Diaphragm Type Metering Pumps Chemical Feed Systems

How Madden Chooses Wetted End Materials to Handle Sodium Hypochlorite

Madden has started posting articles on common chemicals being pumped via the JN, MF, and MH Madden Pumps. The intention of this blog is to walk the reader through our process as to better understand how and why we come up with our recommendations.

Some of the more common, harsh chemicals we receive inquiries on and build pumps for are sodium hypochlorite, chlorine dioxide, and sulfuric acid.

This blog will be on sodium hypochlorite.

Sodium Hypochlorite Characteristics

Sodium hypochlorite is similar to chlorine dioxide; it is used to purify water, bleaching, odor removal, and surface purification.

There is a document on Cornell University’s Cooperative Extension website that does an excellent job of describing sodium hypochlorite’s characteristics, scientific findings, uses, and a tolerance assessment. You can read this one page document by clicking on this link:http://pmep.cce.cornell.edu/profiles/miscpesticides/methylchloride-xanthangum/hypochlorite/hypochl_prf_0286.html

The Recommendation Process

At Madden, we rely on a combination of documentation and experience. The documentation includes checking the chemical resistance of wetted end parts using at least three different charts to verify that the diaphragm, valve seats, valve balls, and so on will hold up to the chemical being pumped. However, just looking at charts isn’t always the best route. There are 3 individuals with 20+ years of experience each at Madden and you can’t replace experience. We also rely on customer experience as well. There are some times where a chart will claim a material will hold up to a certain liquid and end users tell us this simply isn’t true. They see it in use and in the field and we adjust to this information. The opposite can be true as well; on occasion an end user will relay information to us stating even though material X is generally stated as something that can’t hold up to the liquid, they have never had a problem.

Quick Guide

Sodium Hypochlorite has several levels of concentration; the level of concentration in the process being pumped will determine the most cost effective way to design a pump to handle the liquid.

Normal concentrations of sodium hypochlorite usually fall between 10-15% where a Madden pump is concerned. So with this information, the following is a common wetted end we would prescribe for a customer’s application:

Solution Head: PVC
Diaphragm: Viton
Valve Seats: Viton
Valve Check Balls: Teflon

Also, for harsh chemicals like sodium chlorite, Madden always recommends a double diaphragm set up. This backup diaphragm essentially ensures that the chemical will never come in contact with the interior parts of the pump; allowing repairs to be minimal when and if needed.


Whether or not your process is what we consider “normal”, if you have a need to inject sodium hypochlorite or any chemicals into an application give us a call or request a quote online. And don’t forget about looking for one of our wonderful reps, odds are there is one in your “back yard”. We’ll work with you to find the best pump that will last as long as possible and keep your process running smoothly 24/7/365.