Using a Peristaltic pump for Acid

[lovingHDTV]

I've been thinking of adding a pump for acid injection into my pool.

I need to inject about 1 liter of acid per week. I've been trying to figure out how best to do this?

Initially I thought of injecting it into the skimmer basket of the main pool pump when it is running on high. I could inject at such a low amount that the dilution with the water won't affect the pump or plumbing. However, I would need to somehow ensure that there could be no injection if the pump was not running. This could be done with a simple solenoid off the pump switch to inject the acid. Not sure I really like this idea.

I could inject it into the pool return line. At this point I would just hook up the acid injection into the pool return line then put the peristaltic pump on a timer and let it inject away. If the pump was not running I don't think it would affect anything as it would just be in the PVC pipe of the pool return line.

I could hook it up to the autopilot pump control and inject prior to the chlorine cell, just like AutoPilot would do if I had their version of it. By doing this I know that the pump is running, because the AutoPilot is powered only when the low speed pump is running. I kind of like this as it ensures that the injection wont happen unless the pump is running, it will inject post pump, filter, heater. It will inject pre spa return, but I don't run the pump on low when using the spa. I think I like this the best of all.

No matter which way I go, I need to understand how the pump injects the proper amount then stops. I'm not familiar with the pumps so don't know how they work. Do they just run at what ever speed they are set at, then you use power to turn them on and off? Can you set them to inject a given amount of solution, then stop until the power turns on again? Is it totally pump specific? How would this work?

Does any of this make sense?

thanks,

 

[Guest]

Re: Using a Peristaltic pump for Chlorine

The pump continuously injects small amounts of whatever you are feeding as long as the pump runs. It's sort of like an IV drip bag but but it's not relying on gravity feed but rather a pump.
Often, once you get the feed amount right this is all you need to maintain your desired pH or FC. (You still need to test on a regular basis)
If you want to control it more by turning it on and off when the desired FC or pH is reached and back on when they are off target you would need to add an (expen$ive!) ORP and pH controller and electrodes and the electrodes become another maintenance expense. Also, IMHO, you still need to test on a regular basis!

 

[JasonLion]

One good way to set it up is to use a standard pump timer to control how long the acid injection pump runs. You set it up to inject acid at a fixed, very slow, rate and then adjust the daily run time to control how much total acid gets injected.

 

[Aquaman95]

Re: Using a Peristaltic pump for Chlorine

I would avoid injecting prior to the salt cell when it is generating chlorine. Electrolyzing low pH solutions tends to create quite a bit of hydrogen.

But, check with Autopilot to be sure on this. They may have a timeout built into their electronics.

Regarding how peristaltic pumps operate, there are generally two varieties. One variety slows down the motor of the pump either electronically or mechanically. To use this pump it is basically "trickle feeding" whenever it is on and it is the most common method. A timer can be used to control it in addition to tying it into a flow dependent power source if you need to restrict pumping further than the lowest setting on the pump. With weekly injection of 1 liter this is probably what you'll need to do.

The other variety have electronic controls that inject based on external input (ie a flow or pressure switch tells the pump that flow is in the line and then the pump injects whatever is set in it's batch process). These are not as common and are usually a bit more expensive.

 

[lovingHDTV]

One good way to set it up is to use a standard pump timer to control how long the acid injection pump runs. You set it up to inject acid at a fixed, very slow rate, and then adjust the daily run time to control how much total acid gets injected.

Hm, I'll have to find some info on how the AutoPilot pump timer works. If I could set it to run for a fixed amount of time each time it turns on I should be good to go.

Off to figure out how to use the pump timer on the AutoPilot, hopefully it is an amount of time thing, not a fixed time of day thing . . .

thanks,
dave

 

[lovingHDTV]

Me again after playing with the AutoPilot controls.

So the time of day is sticky as is the pump program so it stays set through a power off. Makes sense.

I can then just go in and program the pump to run during the time of day I have the AutoPilot programmed for with my main timer. This will then only inject acid when the pump is running and if someone overrides it, nothing bad will happen. At worse I'll miss an acid injection.

I plan on continuing with my weekly testing after it has stabilized out. Hopefully this will help with my keep up of the pool. For the last two seasons I've had to add a consistent 1 liter of acid per week. With this enhancement I should be golden

 

[lovingHDTV]

Well I was able to get a pump off Ebay for $50 shipped. It is a MityFlex 907

http://www.globalspec.com/FeaturedProdu ... Pump/709/0

I wanted something right around 20ml/min and I should be able to get this from the pump per the specs. This lets me run the acid pump for 6 minutes per day to get close to my quart per week that I need.

Now off to find tubing to use. I saw some at McMaster-Carr that should work a Tygon PVC I believe. Anyone else have a suggestion for tubing to use?

 

[lovingHDTV]

I'm looking into the proper tubing to use with the muriatic acid.

Looking at compatibility charts it looks like HDPE tubing and fittings should work fine in this application. I also saw that this is the plastic used in the jugs of acid that I buy from the pool store.

Unfortunately, I've not been able to find a black version of the tubing. I was looking for black because it is supposed to be more UV resistant than the natural or white colors. Anyone know a good place to get some? I looked at usplastics, and while they have LDPE (not good for muriatic acid) in black, they don't carry the HDPE. They do however have all the fittings needed in HDPE (black).

I looked at Tygon tubing but is the PRICEY! Would be like $30 just for tubing.

Any other suggestions of tubing that is UV resistant that would work here? What is used out there in the "real" world?

EDIT: I found some UV resistant Tygon tubing at usplastics that should work. Still looking for comments on tubing

thanks,
dave

 

[lovingHDTV]

Another Update:

I got all the electrical finished up today and tested the Autopilot controlling my peristaltic pump. It work beautifully!

I'm now waiting for my order from USPlastics. Apparently the 5 gallon storage container I ordered is back ordered. Thought I looked again today and it shows it in stock.

I'll post some pics when I get it all done.

 

[lovingHDTV]

Question for ya'll.

I'm getting a 5 gallon container to store my acid in. I'm thinking about mixing it to a 1:4 acid:water mixture. This would allow me to put 1 gallon of acid in the container then dilute to fill the 5 gallon container.

I'm thinking of doing this as a safety precaution. My fear is if something goes wrong and the relay gets stuck open and I end up pumping the entire container of acid into the pool, doing so with 5 gallons of acid would be much worse that just 1 gallon.

Does this make sense?

If so, I think you are supposed to always add the acid to water. Is this correct also? I'm thinking of when I refill the container, there will be some residual left over from the previous batch. Should I then fill it to the 4 gallon mark with water, then add the gallon of acid? Or could I add the acid first then fill up with water?

Not sure if it matters, but would like to know if it does. I know some of ya'll do this with the AutoPilot Total Control system.

thanks,
dave

 

[JasonLion]

This sounds like a good idea. Dilute acid will also have a far lower amount of fumes so opening the tank will not be nearly as annoying.

Add water then acid, and be careful. The acid remaining in the tank will be much more dilute than the new acid, so it is safest to add water to that, and then add the full strength acid to the nearly full tank.

 

[Ohm_Boy]

Still looking for comments on tubing

A little late, I suppose, but Cole-Palmer has a parametric tubing selector which identified this Neoprene
selection for a spec of 3/8" ID, Black, for media of 37% Hydrochloric acid.

 

[lovingHDTV]

Well I got it all hooked up and working. Not too happy with my storage container solution, but it appears to be working for now. But more on that later.

I ordered the following from USPlastics.com

5 Gallon HDPE container
Tygon UV Resistant 3/16"ID 1/4"OD tubing
1/8"NPTx3/16" HDPE elbow
3/16"x3/16" barbed connector
Norprene 3/16"ID 3/8"OD tubing

Cost:
$50 for peristaltic pump on Ebay
$80 for junction box and electrical stuff
$35 for USPlastics
$8 1/8"-27 NPT tap

$173 for the whole thing

The Norprene is used in the peristaltic pump. For my pump a 3/16"ID tube will pump 28ml/min. All other tubing, connectors, etc are made of HDPE as it has excellent resistance to muriatic acid.

I installed a dedicated 110V circuit that is hooked to my AutoPilot and is controlled as a two-speed pump. Basically all this does is tell the AutoPilot controller to turn on the pump relay when I program it to. This allowed me to use the AutoPilot controller to run the pump for the necessary time each day to pump the acid into the pool. For me it came out to 24 minutes per day. This was arrived at by knowing I need ~1quart of acid per week. I am diluting the acid 4 parts water to 1 part acid. I was then able to figure out the amount of time per day I needed to run the pump.

I then mounted a 8x8x7 PVC watertight electrical junction box on the side of the house to store the peristaltic pump. I then hooked up the Tygon tubing from the pump inlet to the storage tank, and from the pump outlet to the injection site just prior to the power cell. I used the place marked by AutoPilot as my injection site.

The storage tank did not turn out like I wanted. I initially wanted to drill and tap the top of the tank, then put a pickup tube that would go from the top connector to the bottom of the tank. This meant that if something leaked I would not loose all the acid. I picked the 1/8"npt elbows because the inner diameter of the threaded end is 1/4" allowing me to have a nice snug fit for my 1/4"OD Tygon tubing as the pickup tube. The 1/4" opening on the elbow worked out very well and did in fact provide a nice snug fit for my pickup tubing.

Turns out that HDPE and Norprene for that matter float in water so my pickup tube just floated out of the water and I was pumping air. So I drilled and tapped a hole in the bottom edge of the tank to use that as the pickup. Well, you guessed it, it leaked. ARGS!!! So now I have a tank with a hole in the bottom and in the top. I had picked up some adhesive from Locktite that works on HDPE. Yes you can buy adhesive for HDPE now. I ended up using it to glue the pickup elbow into the threaded hole in the tank. So far it is holding, but I'm not 100% sure that it will resist the acid. Though with my dilution it is only 6.2% so maybe. . . If not I'll buy another tank and use the pickup tubing idea again. After thinking about it a little more CPVC has excellent resistance to muriatic acid and will not float. So if I need to I will put a CPVC elbow onto the end of the pickup tube to anchor it in the bottom of the tank. Wish I had thought of that before. . . I'm using the elbow that I put in the top of the tank as an air vent. Hopefully it won't allow for too much evaporation while allowing air to enter the tank as acid is removed.

Here are a few picts and some commentary.

Here is the pump installed in the junction box:

Close up of the pump connections:

1. I bought a cheap indoor/outdoor 16 gauge extension cord, cut the end off and used it to wire up the timer to the pump. This allows my to unplug the pump if need be for maintainance purposes.
2. I decided to put a single piece of Norprene in the pump, and make sure that there were no connections of the tubing inside the junction box. This will reduce the possibility of a leak happening in the box. Or so was my thinking.

My injector. Notice the 1/2" or so of tubing so that it injects into the center of the pipe.

Injection site. I figure if it is good enough for TotalControl then it is good enough for me.

Original hookup to the storage tank. This is now just open as an air vent with the pickup connector on the back side of the tank.

Here is the finished product. I used 1/2" pvc pipe zip tied to the 2" pvc pipe to provide guides for the Tygon tubing. The tubing is very supple and would kink if I trying to zip tie it directly to the piping.

 

[spriteman]

nice job HDTV --- very nice job! I've been following your thread since april anticipating pics .... and you delivered Since installing our pool pilot about a month ago the acid demand has gone up about 50%, so I'm looking for a more automated method of delivery such as what you have done.

As I understand it, you are using a single external timer to run your pump and pool pilot control box -- but, you are using the electrical connection to the pool pilot control board to run the peristaltic pump (the modified orange outdoor extension chord connection). is that correct? any chance you can snap a close-up of that electrical connection to the PP control box when/if you have the cover off?

would love to hear any additional comments you have regarding your set-up after a month or so of usage. again --- great job!

 

[lovingHDTV]

As I understand it, you are using a single external timer to run your pump and pool pilot control box -- but, you are using the electrical connection to the pool pilot control board to run the peristaltic pump (the modified orange outdoor extension chord connection). is that correct? any chance you can snap a close-up of that electrical connection to the PP control box when/if you have the cover off?

would love to hear any additional comments you have regarding your set-up after a month or so of usage. again --- great job!

I'll open it up tomorrow and take some pics of the wiring. Basically I have a 220v circuit coming from my external timer going to terminals 1,2 and ground on the AutoPilot. I then pulled a 110v circuit from the breaker box to the AutoPilot terminals 3 and 4. I hooked hot to 3 and common to 4. The extension cord is wired to terminals 5, 6 and ground with 5 being hot and 6 being common.

When you look at the AutoPilot controller you can easily see the big (like really big) brown and blue wires going from terminals 3,4 through a relay to 5,6. I just kept everything lined up.

I've watched the acid level the last couple days and it appears to be working as I can see how much solution is being pumped each day. I'll also be tracking my PH and TA through testing and hope to see the TA slowly dropping with PH staying steady. This part I'll just have to wait and see how it turns out.

 

[lovingHDTV]

Here is the picture of the AutoPilot control relay hooked up.

 

[spriteman]

I'll open it up tomorrow and take some pics of the wiring. Basically I have a 220v circuit coming from my external timer going to terminals 1,2 and ground on the AutoPilot. I then pulled a 110v circuit from the breaker box to the AutoPilot terminals 3 and 4. I hooked hot to 3 and common to 4. The extension cord is wired to terminals 5, 6 and ground with 5 being hot and 6 being common.

okay, great! the pic along with the above description did the trick. one more question: if your peristaltic pump had been rated at 220v would you have just used the 220v circuit from your pool pump timer to supply the acid pump electrical requirement instead of pulling a dedicated 110v line?

 

[lovingHDTV]

I'll open it up tomorrow and take some pics of the wiring. Basically I have a 220v circuit coming from my external timer going to terminals 1,2 and ground on the AutoPilot. I then pulled a 110v circuit from the breaker box to the AutoPilot terminals 3 and 4. I hooked hot to 3 and common to 4. The extension cord is wired to terminals 5, 6 and ground with 5 being hot and 6 being common.

okay, great! the pic along with the above description did the trick. one more question: if your peristaltic pump had been rated at 220v would you have just used the 220v circuit from your pool pump timer to supply the acid pump electrical requirement instead of pulling a dedicated 110v line?

Yep, I looked at them, but the one I got from Ebay ended up being 110v and no way to rewire it for 220v.

 

[lovingHDTV]

It has been a couple weeks now and everything is running without a hitch.

I've tested my water every couple days for PH, FC, and TA. It has been steady the entire time. This is quite new for me as I've always had a lot of PH drift. To counter the PH rise I've tried to keep my TA=~70 which is a pain as my fill water is 200.

My parameters now are:

FC 3.0
PH 7.8
TA 120
CH 400
CYA 60

and have been there steady. I'm fine with a TA of 120 if the PH stays there. I guess I could increase the acid strength and have a gradual decrease in TA, but for the time being I'm not seeing any issues.

dave

 

[spriteman]

dave, all your info has been helpful -- as I am seriously considering doing a set-up similar to yours. I'm a little confused as to what settings you now have in the pool pilot service menus regarding pump configuration.

prior to your integration of the peristaltic pump into your pool pilot setup, I assume you had the following settings (since you are using an external timer to control the pool pump):

PP service menu:

4.0 Installer Menu --> 4.6 Set Pump Config --> "External Timer"

What Pool Pilot service menu settings did you change after integrating the peristaltic pump into the system? I thought you couldn't set a "Pump Program" unless the "Pump Config" was something other than "External Timer" (e.g. One-Speed Pump, Two-Speed Pump, etc.).