If you are in the water conditioning or water treatment industry, manage a store, or are an installation professional, odds are excellent you know more than most about pumps including chemical feed pumps. Here are a few things I’m fairly sure you didn’t know.
Most adults own at least six pumps:
- Fuel pump
- Washing machine (water pump)
- Oil pump
- Vacuum cleaner
- Dishwasher (water pump)
- Air conditioner
I’m sure I’ve left some out, but you get the point. Pumps are a very important part of nearly everyone’s lives. Below I’ve listed some historic information on pumps.
Pumps are not a new technology – only the power used to drive pumps (and control) are new. Pumps date back to Alexandria (Greece) 100 BC; animals, yes-even humans, powered pumps.
Christopher Columbus (1451–1509) used bilge pumps on his ships (pumps were made out of lead, with leather strips for flapper type check valves). It was written that he said “an efficient bilge pump was the most important piece of equipment on a ship”. I believe now we’ve established the historic aspect of pumps, it’s important we understand the basic classification of pumps.
Today’s water conditioning & w/ treatment installations include one or more of the above pumps. Centrifugal pumps are used for pumping large amounts of water, of particular importance in water recirculation. Piston pumps are of importance in water reclamation, such as reverse osmosis systems, due to their very high pressure capability. Displacement style pumps (diaphragm, or peristaltic), is a common way to pump chlorine, or other water treatment chemicals, we know them as; chemical feed pumps, metering pumps, chlorinators or injection pumps.
Now we’ve established the importance of pumps in our lives and in particular, the water conditioning & w/treatment industry, allow me to focus in on pumps used for chemical delivery in our industry. Although these pumps are properly called displacement, pumps (remember) both reciprocating diaphragm, and rotary peristaltic, in this article for diaphragm pumps I will use the name; chemical feed pump, the rotary peristaltic is often referred to as a tube, or squeeze tube pump, I’ll just use the name peristaltic pump.
Now that we’ve covered some of the history, I’d like to share some of what I’ve picked up over the years. Working for a well-known chemical feed pump manufacturer for thirty-three years has taught me quite a lot. Some of what I have learned may be valuable to you, a water conditioning & treatment professional. I would like to clear up some myths, or assumptions I’ve been asked about from time to time.
Do you as a manufacture build in planned obsolescence?
Nothing could be further from the truth; to the point, the question is almost humorous. When a particular chemical feed pump is designed, there are countless kinds of destructive testing conducted. We deliberately try to cause the product to fail. Product improvements are an ongoing process that just never ends. When we force a breakdown, that particular part or area is redesigned until it’s corrected.
Metering pumps should be trouble free.
Of all your equipment you work with, the metering pump will require the most attention. The model you purchase is important, and the brand reliability, remember you are dealing with far more than a mechanical pump, you are dealing with; water chemistry (ph & chlorine levels, to name a few), the possibility of serious bacteria, water temperature & pressure, and a multitude of other factors. When you put them all together, there is far more involved than a chemical feed pump. The “perfect chemical feed pump” will not overcome a poor installation. If any of the above items are neglected your job will become infinitely more complicated.
Which type of pump is better, peristaltic or diaphragm?
As a manufacturer of both I can tell you with some expertise they both have their strengths and weaknesses. I will also tell you there really is no definitive answer. It would be similar to asking what’s better a Jet pump or a Submersible pump? Peristaltic pumps are a bit easier for the novice, but if not maintained are far more problematic than diaphragm pumps. If you have a good working knowledge of diaphragm feed pumps, and understand the basics of maintaining check valves, this type pump is more cost-efficient. I believe in choice, and I’ll let the market decide that question.
Chlorine is on its way out.
We have a Love/hate relationship with Chlorine. This is a case where the good definitely outweighs the not so good. Don’t even try to imagine our lives completely without chlorine as a disinfectant. Alternative forms of disinfectants play a larger role in our industry, and that is a good thing. However, make no mistake chlorine is still the disinfectant of choice in our industry, it simply works well and the cost benefit isn’t worth arguing.
Most water conditioning & W/treatment professionals have their favorite type of chlorine. As a manufacturer, I do too. Let’s go over them. Liquid chlorine (sodium Hypochlorite) is usually purchased at your favorite dealer/distributor, or chemical company, some regions the chemical is delivered on a route basis. This industrial strength chlorine runs anywhere from 9% to 15% active chlorine. The chlorine you purchase at the supermarket is considerably weaker about 5% chlorine. Sodium hypochlorite, or liquid chlorine is the chemical of choice for most mechanical chlorinators, some will argue that point, but for the most part hands down its liquid chlorine. The problem with liquid chlorine is; it is heavy, cumbersome, and transporting it can be hazardous. Liquid chlorine weakens over time. Dry (chlorine) or calcium hypochlorite also has its advantages and disadvantages. It is certainly easier to store and does have a longer shelf life. Some of the challenges are obvious; you have to mix slurry (dry chemical & water), so it can be pumped. The amount of undissolved solids will over time foul check valves, and plug injection fittings. Peristaltic pumps are recommended if you choose to pump chlorine slurry. Peristaltic pumps easily handle chlorine slurries, because they have no check valves.
Some tips on maximizing the performance of your mechanical chemical feed pump (diaphragm, or peristaltic style)
- Keep variables to a minimum. Such as, chlorine strength, type of chlorine used, and the feed rate setting on chemical feed pump. Example; if you keep the chlorine strength consistent, during the summer months, you’ll need to increase the amount of chlorine to be fed. On a peristaltic pump, adjust the on time up (pump longer), with a diaphragm pump increase the cam setting, or pulse rate. If you tamper with chlorine strength (usually a problem with slurries), and chlorinator feed rate, you will just drive yourself crazy. Minimize your variables.
- Avoid running chemical container dry, while the pump may not be mechanically harmed, pumping air will cause the valves to build up a residue of dried chlorine (salt).
- After changing out chemical containers make sure, the chemical feed pump is primed and most air is purged out of the pump head & discharge line.
- At least every six months inspect, and if necessary, replace the diaphragm. Also, inspect the top and bottom valves; clean or replace. If you are using a peristaltic feeder, change pump tubes out regularly, Also keep your eye on the roller assembly; the rollers do require periodic lubrication, and replacement. Rollers that are frozen, not rolling correctly will dramatically shorten the life of the pump tube.
- Keep spare liquid ends (assembled pump head kits) handy, as we all know Murphy’s Law, “Problems usually occur at the most inopportune times”, it’s far easier to replace a diaphragm and pump head assembly with valves (usually just 4 screws) than detailing every o-ring and ball seat. Using peristaltic pumps? keep pump tubes and roller assemblies on hand. Time is money.
- Inspect the foot valve strainer quarterly, or as frequently as necessary.
- Chemical feed pumps are easy to prime when the discharge (pressure) line is removed or vented. After the pump is primed re-attach the discharge line to the top pump head valve, or close the vent relief.
- Keep the pump room clean & well ventilated – Too many pump rooms are a mess. The rooms should be neat & clean (not a storage area for junk) spare parts should be available at the site. An installation, instruction booklet should be mounted on the wall at or near the chemical feed pump, this will have a parts schematic complete with part numbers.
- Always wear eye protection when working on chemical injectors or when changing out containers, or adding chemicals. This is something that cannot be over stressed.
- Avoid changing chemical brands without researching the compatibility regarding your chemical feed pumps.
- A flow indicator installed on the suction tubing of your injector is an outstanding diagnostic tool, at a glance you can see if the pump is working properly. Some manufacturers offer them as standard equipment.
- Never mix different chemicals in the same solution tank.
- Never inject chlorine and pH adjusting chemicals near one another, always use caution.
- Your Chemical feed pump must shut down when the water recirculation pump is not running. The chemical feed pump should operate in concert with the water pump, never by itself.
- Chemical feed pumps – Double ball check valves just work better than single ball check valves.
- The weakest side of a diaphragm chemical feed pump is the suction side (the ability to draw chemical), always keep your suction run as short as possible (5’ or less). Discharge runs are not as critical.
- Most all warranty and out of warranty work is related to poor maintenance.
- Peristaltic pumps have an amazing ability prime, up to 18’ (without discharge backpressure), it’s true, but please keep the suction run a short as possible.
- Your pumps injection fitting is the single most neglected part of your system. When your injection fitting begins to clog, the chemical feed pump works harder & harder to overcome the blockage (sound familiar). Change or clean them regularly.
- Peristaltic pumps – Are easier (more forgiving) to use, but if neglected could be a serious problem. Pump tubes need to be changed with regularity; many are not & eventually could leak corrosive chemicals. Changing a pump tube is not complicated, and just takes minutes.
- Peristaltic pumps – Older peristaltic pumps benefit from changing out roller assemblies, as these rollers age (wear), slowly you lose critical squeeze tolerances and the pump gradually will lose the ability to inject chemical. Often the pump tube is blamed, but the problem is really the roller assembly.
- Suction & discharge tubing needs to be replaced regularly. This is one area where I see widespread neglect. Tubing is available practically everywhere and is rather inexpensive.
- Chemical controllers (pH, ORP & TDS) are of growing importance to our industry. This is an area you absolutely need to hire the most qualified, and service after the installation is an absolute. Most controllers work well with chemical feed pumps; Stick with the industry leaders, those controller companies with a proven track-record. Avoid elaborate so-called turnkey systems that claim to do everything. Caveat emptor.
- There is no perfect chemical feed pump or system – No matter the cost or what you were led to believe. The success of a particular job or system is directly related to the installer & quality of equipment, but most importantly how the equipment is installed & maintained. As a manufacturer, we do our best to manufacture the finest equipment, but we are only as good as those who do the installation, service & maintenance work.
In summary, pumps have a very long history dating back to 100 BC. Pumps are crucial to our lives, and particular importance to the water conditioning/treatment industry.
Robin Gledhill, President
Huntington Beach, CA, USA