE = 12.5? Say what??!

My goal is to maintain a level of 9.0 ppm FC.

NOTE: I should mention that the day was partly sunny today and quite hot in the afternoon. Pool water is about 95F. Also worthy of a mention is that the variable-speed pool pump runs at 1800RPM at the 8AM dosing time and 1300RPM at both the 1PM and 6PM dosing times. (1300RPM is just enough cranking power to idle the pump and move water, keeping energy bills lower during the peak timeframe while allowing mid-day debris with storms and winds to be sucked up by the skimmer). The Stenner's output line connects to the pressure side of the plumbing, downstream of the filter. I've noted that at lower RPM's, if the line (and check valve) is removed, then water does not spray out of the hole. It almost pulls a slight vacuum in the pipe and air is sucked in. I mention all this to question if the slight vacuum is somehow allowing more chlorine to be pulled into the plumbing.

EDIT: There is only a vacuum created if the diverter valve for the heater is not bypassed. For the timeframe outlined above, the heater was bypassed, and the opening of the hole does indeed spray out water. However, I did notice this: the Stenner check-valve/duckbill pinches off the water more efficiently at a higher water pressure than a lower pressure. It does not seems like a typical check-valve. For example, if the pump runs at 1300 RPM, water backflows and dribbles out and/or creates a small stream. At 3000 RPM, on the other hand, water just occasionally drips. This could be a problem. I'm debating if the check-valve/duckbill is even necessary. It seems like a good safeguard, but it may be more trouble than what it's worth. But how could that cause more chlorine to flow?!? Still scratching my head on this one...

Thanks for helping me figure this out!

 

[glo76]

Can't fault your math. Your runtime is similar to mine with the same pump (I run 75min/10% to get 3.5 ppm in my 15k pool). How often have you repeated this test - just once or do you see the same results over multiple days?

Just some things to investigate: flow rate is dependent on the size of the tube inside the pump. Could be that you were given the wrong tube size and are getting double the flow rate. Can always test by disconnecting the injector and flowing into a measuring cylinder for a set time to see if your flow rate checks out. Second is that your timer is faulty or has some hidden program causing it to run longer. Not saying either of those are the issue but just the first couple of things I would check out.

Ultimately if you have a problem at least it's the better end (too much flow rather than not enough) and you can always adjust the runtime based on how your setup behaves. Just monitor it for several days and adjust accordingly.

 

[GoGrabTheNet]

Can't fault your math. Your runtime is similar to mine with the same pump (I run 75min/10% to get 3.5 ppm in my 15k pool). How often have you repeated this test - just once or do you see the same results over multiple days?

Just some things to investigate: flow rate is dependent on the size of the tube inside the pump. Could be that you were given the wrong tube size and are getting double the flow rate. Can always test by disconnecting the injector and flowing into a measuring cylinder for a set time to see if your flow rate checks out. Second is that your timer is faulty or has some hidden program causing it to run longer. Not saying either of those are the issue but just the first couple of things I would check out.

Ultimately if you have a problem at least it's the better end (too much flow rather than not enough) and you can always adjust the runtime based on how your setup behaves. Just monitor it for several days and adjust accordingly.

Thanks, Glo76. No phantom timers; I recently deleted all of them to start fresh.

Well, the pool FC is back down to 9.0ppm tonight. I disabled the Stenner from running for the entire day to recheck the daily FC loss. No change from the previous 3.5ppm; it's the same today.

I just performed the "disconnected test." I ran the pump into a plastic measuring pail for 10 minutes on a countdown timer using the Wion app. Theoretically, 10 minutes runtime should yield 8.9 oz. of chlorine. However, tested actual yield was 10.5 oz...about 18% more than the "nameplate dosing." That puts the yield of the previous 66-minute runtime at 69.3 oz. instead of 58 oz.

But again, that's nowhere near the 116 oz. it would take to jump to +7ppm!

Second test is in the works now...a calculated runtime of 16 minutes using the actual dosing rate to raise the pool +1 ppm in FC.

 

[glo76]

How did the second test go?

Just some other thoughts, you might just have experienced some combined measurement error. Maybe your pool isn't 13k gallons but smaller so the FC rise is higher. You already determined that the Stenner puts out a bit more than you expected. Perhaps that partly sunny day only had a 2ppm 'load' vs the previous day 3.5ppm for whatever reason. Maybe you found some super-fresh chlorine that's 12% not 10%. All things together could potentially add up to the differences you are seeing calculated vs actual.

All just comes down to dialing it in over multiple days to get it where you want it. I'm an engineer and I tend to want to be precise over these things but ultimately the daily testing and slight adjustments are the best way to get it where you need it.

 

[rphpool]

I am the same way, you want to be precise but there are to many variables working here. Hot , humid , sunny days play havoc with chlorine. Then the next day hot , humid, cloudy. Then hot, humid ,sunny, cloudy , raining. See were I am going, it is all over the place. I just dial my Stenner into a range and check FC once to maybe twice per week. It usually bounces 1 to 1.5 ppm so no big deal. Also if you are using a 15 gallon barrel the chlorine will degrade over time in the heat. I will notice this when my FC drops over a couple weeks ( tank about half full ). Top off barrel with new chlorine and up it goes again. Just dial it into a range that keeps it sanitized and sit back and enjoy that margarita......and hurry before it melts!!!

 

[GoGrabTheNet]

I am the same way, you want to be precise but there are to many variables working here. Hot , humid , sunny days play havoc with chlorine. Then the next day hot , humid, cloudy. Then hot, humid ,sunny, cloudy , raining. See were I am going, it is all over the place. I just dial my Stenner into a range and check FC once to maybe twice per week. It usually bounces 1 to 1.5 ppm so no big deal. Also if you are using a 15 gallon barrel the chlorine will degrade over time in the heat. I will notice this when my FC drops over a couple weeks ( tank about half full ). Top off barrel with new chlorine and up it goes again. Just dial it into a range that keeps it sanitized and sit back and enjoy that margarita......and hurry before it melts!!!

Darn right! Plenty of margarita's being enjoyed over here!

Still dialing in my system...for the last couple days it has been cloudy or partly cloudy and rain!

I don't have a big barrel because 1) the ambient temperature and sun would cause too much degradation of the chlorine solution, 2) digging a hole deep enough for large barrel is very difficult in Arizona soil. So instead, I just have a black, 5-gallon bucket with a screw-on, sealed top (also black) that is buried about 3/4 of the way. I can fill it nearly to the top as I put the suction tube up as high as it will go without interfering with the screw-on lid. Theoretically, with a daily FC loss of 3ppm, then it should last 12 days or so. Kind of a hassle right now, but in the fall and winter, it should last much longer.

rphpool or glo76, are you guys getting white precipitate at the bottom of your chlorine tanks? What causes that? How can it be avoided?

 

[glo76]

I believe it's just salt coming out of the liquid chlorine as a result of its natural degradation. I'm not sure much can be done about it other than planning to rinse it out every once in a while. How much salt buildup do you see over what time period? I had my 15 gallon tank for a year, definitely noted some but it wasn't a particular problem - it stays as a very fine salt, doesn't crystallize or form a hardened deposit.

Some chlorine sources might be more susceptible than others - do Lowes/HD store their chlorine outside? It may already have started degrading when you buy it. Might be worth looking for other sources in your area that have indoor tanks (I get mine from pinch-a-penny).

I just had to install a 30 gal tank because I'm starting a new job and will be away for ~30 days at a time, wife didn't want to mess with refilling the smaller tank. I expect to see more problems storing that much in a tank in Houston summer heat.

 

[GoGrabTheNet]

I believe it's just salt coming out of the liquid chlorine as a result of its natural degradation. I'm not sure much can be done about it other than planning to rinse it out every once in a while. How much salt buildup do you see over what time period? I had my 15 gallon tank for a year, definitely noted some but it wasn't a particular problem - it stays as a very fine salt, doesn't crystallize or form a hardened deposit.

I was thinking it was some sort of salt as well, similar to what folks with the Liquidator experience at the bottom of the reservoir. You're correct that the salt is very fine and does not form hard crystals. In my tank, it seems that it forms rather quickly, basically in one or two days. From the store, the liquid pours a clear yellow into the tank/bucket. From then, if checked the next day, some salt has already formed and settled out to the bottom. Also, oxidation is occurring in the tank/bucket as well, as bubbles are gassing up almost at a "flat beer" rate! I'm sure the ambient heat is doing this, but what am I going to do?! There is no escape!

Some chlorine sources might be more susceptible than others - do Lowes/HD store their chlorine outside? It may already have started degrading when you buy it. Might be worth looking for other sources in your area that have indoor tanks (I get mine from pinch-a-penny).

For the most part, both Lowes and HD store the pallets of chlorine outside, but recently HD has been keeping a pallet inside...and it's super fresh. Therefore, I've been buying from HD, and these are the gallons that have been "salting out." I'd be curious to see what regular Clorox does...but it's more expensive and my tank would drain faster due to the lower concentration.

 

[GoGrabTheNet]

UPDATE: Well, here's another update on the Stenner dosing problem. I tested the pool water this morning, and it measured 18.5ppm FC + 0.5ppm CC...no freaking way! And the tank/bucket was nearly drained! The Stenner was programmed to run for a total of 48 minutes yesterday, broken up into 3, 16-minute blocks. FC prior to the day was between 9.5 and 10.0. Per PoolMath, it would have taken 141oz of chlorine to move from 10.0 to 18.5! Even if the day was completely cloudy and the water was ice cold (neither the case!), then going from 10 to 18.5 still isn't possible! The Stenner should have only output 50oz!!! What the heck is going on?!?!

There has got to be some sort of pressure-differential thing going on is causing the Stenner to basically puke out massive amounts of liquid beyond its rated capacity. I think an email to the company is in order. I don't think the Woods Wion timer is to blame; It seems pretty reliable.

With that in mind, yesterday's dosing had one block of 16 minutes occur in the morning when the pool pump was running at 1800RPM. This is where I've confirmed a dosing rate of about 1.05oz/minute. The other two blocks of time occurred when the pool pump was running at 1300RPM, just putzing along during the peak of the day. I think this is when the "mega-dosing" occurred. My suspicion is that the dosing rate is significantly greater than 1.05oz/minute at this lower pump speed.

I'm going to let the pool's water burn down to 10ppm, hopefully by this weekend, and have the Stenner dose for a period of 16 minutes at 1300RPM, expecting to only see a pool FC rise of 1.0ppm. Another test may be to fill a measuring container with a known quantity of water (e.g. 64oz on the dot) and stick the Stenner intake tube into it and see how much the quantity is reduced. Anything more than a reduction of 17oz for a 16-minute runtime and we got a problem!

 

[glo76]

Ok it sounds like there's some siphoning going on that your check-valve isn't preventing. I don't see how pump rpm would have an effect, especially lower RPMs being worse - the reverse would be more intuitive. My only other suggestion is if your bucket is not allowed to breathe (i.e. you just have the pickup tube) the pull from the Stenner may be setting up a siphoning situation. Can't work out the science but adding a breather hose might solve the problem. Otherwise I think a call to Stenner is in order.

 

[GoGrabTheNet]

Ok it sounds like there's some siphoning going on that your check-valve isn't preventing. I don't see how pump rpm would have an effect, especially lower RPMs being worse - the reverse would be more intuitive. My only other suggestion is if your bucket is not allowed to breathe (i.e. you just have the pickup tube) the pull from the Stenner may be setting up a siphoning situation. Can't work out the science but adding a breather hose might solve the problem. Otherwise I think a call to Stenner is in order.

Indeed the bucket is pretty air-tight. However, it is below the level of the Stenner pump by about 3 feet. Therefore, siphoning shouldn't be an issue. And I also don't believe that the bucket and lid combo is so air-tight that heat from the mid-day sun is causing positive pressure to build up. Something to think about for sure though. A small 1/16" hole near the hole for the tube may help.

 

[Teald024]

There has got to be some sort of pressure-differential thing going on is causing the Stenner to basically puke out massive amounts of liquid beyond its rated capacity. I think an email to the company is in order. I don't think the Woods Wion timer is to blame; It seems pretty reliable.

With that in mind, yesterday's dosing had one block of 16 minutes occur in the morning when the pool pump was running at 1800RPM. This is where I've confirmed a dosing rate of about 1.05oz/minute. The other two blocks of time occurred when the pool pump was running at 1300RPM, just putzing along during the peak of the day. I think this is when the "mega-dosing" occurred. My suspicion is that the dosing rate is significantly greater than 1.05oz/minute at this lower pump speed

The Stenner is basically a positive displacement pump. The rollers pinch the tube and push "pockets" of fluid down the tube. If working properly, there shouldn't be a way for extra fluid to push its way through the tube. The Stenner you have is capable of pushing fluid into a 100psi pipe. That means the pressure inside the barrel would have to greatly exceed this pressure to get past the rollers and through the tubing. I'm going out on a limb (a short one) to say the pressure inside your barrel is not above 100psi. Siphoning isn't really possible for the same reason. Both these comments are based on the assumption that your pump head is working properly.

You are assuming the timer is working properly and not running adtl minutes or more than 3x times a day. How about you do a test and pull the timer out of the system for a couple of days. You could manually dose 2x or 3x a day, use a stopwatch and manually turn the Stenner on and off. Measure the FC in the morning before the first dose and the following night and see what your 2 day average is. That would prove that it's not your timer.

Never forget Occam's razor


.

 

[GoGrabTheNet]

You are assuming the timer is working properly and not running adtl minutes or more than 3x times a day. How about you do a test and pull the timer out of the system for a couple of days. You could manually dose 2x or 3x a day, use a stopwatch and manually turn the Stenner on and off. Measure the FC in the morning before the first dose and the following night and see what your 2 day average is. That would prove that it's not your timer.

I'm not fully ruling out the timer just yet, but I did perform a test at work just a bit ago, setting the timer to run for two minutes, twice, to confirm start and stop times. The wife reported that the pump started and stopped right on the nose of the programmed times. One test was while the phone was on, and the second test had the phone in airplane mode. The Woods WiOn timer should work via a cloud and not have to be constantly tethered to the smartphone/app. It appears that this is indeed the case as the pump performed as expected even with the phone in airplane mode.

More tests forthcoming tonight...

 

[CaptainCannonball]

Are the rollers fully expanded? Also, a defective/worn tube could let a siphon condition exist, although it would only happen if the Stenner was not plumbed into the pressure side.

 

[bard]

Another thing to consider is that your pool may be smaller than advertised. This would cause overdosing. Try manipulating the volume in the calculator until the pre/post chlorine level matches reality. My advertised 18k pool is more like 12.5k based on how it reacts to chemical additions.

 

[GDN]

My bet is that it is the timer or some other issue than the Stenner. It's nice to be able to inject the chlorine in several times throughout the day, but it's not required as long as you stay above your minimum. So remove the timer from the equation and start/stop the stenner manually for a few days. Check your chlorine and see how it's working out.

On a different note - I like the math and calculating exactly what the stenner should be putting out, but that isn't reality. Someone else also noted to do a real test on what it pumps. Pump the chlorine or move the siphon end to a bucket of water - and pump for 10 or 20 or 30 minute intervals and measure exactly how much liquid you pump.