I got a variable, but only have it set to FULL speed, and control it with a timer. I figured that if I didn't have to engage the slip gear, it wouldn't wear out.
I got the pump for a song... $80 brand new, and couldn't turn it down.
It was the SECOND best thing I have done for my pool, and my sanity!
The first best was following the principals that are taught here on TFP.
I love my stenner, and wouldn't hesitate to replace it at full price if it ever bit the dust.
I just got the Stenner Econ T to automate the chlorine and it works fabulous. It is fixed speed with a built in timer. Only other recommendation is to get a pump on the higher gpd end. This will reduce your run time and wear and tear.
I have a rola-chem but it's still the basic idea as a stenner. Mine is a fixed rate head but it has a timer built in with a control knob labelled 0 to 7. Since the pump can dispense 12 gallons per day, way too much, I put it on a separate intermatic timer from home depot so I could set the knob to about 3 and still have some room to adjust up and down.
I have an variable rate stenner pump. I purchased it on Craigslist and actually got two of them for $60 each. I have it set to the highest rate and control it with a timer. I run it twice a day for 20 minutes each to inject 1/2 gallon of chlorine per day.
I bought the 45MPHP22 fixed rate pump. I know my pool takes about 1/2 gal chlorine a day. The pump puts out roughly 22 Gal per day which equals 1.95 oz per min. I run the pump twice a day for roughly 16 min each time. I planned on using a timer to control how much chlorine is administered so the bigger the pump, ( flow rate ) = less the run time, less wear and tear, the longer the pump will last.
I bought the Stenner fixed rate 45MP2, 10 gallon per day, 25psi model attached to a 15 gallon tank from Poolweb.com for $366 shipped. It came in yesterday and I'm ready to install today. I'll be using a Wood's outdoor timer. Looking forward to this upgrade.
I purchased a variable 45M and use the small tube to dispense 16 total ounces over a one hour time period of a 50/50 muriatic acid solution. I regret buying the variable. It's too noisy for me and my neighbors due to the very loud clicking sound it makes on variable dosage settings. So I run it at full open without restriction and use a Woods Timer to regulate the time. The Woods timers don't last much more than a year in my experience. I like their precision and price point over the alternatives. I keep a backup on hand.
I do wonder if using the next size larger tube and running it for only 15 minutes would be a better idea? Or would those 8 ounces of acid be too much going into a 4 jet 17,500 gal pool in that period of time if someone were swimming in the pool?
I So I run it at full open without restriction and use a Woods Timer to regulate the time. The Woods timers don't last much more than a year in my experience. I like their precision and price point over the alternatives. I keep a backup on hand.
I’ve had two Woods timers fail on me (causing a serious acid dump, ie, stenner was on for the full time of the pool pump cycle. I really like the Wood timer design and price point, but reliability does become a really important factor in the context of timing the dispensing of acid. So I have two Woods timers - one controlling the other. This at least reduces the odds of another timer failure/acid dump, as this would only happen with a simultaneous failure of both timers. As an additional safeguard against a timer malfunction, I time th dispensing to be during the final 15 minutes of the pool pump cycle. If both timers were to go bad, referring to both going into a always on mode, dispensing would only occur during that pool pump on time frame (ie, timers powered by pool pump circuit).