Monday, June 11, 2012

Acid Pump - Fine, I Give Up.

I've been working on an Acid Pump system to automate the injection of acid into my swimming pool.  There are a ton of details on this effort on my Swimming Pool page.  Well, it failed again today.  After a few months of perfect operation, all four of the check valves have failed and the pump itself is not priming at all anymore.  I replaced the check valves as they failed and now, the pump diaphragm itself doesn't work any more.  So, either I go through the process of getting the pump replaced again or just give up.

I give up.

That doesn't mean I give up on the idea, just that I'm finally going to give up on the Hanna Dosing Pump.  This darn thing isn't made from material that can withstand the chemicals it is supposed to be designed to handle and does little but fail annoyingly often.  Although it did work for a few months without a problem, I noticed that the stainless steel screws that hold the pump head on are starting to corrode, the steel around the rate control is starting to corrode as well.  The environment is just to harsh for this pump to work over a prolonged period.  Yes, I could do more work to isolate it from the environment, but what the heck?  They advertise a pump that is supposed to work with extremely harsh chemicals and it should do just that.

As my Accounting 101 professor told me a long time ago, there is such a thing as "sunk cost."  That's where you finally realize that putting more time, research, and money into something just isn't worth it and you kiss the previous effort goodbye.  Smack.  Goodbye.  Now, I'm back looking at peristaltic pumps.  I didn't like them because the devices can have a failure in the flexible tubing that the rollers use to create the pumping action. This would result in a bunch of acid being released into the pump head destroying that whole section of the device.  That's still a concern, but with a check valve on the pool side where the pressure is and a little help from gravity to allow the acid to drain back into the reservoir when a breech happens, maybe I can get this to work.  The big name in these devices is Stenner, but darn, they are really expensive.  There are other devices, some are available on ebay, mostly for use in aquariums.  I've got some more stuff to learn.

At least the knowledge I picked up on materials and environment can help me tell if something is actually going to work.  I'm going to dismantle the check valves I tried using to see what the heck happened to them.  They are rated way beyond the usage I put them to and worked real well for a short period; there must be something going on I don't understand....yet.  There were four of them in the flow path and they failed differently.  One would allow flow both ways; another plugged up and wouldn't flow at all; two of them would allow a little reverse flow; obviously, there is something odd here.  The problem is that they are small and sealed really well so dismantling them will be a pain.  I have a lead on a check valve that has a barbed fitting on one end and 1/4 inch MPT fitting on the other; that would be perfect for this application, if its construction can withstand the acid.  I can't get enough information on it though so I may have to buy one of the darned things to see how it's made.



  1. How about just using a gravity fed system where you store the acid at a higher elevation than the intake to your plumbing. You just need to mechanically crimp or uncrimp the flexible feeding hose to control the flow...

  2. Thank you for asking. I never did say why I chose the pump solution did I? I had four choices that I could think of. Gravity feed, a venturi in the water line, using the suction side of the pool pump, or an acid pump.

    The suction side of the pump would work if I watered down the acid, but I wanted to use the stuff straight to minimize my effort. The venturi could back up if there was an obstruction in the water feed, like a kid messing around in the pool. This would force pool water into the reservoir. The gravity feed couldn't over come the pressure in the pipes; a check valve would have helped both the venturi and gravity, but I still had to deal with the pressure problem and the break pressure of the check valve.

    Hence, the pump.

  3. i am a pool professional.

    We maintain over 50 commercial pools, and have done so since 1983. Automating a pool is really an easy task. not cheap but easy.

    All you need is a controller setup like a Hayward HCC-2000, and stenner pumps.

    The stenner pumps are designed for this duty and are used for years in our pools, with only the occasional tube change. This setup will automate both your sanitizer AND your acid.

    something else to look at is using a different chlorine. Cal-Hypo requires MUCH less acid as the Ph is much closer to 7.5 than Dichlor.

    The setup i described above will run you a little over $2K. Quit being cheap and trying to DIY something... it can kill someone.

  4. I don't know about most other folk, but I don't have $2000 setting around that I can put into a product that may or may not work. I've already had to have my wonderful variable speed permanent magnet pump replaced under warranty because it failed in a manner that isn't in the documentation. The guy that did the work said the reason I had the pump replaced was because they ran out of repair parts in my district for this pump. Not a good sign.

    And, notice that I have the top of the line pump from Hayward, hardly the cheap way out.

    The Hayward device is probably a good one, but I really don't want to dump $700 or so to find out it has the same kind of problem I've already encountered. If you look at the various ads and reviews of the pump I gave up on, it is 'designed' to handle chemicals a lot more toxic and corrosive than what I subjected it to and is used extensively in laboratories all over the world. Didn't count for much did it?

    As for pool professionals: I had professionals put my solar water heater in, they plumbed it wrong and it took about $300 dollars extra and several nasty phone calls to get that (mostly) straightened out. The reason I say 'mostly' is because the system still only works through the pop-up cleaners because it would have taken much more work to get it inline with everything. I also had the pool controller (a Goldline) professionally installed. They didn't use the built in breaker panel and put a sub-panel by my mains. This means to turn the power off to the pool I have to leave the yard and walk around the garage to flip the breaker. Speaking of the very expensive, high quality, Goldline controller: it is also part of the Hayward company and has had the main board replaced twice under warranty because they designed the power supply connection too small and it keeps burning the circuit board. This is documented all over the web with various ways of repairing it. Seems everyone that has this board, has this problem and Hayward just waits for the warranty to run out so you have to spend the $450+ for a repair part. I used what I found on the web and repaired it myself the last time, I changed the manner of connection to follow the general rules for high current devices and it has held up for two years since the last failure. Funny how that works.

    So, excuse me if I don't want 'professionals' or 'pool specialists' recommendations.

    I want something that I understand, can get parts for, is supported by ME, works the way I want it to, and doesn't need a service call to fix; just drag out the meters and tubing and do it myself.