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WilliamRowleyAn Interview by Eric Herman

For more than 30 years, Dr. William N. Rowley — founder and principle of Rowley International, headquartered in Palos Verdes Estates, Calif. — has worked tirelessly to address the causes of suction entrapment incidents. He has personally investigated scores of cases, has served as an expert witness in numerous resulting lawsuits and has conducted multiple research projects studying these often-horrific events.

By applying what he’s learned in his work designing commercial pools and aquatic facilities the world over, Dr. Rowley has devised systems that are as safe as possible. The result? Of the literally millions of people who have immersed themselves in pools he has designed, not one has ever been the victim of entrapment.

Now, as the effects of the Virginia Graeme Baker Pool & Spa Safety Act (VGB Act) are being felt throughout the aquatic realm, we checked in with Dr. Rowley for some historical perspective and his take on where the industry stands in trying to eliminate suction entrapment accidents.

When you first looked at this problem back in the 1970s, what did you learn about suction entrapment in your initial rounds of investigation and testing?

Back in those days, I was working with SwimQuip, one of the industry’s leading pool-and-spa equipment manufacturers at the time. We were already working on some health code revisions when we were contacted by officials at the International Association of Plumbing & Mechanical Officials. There had been a suction-entrapment drowning death — a child in Orange County — and they were trying to figure out exactly what had happened.

We investigated the accident and started doing some calculations based on biometrics and modeling. We came to the conclusion that we needed to study the issue using a live model. That was the first time I volunteered to use my own body for the purpose. We immediately discovered that under all the conditions we tested — including various flow rates and types of outlet fittings — if the cover or grate was properly attached and intact, I could easily free myself simply by rolling off the grate. I did so with very little effort; I didn’t even use my arms or legs for leverage.

Why is this issue so confounding for so many people?

It should be fairly simple, really, because we know how to prevent suction entrapment with proper flow rates, secure fittings and split drains. Or with no drains at all. The reason it’s seemingly so complicated is because there are so many people involved on so many levels. And some of them are primarily concerned with selling products, so they may see the safety issue as secondary.

That’s a tough charge.

It is. And of course, no one wants to appear to be callous when it comes to safety. But when you’re in the trenches on this issue as I have been all these many years, and you watch the behavior of some of those involved, you can’t come to any other conclusion: They’re really only there to use this incredibly serious issue as a way to gain an advantageous position in the marketplace.

Can you be more specific?

Let’s look at the manufacturers of suction vacuum-release systems (SVRS). I’ve been at odds with a handful of representatives of these companies for years because of the way they market their products.

We know those devices won’t stop limb entrapment accidents because by the time they work, the victim’s arm or leg is already lodged in the plumbing.

They don’t stop hair entanglements, either. This is the most common type of entrapment accident in the presence of SVRS systems. The flow is never completely blocked, so these devices don’t “know” to turn off the system. Moreover, they won’t work on large commercial systems because the suction forces are too great. And being mechanical, there’s always a chance of failure — especially if the device is not maintained or calibrated properly.

And finally, they do not stop eviscerations. These accidents, which involve tearing of the lower intestine or colon, happen almost instantaneously. Because of the dynamics of hydraulic systems, SVRS devices simply cannot react in time to prevent these terrible accidents. (For the record, manufacturers of these devices do not claim that their systems will prevent eviscerations.)

Thus, of the four identified types of entrapment accidents, the SVRS systems do not prevent three of them.

Are there situations where one of these devices might save someone? Absolutely, and I’ve never said they have no use. But we need to be realistic about the narrow range of situations in which these devices can be effective — and that’s not how these companies have positioned their products.

You’ve been a proponent of split main drains. Why?

As far as we know, there’s never been any kind of suction entrapment incident on a properly functioning, code-compliant, split main drain. I’m not saying that there isn’t some extreme condition or unusual circumstance where it couldn’t happen, but there’s no documented case of which I’m aware.

No matter whether you look at it from an engineering standpoint or just plain common sense, it’s obvious that split drains reduce the risk to such infinitesimally small levels that they can be considered an effective method of prevention.

When you combine proper flow rates with secure, code-compliant grates or covers, you’ve effectively solved the problem.

Then why do some argue against their use?

Maybe it’s because they remove the need for an SVRS device or relegate it to a purely secondary measure. The people who make those devices don’t want to hear that — or for others to start to see it that way.

One of the terms that comes up in VGB rules and in recommendations by organizations such as the U.S. Consumer Products Safety Commission is “unblockable drain.” What exactly does that mean?

When the American Society of Mechanical Engineers and the American National Standards Institute were working on their standards, they came up with what is known as the 99-percentile man — meaning human dimensions that are equal to or bigger than 99 percent of all people. That fellow is 75.6 inches tall and weighs 244 pounds. In their testing using models, it was determined that he could block a drain that is 18 inches wide and 23 inches tall.

Unfortunately, they didn’t do any human testing, which I’m certain would have dramatically influenced the findings because of the way the human body moves when it’s stuck. We don’t pull ourselves straight off, but instead roll off. When you break the suction on one side, you basically peel off the drain like a postage stamp. As a result, I would say that the resulting codes are much harsher than they need to be because they don’t take into account the supple and flexible nature of the human body.

Again, when you perform tests with live subjects, you immediately learn that if the grate or drain cover is in place, you can roll right off. It doesn’t matter if it’s an antivortex cover or a basic grate: If it’s intact and securely attached, you will be able to free yourself.

Overall, has the VGB Act helped or been a step backwards?

I think it’s helped because it has forced everyone down the line — from health inspectors to contractors and end users — to take a serious look at the problem and in many cases correct potentially hazardous situations. Specifically, a number of non-compliant grates that might potentially have been hazardous have been replaced.

As with anything the government produces, the language can be confusing and even contradictory, so it has its problems.

Ironically, the actual accident that prompted the act in the first place occurred in a residential spa, which is where the vast majority of suction entrapment accidents happen. Despite that fact, the law addresses commercial installations only, so it doesn’t even address residential pools or spas.

Still, I think the measure has been helpful.

In your opinion, what’s the ultimate solution to the problem?

The most effective measure is one that is not accepted or even considered by most health department officials: It’s time that we start eliminating main drains altogether in pools and spas, both commercial and residential.

This is a classic case of tradition trumping common sense. Pools can function perfectly well without main drains — which really aren’t even drains at all, but really are just bottom suction outlets. Pools are normally drained using sump pumps, not their drains. And it’s been shown time and again that main drains are not necessary for proper circulation. (Consider also that aboveground pools have never used main drains and operate without problems.)

From my own experience in designing commercial pools for all types of applications, I know that they function beautifully without main drains. In many systems, we’re now using floor inlets that do a wonderful of job of dispersing chemicals and enhancing energy efficiency for heating. So why not simply eliminate the risk by eliminating the place where suction entrapment occurs: on the main drain.

If you look at it from a risk-analysis standpoint, risk is exposure times the hazard. In this case, the hazard is the drain itself; if you remove it altogether, you’ve eliminated the risk. The reason spas are riskier is that the exposure is greater because bathers are closer to the drain. So again, eliminate the main drain and place the suction outlets in skimmers and gutters where they pose virtually no risk. Then the problem goes away.

Are there other advantages to eliminating main drains?

By eliminating main drains, you also eliminate the cost of installing them in the first place. That may not amount to much in a residential pool or spa, but in a 50-meter competition pool, a drain can cost upwards of $50,000. In addition, you eliminate the cost of remodeling them. We’re finding that many facilities with large pools simply do not have the wherewithal to remodel their pools into compliance, so they face closing down. That whole set of problems goes away when you eliminate the drain.

Compounding the problem is that health departments have never thought about these issues in this way before and are notoriously slow in changing directions. Despite the resistance, there is absolutely no downside to eliminating main drains and everything to gain.

Considering all the years of controversy, research and tragedy, what you’re suggesting seems almost too simple a solution.

In my opinion, this problem has never been as complex as it’s been made out to be. When you participate in lawsuits as an expert witness, you learn just how convoluted it can become when skilled attorneys get hold of this issue. But that doesn’t change the laws of physics — and in this case, nobody can deny that you cannot get stuck on a drain that does not exist.

If we’re truly serious about eliminating suction entrapment, we have to get rid of single-suction main drains, period. They can be dangerous and are obsolete. Until we do so, I’m afraid this issue will continue to be with us to some degree, no matter how much the current crop of regulations, standards and recommendations help.

When we do decide to get rid of main drains, we’ll say goodbye to suction entrapment once and for all. That is probably easier said than done, but it’s entirely possible and, I believe, necessary in technical, ethical and even moral terms.

Dr. William N. Rowley , Founder and Chairman of the Board of Rowley International Inc., has been directly responsible for the design of over 600 major swimming pool complexes worldwide. A registered and licensed Professional Engineer (PE) in the State of California, the District of Columbia, and 27 other states, Dr. Rowley is a Certified Safety Professional (CSP), as well as a licensed California General Engineering Contractor, a California General Plumbing Contractor and a California General Solar Contractor. For more information, go to

Eric Herman is the editor of WaterShapes.

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  • Guest - Paul Pennington

    In the Watershapes EXTRA interview titled “The Ultimate Solution for Suction Entrapment,” William Rowley references his personal experiences related to body-entrapment testing that he has conducted over the years. He stated that if the cover or grate was properly attached and intact, he could easily free himself simply by rolling off the grate. The vast majority of entrapment cases involve children ranging in age from 3 to 14 years of age. These are victims who do not have the presence of mind or the physical capacity of an adult, and therefore are not able to free themselves “by rolling off the grate.” The Virginia Graeme Baker Pool & Spa Safety Act was named for a child, age 7, who was entrapped on a spa drain that had a suction outlet cover securely in place.

    The May 24, 2010, Consumer Product Safety Commission (CPSC) Entrapment Report cites 94 reported pool, spa and whirlpool cases of circulation/suction entrapment in the United States from 1999 to 2009. This same report states that 33 cases were related to body entrapment and 32 cases were classified as limb entrapments. We know of only one U.S. limb-entrapment case where the arm of a small child was reported to be mechanically stuck in a vacuum line. This incident took place in Miami and was well documented by all of the major news agencies. Fortunately this child survived. All other known U.S. limb-entrapment cases have reported release of the bather once the suction force was released. Given this understanding, suction entrapments (body and limb) accounted for 69% of all incidents of entrapment injury reported by CPSC for the period from 1999 through 2009, and 58% of the reported fatalities.

    Vacuum-release technologies are characterized by Rowley as limited to the mitigation of body entrapment, implying that vacuum-release technology is only effective in one out of four or five cases. The vast majority of limb entrapments are suction-force related, and when added to the reported body suction-entrapment cases, these cases represent the vast majority of the recent circulation system injuries and fatalities noted in the CPSC Entrapment Report. Additionally, research funded by NASA through the Space Alliance Technology Outreach Program (SATOP) in conjunction with the Pool Safety Council shows that vacuum-release technology would be effective in mitigating limb entrapment. A second report also shows that the same vacuum-release technology can mitigate evisceration in most cases.

    Rowley further states that there have been no known cases of entrapments on dual or split drains. What is not mentioned is that there have been entrapments on dual drain systems where only one of the drains was functioning, or where the drains appeared to be multiple outlets but were in fact single outlets plumbed to an individual pump. The other factor relevant to dual or split drains is the reality of dynamic hold-down forces. If improperly constructed, dual-drain systems can present a serious danger of entrapment for younger bathers. This can happen when flow rates are high, sumps and connector piping are improperly fitted and sized, and suction outlet covers are of the low profile/low open area type. If a bather should block one of the dual outlets, with all flow coming from the second outlet, a dynamic hold-down force is created that can be hazardous — up to 200 pounds’ force in some cases.

    The CPSC incident report supports the safety prescription of installing a certified anti-entrapment cover along with a vacuum-release or vacuum-limiting system as a reliable and safe method to avoid all types of entrapment injuries.

    Paul Pennington, Chairman and Founder
    Pool Safety Council
    Washington, D.C.

  • Guest - Skip Phillips

    It was a pleasure to read Dr. Bill Rowley's observations in your recent issue. His common sense, objective and realistic approach is refreshing, especially in light of the self-serving posturing we see so often on the entrapment topic.

    Frankly, the unwillingness of the entire pool and spa industry, including the various representative trade associations, to take a hard stance on line velocity and suction grate issues has exacerbated the problem. Some of the worst pool builders in the country, ones that historically hide behind false credentials and so-called design awards, continue to have a position of credibility.

    Low line velocities and multiple grates, simple approaches, would have no doubt eliminated most, if not all, of the horrific tragedies to which the owners of our products have been subjected. Unfortunately, we are now obliged to allow the government to take charge of the issue, forcing hideous grates on our clients, and in many cases dodging the original line velocity culprit.

    Reducing line velocity makes sense on so many levels, it's hard to understand the reluctance of our industry to embrace the concept. Not only is safety enhanced, but the vast improvement of efficiency and lower decibel operating levels would make sense completely independent of the safety concerns.

    While I'm sure you will get a "push back" from parties interested in a different approach for any number of reasons, Genesis 3 in general, and Questar in particular, applaud WaterShapes and Dr. Rowley in taking the road less traveled. For those who do not know, that would be the high road.

    Skip Phillips
    Questar Pools & Spas

  • Guest - Diane Carlson

    Sounds like a simple solution to a difficult problem which would initially only require plugging the main drain until such time as the pool is remodeled. [This] could go a long way in getting the existing residential market free of the entrapment hazard. But I would like to hear more about the hydraulics involved to achieve circulation in existing older pools with 1.5" plumbing.

    Diane Carlson
    SkyBlue Pool Supply

  • Guest - William Giffin

    Does the Uniform Plumbing Code mandate main drains in swimming pools? I think the nomenclature of the term "main drain" is what causes the confusion. In the pre-1970 days, many residential pools were equipped with dedicated pipe and valve to isolate the "suction inlet" that allowed draining a pool with the filter system. In most pools today, the "main drain" is simply an equalizer line to the skimmer. I don’t know how many times in my 30-plus years in business I’ve been asked, “How do I open the drain?" The static pipe of todays "main drain" could be easily eliminated if you could just break old ideas.

    William Giffin
    Power It Free Solar Solutions

  • Guest - David Sisson

    Eliminating the main drain might have an adverse effect on circulation; adequate circulation aids in keeping the water clean and sanitary. So in my mind the questions are: What is the measure of adequate circulation? What are the standards and how can those standards be measured? For instance, is there some standard of measure for dirt in suspension in pool water? Adequate circulation in a pool would call for a certain measure for cleanliness, or how much dirt in suspension is acceptable? There should be some type of testing done regarding effective circulation. If pool water can be circulated effectively without the use of a main drain, then elimination is an easy resolution to the problem.

    David Sisson
    American Pool Care Inc.

  • Guest - Bruce Carlson

    Being a pool builder for over 15 years, I have yet to experience any suction entrapment issues, as I have I always used two (main) drains (for pool/spa and for waterfeature suction sources) set 3 feet apart (at a minimum), with properly installed drain covers. However the idea of no pool main drains is completely feasible as I have found main drains (for the pool) to be of no significant use. A simple test of pool dual main-drain functions [proves] that not even [with] a simple brush of debris towards a drain, we will not see any of the debris "sucked" into the drains.

    However, the floor drain design lends itself to being helpful to pool service people who want an additional source to drain a pool quicker for maintenance reasons (providing the plumbing and valves are properly configured to provide this option). But that is typically overcome by the use of stand-alone discharge pumps, which are more commonly used.

    Which brings up the question of how best to configure a spa for proper flow and drainage needs. We have placed the drains on the calf portion of the spa seats, and that seems to work well (provided the room is available). However, cleaning a spa is much easier if we have floor drains, as the circulation of a spa is greater than that of a pool. These drains will collect the debris easier, [yet] still not of the force to be considered hazardous. This issue is still on our minds as we try to develop a better means to build and circulate spas and make them as safe as possible.

    Waterfeatures do need a source for their particular flow needs, and we have always used dual drains (even triple), set 3’+ apart on the wall of a pool in 4' deep water or greater. Standing beside these drains, no significant suction was encountered (when using the proper drain covers, as always). Additional skimmers would sometimes help for waterfeature suction needs; however, smaller debris that gets into these skimmers will find its way back to the circulation of these features, thus creating another maintenance issue. So this procedure has its pros and cons.

    Bruce Carlson

  • Guest - Valentino Carli

    I started in pool service and have always removed the float valve on single main drain pools. I tell the customer to watch the water level or suffer pump burnout. It is better than having the float close and draw water only from the main drain. Since I have been building pools I always use dual drains and dual skimmers — the more suction points, the better. When will common sense rule?

    Valentino Carli
    Pacific Breeze Pools

  • Guest - Anonymous response

    I have been in the pool construction business for 34 years. My brother used to draw plans for Dr. Rowley when he lived in Palos Verdes. From my experience, having built pools with separate main drains and ones that were tied into the skimmer, the difference in water turnover and clearing a cloudy pool was night and day. A separate main drain would clear the water up twice as fast or faster than a drain tied into the skimmer. For Dr. Rowley to say that an aboveground pool with no main drain is just as good as an inground pool with a main drain destroys any hydraulic credibility he thinks he has. Several split-suction inlets with properly installed drain covers seems to me a reasonable solution to this problem.


  • Guest - Dave Kaelin

    I think eliminating main drains is a good idea. It dispenses with a lot of regulation and possible future liability. I personally know of a local pool builder who already has adopted this method and has been doing [it] for years now. Alternatively, main drains do have a purpose. Consider a drop in water level below a skimmer. The main drain allows for some flow through the pump, thereby not damaging it. However, a water leveler should negate the issue.

    Dave Kaelin
    Grant Pools, Inc.

  • Guest - Rex Richard

    Dr. Rowley is highly respected and his contributions are clearly noted, but the facts are misplaced. First, entrapment has been identified and broadened to include five forms of entrapment; "full body" entrapment that Dr. Rowley addresses is only one of the five. In light of the other four, there are many issues that make the use of duel drains in some cases a doubling of the problem. Also, much testing has gone into the idea of a properly designed single drain, and it in fact is as safe if not safer than a duel drain system, but we are all fighting emotions not facts.

    The facts [are that] going back to the 1930s when pools were designed with great care and built by engineers, the specifications for pools stated that "drains should be disabled when swimmers are present in the pool." It was known then, as tests have re-established recently, that drains provide an outlet for water but have no contribution to circulation. The water under pressure from the inlets is what "circulates" the pool and distributes chemicals.

    In light of all recent discoveries, a proper drain design would, in fact, fix the problem — but the problem exists because we have drains at all. There is no need for a drain in a pool. They were originally provided due to the "fill and draw" method many of the early pools used and as a way to empty the pool for maintenance. They were never intended to operate while swimmers were in the pool.

    Somewhere along the way, some builder probably figured it was cheaper to use that already-existing drain plumbing as an outlet, thus reducing one additional plumbing run to the pool. This same thinking was used to further reduce costs by later eliminating the drain plumbing back to the filter and instead routing it through the skimmer. Our industry often holds ideas that were founded originally as ways to reduce costs, not improve performance. The fact is, every pipe opening in the pool — whether suction, return or equalizer — is a potential danger if it is of sufficient diameter that a child can have a limb entrapped.

    We can easily fix this problem for good by the elimination of all drains. In fact, a proper "overflow" design (think skimmers not perimeter overflow) will circulate, skim and clean the pool better. By the elimination of drains, there is no loss whatsoever in circulation; in reality, there is an improvement. In addition, we should be looking at ways to reduce all pipe penetrations in diameter or provide a way to protect them from a child inserting an arm into the pipe.

    Not addressed at all by the single-drain versus dual-drain argument are the mechanical, limb and hair entrapment issues. The very presence of a second drain actually doubles the risk in these forms of entrapment.

    We really need to stop the emotional and profit-driven arguments supporting drains at all. It is time we learn from the past; embrace the best, more-recent science; and eliminate the drains entirely.

    Let's ask ourselves the question: “How concerned are we really about safety?" Those who fail to learn history will fail to benefit from its lessons. Let’s fix this and get it right this time. The issue is not one or two or six drains. All of them can be made safe — but the better issue is, why do we have them? They are not needed.

    Rex Richard
    Pool Genius Network