Status of the air valve market in South Africa

Air valves have always played a big role in the South African Water Industry, as Academics have highlighted their importance to Engineers at University and which has had an influence on them at an  early stage in their careers. What also sparked the interest of Users and Engineers was that a new design (called Vent O Mat) came on the South African market with vast improvements on the old “Double Ball” air valves. The manufacturers of this valve went on a marketing spree to convince the market of the extensive benefits of the           Vent O Mat Air valve and the acceptance was great as this valve had obvious advantages. Over the subsequent 20 years Vent O Mat became the Industry standard as Consultants felt “safe” in specifying this valve as it was claimed to have a Non-Slam Anti Surge Closing mechanism. Today most Project designs performed countrywide have the Vent O Mat specified and a feather in the cap of the original designers and marketers. 

At the time when the Vent O Mat ownership of the market was at its highest, A.R.I. (an International Air valve manufacturer), came on the scene and attempted to enter the market. Even though A.R.I. had even at that stage become the world’s leading Air valve manufacturer (with also the most sold units in the SA Agricultural market), the Bulk Water market religiously stuck to its specifications written around Vent O Mat. A.R.I. came to realize that if it wanted to become a serious contender in the SA market it would have to come up with a new design to meet these specifications. After a year of R&D and testing, A.R.I. introduced the model D-060-HFNS, which has a “full bore” orifice and a built-in Non Slam device. As with all their designs, A.R.I. excelled and offered a valve which meets all the SA requirements (with vast benefits over Vent O Mat), and a valve which they viewed as designed especially for South Africa. At the same time they started a Joint Venture company called A.R.I. Flow Control Africa.

The ARI valve has been tested by the various authorities (including DWA, Umgeni Water, Sedibeng Water) and found to solve problem areas including zero maintenance on all applications, and included ARI in their standard Specifications.  A.R.I. have over the last number of years achieved significant market growth.

Since about 2012 the Vent O Mat patent expired and immediately 3 new models became available all claiming different designs to        Vent O Mat, but in actual fact all are based on the same design with small changes. The market immediately accepted these models as they are marketed as Vent O Mat equivalents !!

Since 2012 a new ruling by DTI proclaimed that for all Government projects, of the valves offered there has to be a 70% local content. As with all other decisions by A.R.I. for the SA market, they have promised their full support and have committed to make the A.R.I. valve locally in South Africa.  In terms of A.R.I.’s worldwide turnover where South Africa plays a very small role, this commitment is highly commendable. The locally manufactured range is currently in production and will be available in the next few months.

Now for the Controversial part. 

Despite all the huge benefits offered by A.R.I. air valves, Consulting Engineers still specify Vent O Mat in most of the enquiries and tender documents issued in South Africa. Even some of the Consultants who are known to prefer A.R.I., still enter the Vent O Mat as the preferred product in their specifications !!  What’s going on ?  Surely the South African Engineering fraternity cannot feel so loyal to a South African design that it ignores all the huge benefits of an overseas product ?  Or is it just too easy to keep writing the specifications as they exist on data bases of Engineering Companies instead of making  changes,  and which will take some effort ?

Let’s look again at the benefits of the A.R.I. Air valve


A.R.I. – Zero maintenance. The biggest problem with most air valves in the world is that they start leaking after a short period in the field. A.R.I. has overcome this with a clever seal design, which enables it to offer a 10 year guarantee against seal leakages caused by faulty components. The other advantage of the A.R.I. large seal is that it is always submerged in water whereas the          Vent O Mat sits in an Air gap heated by the sun forming a lethal cocktail of heated Air & Chlorine.  A.R.I. Flow Control Africa never sells spares – and that’s an absolute fact. With Vent O Mat the seals have to be replaced on a regular basis and then it becomes a big process as the long bolts have to be precisely torqued in order to form a proper seal on the flange – that’s a large annual job for any Water Board.

The other problem with leaking seals is that unsupervised maintenance staff simply close the Isolating valve under the air valve when they leak, and then the problem has gone away

In a country where maintenance is often not done, you would think Water Boards and Engineers would embrace a Maintenance- free Air valve. This results in not just a lower Maintenance budget but also less broken pipes and water losses.

Low Pressure Sealing

ARI Air valves seal at a low pressure of 1m, whereas Ventomat seals from only 7m of pressure.  Vent O Mat fit an accessory called a “Bias Mechanism” to improve the low pressure sealing ability, but it decreases the intake ability of the valve (which is the most critical function of any air valve) and you also end up with a Non-Standard air valve.  ARI gives this benefit as standard.

Automatic “small” orifice

A.R.I. uses its patented rolling seal mechanism for the small orifice and which is on average 14 times larger than the Vent O Mat design. It is also self-cleaning, and will seldom block up or “jam”. If one considers that the small orifice works for all the time a pipeline is under pressure and is supposed to prevent build-up of Air pockets and blockages, its function is totally understated and ignored by most Engineers. Is it because Vent O Mat marketing hype has always concentrated on the large orifice as they could do nothing to improve the small orifice performance and are stuck to a size which makes theirs so problematic ? First time users of A.R.I. often comment that the A.R.I. air valve makes a  “hissing” sound at frequent intervals which other air valves don’t. That just proves the point that the Vent O Mat  small orifices are often blocked and not operational, and therefore silent.

Anti-Surge Non-slam large orifice

Vent O Mat came on the market with a built-in secondary orifice, which automatically comes into play when air is driven out the air valve at too high a velocity, and causing “slam” when the water arrives.  Although Air valve manufacturers worldwide have been using other devices like Check valves with bypass holes drilled into them for years, it is convenient to incorporate it into the air valve itself.  The South African Engineers adopted this feature in all their specifications as it provides a “safe” option for Pipeline designs.  What a lot of Engineers experience in practice when commissioning a pipeline is that the Non-Slam feature often restricts the air from being exhausted from the pipeline and causing even greater problems with large areas in the pipeline being still full of air and taking a very long time to exhaust while the pipe is filled. A further “myth” which has been confirmed recently by one of the world’s leaders in Surge Analysis and developer of the Surge 2000 software, is that the Vent O Mat secondary orifice comes into play at a much too high Differential Pressure and “switches” over too late to have any effect on reducing Water Hammer in most applications.

The ARI air valve switches to the Non-slam orifice at a much lower pressure and which has been proven to be the right value by the software programs. The secondary orifce  in the ARI Air valve is external to the Pressure containing body and can easily be removed or changed to a different switch value while the air valve is operational. 


Stainless Steel material

Vent O Mat have always manufactured the valve body in Stainless Steel as it was the cheapest method of manufacture for its design ie a Stainless Steel pipe section as the main body.  This has of course always been marketed as a huge advantage for Corrosion protection. What has not been “marketed” is the fact that the end flanges are mild steel epoxy coated which is easily damaged during assembly of the valve. Corrosion between dissimilar metals has proven to cause serious damage in a very short space of time and resulting in leaking flanges. Is this a case of disinformation marketing where the whole truth is seldom told ?  In the South African context, there is another disadvantage to Stainless Steel components installed in the open or in valve chambers as they simply have too much value and therefore attractive for scrap merchants.

Vent O Mat embarked on a strong marketing campaign against A.R.I. when they entered the SA market and made all sorts of claims that air valves with Ball floats provide huge problems such as “jamming” in the closed position, closing prematurely and with small intake capacity. All these claims have been conclusively disproven by A.R.I. at great expense and with documented proof.  Air valves with Ball Floats as in the A.R.I. design have huge advantages over Solid Plastic floats with little boyuancy.

The South African water industry embraced the Vent O Mat as it provided new technology with improvements over the old designs which were seriously flawed.  Is it not time that these same Engineers had a serious look at the many advantages of the A.R.I. Air valve and get into the new Technology which now presents itself. It may not be a South African design as such, but it is now manufactured in SA and can be called “Proudly South African”.  South Africa has a reputation of  being superior in their design and innovation capability, but this seems to have been lost in the case of Air Valves which play such a significant role in the successful operation of pipelines.  

A.R.I. are the world’s largest manufacturer of Air valves by a large margin and are continuously bringing new technology to the market, including the new Dynamic Model which releases a small amount of water on closing and outperforms any Non-Slam Air valve in overcoming Water Hammer. Vent O Mat has remained stagnant for the last 20 years and are merely using the product as a “Cash Cow”.  Another new A.R.I model which will now be manufactured in South Africa has other unrivalled features which will soon be made public.

Does the South African Water Industry want to go backwards by ignoring these new technologies and not embrace them, and carry on being misinformed with lies or half-truths. Stop being led by marketing “hype” and investigate the claims made by the various manufacturers, and don’t just continue to use outdated specifications. This is the challenge to return to the innovative days when South African Engineers could make claims of being world leaders in Water technology.

The writer would welcome anyone who would like to debate the above and other claims made by the various manufacturers.


Peter Telle











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