Type21 Series couplings are the most widely used industrial couplings in the world and are used by more professionals in a variety of industries than any other coupling (well according to the firm that invented this series anyway!). The reason for this is that they are compact, very easy to use and are generally reliable. They are also relatively inexpensive when compared to many other professional coupling series.
Having spoken to several manufacturers of these items they all agree that the window cleaning industry provides one of the harshest life-cycles for these products than any other industry. This is because of the constant coupling and uncoupling, use in dirty environments and also being dragged and dropped repeatedly through each day's use.
One issue that does arise is that because they are such a common coupling they are made in many different factories around the world to varying standards. These inferior versions can sometimes find their way into the supply stream of many mainstream coupling suppliers (which is why we have our ones supplied direct from factory).
When a female coupling fails very quickly upon changing, the reason is usually down to the male side of the coupling. What happens with age and use is that the male coupling plug gradually becomes damaged and slightly misshapen. Over time this will damage the female coupling and eventually leads to the failure of the coupling. A new female coupling is then often purchased and fitted and works well for a short while until it then suddenly fails and the quality of the female coupling is called into question. What has actually often happened is that the (unchanged) male coupling plug has very quickly rendered the female unusable. This is sometimes something as simple as jamming the female in the open position which can be rectified by pulling back the collar on the female coupling. However often the damage caused by the male is permanent and can only be remedied by replacing the female. It is for this reason that we (and most manufacturers) recommend changing the male plugs at the same time as replacing the female couplings.
Another common reason for either premature coupling failure or jamming open is that the male plug is inserted with dirt/grit on it or with dirt/grit in the female. This will have the effect of opening the female coupling valve without allowing the male plug to lock in place. If pulling the collar back does not cure this then cleaning the male coupling off and re-inserting it into the female will disengage the open valve. I often will have to blow dirt/grit out of the female coupling before use depending on the work environment that I have been in.
I have personally used these connectors for about 7/8 years and usually anticipate getting about 5-7 months from a female coupling before needing to replace - however this is dependant upon using the coupling with at least one Protecta-Ball fitted to the male plug side. I also have several reels with another Protecta-Ball fitted on the female side for even greater protection. This does protect the couplings whether connected or apart from much damage incurred on the ground. There are alternatives that can be used that have the same effect.
We made the change in supply a while back from the type with an end-circlip as we had some reliability problems with the circlip popping off during use. Based on our own trials we found the current version (without circlip) outlasted the old ones on average.
Alternatives
Hozelock type -I personally used these for several years, but found that they broke easily (especially when run over!) and when they become worn they would often jam with the male inserted - causing much frustration on my part.
Series 026 Type - These are a very robust couplings and have a very good flow-through rate. Being larger they can be tougher, but are slightly harder to operate and are more bulky. They are also prone to the same issues as the Type21 Series if the male plug becomes damaged. I personally do not use these because they are larger, heavier and harder to operate.
