Choosing the right injection pump

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shakenbake

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Aug 9, 2010
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Austin, TX
I've decided to start putting together a backup plan for the LQ in case I can't get enough chlorine into the pool with it. Right now it's running wide open with a 3/8" line and I'm holding 1ppm steady in a 40K gallon pool. I want the option to eventually use a chemical controller for PH (and maybe ORP since I don't have a SWG), which means the dosage will need to happen in bursts, vs. running continuously all the time (right?). In the mean time, I can use relays on my Aqualink to act as a timer for the pumps when the circulation system is on (which is 24/7 at about 25-30GPM), to run the pumps for shorter periods of time at higher flow rates.

Rate range - Chlorine
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For the low filtration flow rate I want to run to conserve power, our puck system has never worked, and I still have not been able to get TC to where I want it with the LQ. I don't have a good guess at what range of dosage I need each day. I know it will change depending on a lot of factors, especially temp. We have a UV system that will also burn off some of the Chlorine, and hopefully will let me run 1-1.5ppm of chlorine.
For the sake of argument lets say I use 2 gallons per week. A high pressure 22GPD unit will let me dose that much amortized over each day in a 20min/day block running at it's highest output rate, or about 5 hours running at the slowest speed.
Should I be prepared to run more than 2 gallons per week? Is a burst of chlorine in a 20min block each day the right way to go, or to apply over a longer period? Will that work with an ORP control system? I looked at the Jandy C1900, and as best I can tell it like the dosage to be in the 10min or less range, or continuously.

Rate range - Acid
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My TA is high (I think due to Austin water and our pebble tec, new pool), so I've been adding dry acid once a week - about 60 volume oz, which is about the same as muriatic acid.
So given that, with the same pump 22GPD, the dosage could happen in 5min each day spread across the week, or 2 hours at the lowest speed.

Pressure:
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I'm assuming I do not need a high pressure unit if it's injecting after the filter/heater? Correct? The units seem to come in low pressure 0-25psi and high pressure 25-100psi.

Pump Choices (Stenner, all are $250):
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45MHP22 25-100psi, 1.1 to 22 GPD
85MHP40 25-100psi, 2 to 40GPD
45M3 0-25PSI, 1.1 to 22GPD
45M4 0-25psi, 1.7-35GPD
85M3 0-25Psi, 2-40GPD
(there are units that have lower flow rates)

Any advice would be much appreciated.
 
I have been happy with the LMI metering pump I found on ebay last year, it allows setting stroke length and number of strokes per minute to give a slow even flow of chlorine, best of all it was under $100 new in the box off ebay, a Stenner pump would probably work better, but the ones I have seen would also require adding a separate timer, not to mention the costs.. Here is a link to the thread on my set up new-metering-pump-project-t22358.html?hilit=lmi%20pump

Ike
 
Are you going to continue running the LQ once the dosing pump(s) are in place?

While I like to stretch the chlorine addition out over time, short dosing times aren't a problem. If you think about it, manually dosing is a very large dose all at once.

Since you run your filtering 24/7 I'd rule out the 40 gpd pumps. Even the 22 gpd is quite large.

If you lose 2 ppm of chlorine per day (which is quite common) then you'll need to add 1 gal and 1 quart of 6% chlorine per day to maintain your FC. With a 22 gpd pump you'd need to run it ~24 hours on the lowest setting or ~ 1 hr & 10 min on the highest setting.

If this is an indoor pool then you can adjust your dial setting and run time to match your loss.

Note: With the Stenner pumps, changing the tube number changes the pump size so if you need a larger or smaller pump you can change it fairly easily.
 
Bama Rambler said:
Are you going to continue running the LQ once the dosing pump(s) are in place?

While I like to stretch the chlorine addition out over time, short dosing times aren't a problem. If you think about it, manually dosing is a very large dose all at once.

Since you run your filtering 24/7 I'd rule out the 40 gpd pumps. Even the 22 gpd is quite large.

If you lose 2 ppm of chlorine per day (which is quite common) then you'll need to add 1 gal and 1 quart of 6% chlorine per day to maintain your FC. With a 22 gpd pump you'd need to run it ~24 hours on the lowest setting or ~ 1 hr & 10 min on the highest setting.

If this is an indoor pool then you can adjust your dial setting and run time to match your loss.

Note: With the Stenner pumps, changing the tube number changes the pump size so if you need a larger or smaller pump you can change it fairly easily.
Click to expand...

Do I need a high pressure or low pressure pump?
 
Here's my thinking on it. If you get the high pressure model then if you ever needed to use it elsewhere that had higher pressure you could. Since the units are close to the same price I went with the HP model. However if you know you're never going to have that situation either model will work.
 
I have the HP pump and it's only injecting into a ~10 psi pressure line and it's working great.

The flow rating isn't affected by pressure until it gets well above the max rated pressure. The only physical difference in the high and low pressure pumps in the same family are the pump tubes.
 
Ok, I went a little overboard.

Got two 45MHP22s with 1/4 black tubing and rain proof housings, grey 7.5 (acid) and 15 (chlorine) Gallon tanks, and a C1900. Got the C1900 for a ridiculous price, and plan to use it for PH control. I'll watch the ORP reading to see if it makes any sense to rely on (I'm dubious).

Should I mount the pumps local to the tanks (suction hose very short) or the C1900 (suction very long, but power cables are easier to mount out of harms/water way - will be on a GFI circuit in either case)?
 
Basic Layout I was thinking
c1900.JPG


More shots of the pad (kinda messy right now)
DSC_0210_209%20%282%29.jpg


IMG_0551.JPG
 

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JasonLion said:
Those are the standard Stenner tanks, quite nice but not double walled or anything else fancy.
Click to expand...

Yeah, the tanks are pretty cheaply made. And, most annoyingly, there is no way to tell how much liquid is in the tank.
They were very cheap (~$100) but mounted the pumps. The rola-chem tanks look nicer in that they are UV protected and still translucent enough to see the levels.
 
Yes, one of my families businesses is a janitorial supply company and one of the customers is the local small hospital who buys their laundry supplies in 15 gallon containers, so I asked the salesman that calls on them to see if he could grab an empty before they threw it out. After a couple of weeks timing worked out that they had empties when he was there and he was able to grab a couple of 15 gallon drums, one of which happened to be bleach so it was the one I used for this project. We have other customers that use the laundry program chemicals, but no others that use the 15 gallon size drums, most are motels which use the 5 gallon pails, or larger institutions like jails that use 55 gallon drums.

Ike

p.s. If you want one let me know and I will see if I can get the salesman to grab another one and ship it to you, I don't know how much shipping would cost, and would probably have to remove the haz-mat label, but it can't be much for an empty drum.
 
Got power running to the units. I wired a duplex plug to an area within reach of the power cords of the pumps. Each circuit is tied into a relay on Aqualink, interlocked with the filter pump relay.
Added 12 gallons of 6.5% clorox and 6 gallons of 31.5% Muriatic acid to the tanks. Checked the current FC and PH levels, and dialed in the number of minutes via a temporary schedule on the Aqualink that would add the right amount of chemicals. Worked out about perfect.

Right now I have them scheduled to come on for a specific number of minutes at night. I'll adjust as needed.
 
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