Are Pool Drains Dangerous?
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Are pool drains dangerous? In a word, yes. Now I do not want to cause alarm with pool owners and swimmers since the vast majority of pool drains pose no risk to bathers, but the reality is that pool main drains can be dangerous. The scope of this article that you are reading is intended to inform you about the potential risks from pool floor drains, but also to give you insight as to how main drains are (supposed to be) installed to prevent these risks.
One of the most concerning aspects of pool floor drains is the fact that there are many different ways (configurations) in which they can be installed. Some plumbing configurations have more potential for danger than others, and for this reason it is important to learn as much about your pool and your plumbing system as possible.
There are a lot of people who claim to have an irrational fear of pool drains. This may be partially from Hollywood movies showing death and drowning due to pools drains, but it could also be due to the fact that there is some truth to the danger. Add to this the very macabre nature of pool drain accidents and you have all of the requisite requirements for full-on phobia development. While it is true that pool drains have the potential to be dangerous, they are not dangerous in the way that irrational fears may portray the danger. For example, you will not get sucked into a pool drain simply by swimming in close proximity to it. There is no discernable sucking power from a pool floor drain - even one that is installed in the most "dangerous" possible plumbing configuration. Simply swimming near a main drain poses no concern for entrapment.
What is so dangerous about pool drains? - If a main drain were to become covered completely, this can create a vacuum effect because the pump is still attempting to pull water through the pipe. The amount of vacuum force that an average pool pump can generate is FAR greater than what a swimmer can resist by pulling themselves away if they cover the main drain completely with their body. This is why there have been changes in the swimming pool industry to how main drains should be installed, specifically to avoid (or at least reduce) the potential for entrapment hazards. However, even if the pool pump is not running, it is possible that a swimmer could get their fingers or hair stuck in a main drain lid. This is why it is so important to keep main drain covers in place at all times, and cracked or broken main drain covers should be replaced.
Active VS. Passive Main Drains - The different plumbing configurations for main drains pose different levels of risk to swimmers. The "most dangerous" plumbing configuration is an active suction system where there is a single suction main drain connected via a single pipe directly to a pool pump. This is the most likely installation style to result in an entrapment. A passive main drain plumbing configuration is safer than an active suction system since in a passive system the main drain is only used as a non-pressurized equalizer line to the bottom of the pool skimmer. This allows water into the skimmer even if the water level in the pool falls slightly below the mouth of the skimmer opening. In a passive main drain there is zero suction from the pump since the skimmer is open to air through the skimmer lid (not closed loop). In an active main drain there is direct suction from the pump to the main drain, without any other openings (closed loop). If you want to determine how safe (or dangerous) your pool main drains are then you need to know whether the pump sucks directly from the main drain (active), or whether the pump only draws from the skimmer and the main drain supplies a non-pressure equalizer line to the skimmer (passive).
Do You Need A Main Drain In A Swimming Pool?
Many pool owners, aware of the potential danger of pool main drains, ask the question "do you need a main drain in a swimming pool?". There is some common misinformation circulating on the internet that leads pool owners to believe that they do not need a main drain in their pool. The reality is that most pools should have a main drain, and many pools must have a main drain in order to function properly. Actually, of all of the different types of swimming pools, it is only vinyl liner pools that really have the option of no main drain. Both concrete pools and fiberglass pools must have a main drain in order to have a place to install the hydrostatic relief valve. Vinyl pools not needing protection against hydrostatic pressure can potentially delete their main drain with the only concern being the compromised filtration and circulation of the pool water.
A swimming pool filtration system should include a skimmer suction point as well as a deep end floor suction point. This allows for maximum flow control, filtration and heat efficiency in the pool, as well as helping to minimize on the amount of dirt and debris that collects on the floor of the pool. The concept that swimming pools do not need main drains comes from the fact that main drain pipes are hard to fix when they break, and as a result many pools have the main drain lines decommissioned and sealed on both ends. These pools are still able to operate and stay clean...so everything is good right? Not so fast. Sure the pool is still operating, but that does not mean that the pool is operating efficiently, or at least as efficiently as it could be. Just because some pools can limp along and get by with the main drain deleted does not mean that deleting the main drain in your pool is a good idea. Much more common (and practical) than deleting your main drain might be altering the main drain (decommissioning) so that it is still there, but is not actively connected to the pump. This way concrete and fiberglass pools can still have a place for the hydrostatic relief valve, but by plugging the suction line the pump no longer draws water from the main drain. Again, this compromises the filtration system and efficiency of your pool, but if you are dead set on deleting your main drain, then decommissioning the plumbing by plugging the pipe might be a better option than deleting it altogether.
How Do You Delete A Pool Drain?
If you have a vinyl liner swimming pool it is possible to delete the main drain completely when the liner is replaced. This usually would involve plugging the pipe in the main drain before filling the main drain with concrete. The final step to delete the main drain is to simply install the new liner and do not install the main drain flange and cover. This is the only way, and only potential situation, where you can delete a main drain completely. For all other pool types, and for vinyl liner pools not currently needing a new liner, you can not delete a main drain completely but you can decommission it by disconnecting it from the plumbing system (or plugging it).Almost all pool main drains can potentially be plugged or disconnected from the plumbing system. While not ideal for the filtration efficiency and flow efficiency of the plumbing system, this does reduce the potential for danger due to entrapment. For many pools, such as concrete or fiberglass pools, you can not delete the main drain because you need somewhere in the floor of the pool to install a hydrostatic relief valve. You can however delete the suction pipe such that the main drain no longer is connected to the pool pump, but instead only sits dormant as a fixture to hold the hydrostatic relief valve. Without any suction present in the main drain whatsoever, the only risk then becomes someone physically becoming stuck to the main drain with their hair or fingers.
Even without flow or suction from the filtration system, it is still possible that a swimmer could get their fingers, toes or hair caught in a main drain lid. This is why main drain lids are (now) designed with safety as the paramount concern. Modern day main drain lids are designed to eliminate the potential for someone to get their appendages stuck in them, and with no water flow there is little risk for swimmers hair to get pulled in and stuck through the main drain cover openings. Even with a perfectly designed and installed system, things can still break, and this is why no pool drain can ever be said to be 100% safe.
Dual Main Drains VS. Single Suction Main Drains
Modern day swimming pools use a dual suction point system for installation of active main drains. In these systems each main drain is installed a minimum of three feet apart, and the main drain lines are connected together. In this instance you would need to cover both main drains in order to create an entrapment hazard from the vacuum power of the pump. While this style of installation is clearly better than single suction main drains, this is still far from a perfect system. What is stopping two swimmers from blocking both main drains at the same time and creating an entrapment hazard for both of them? In short, not a lot.
Dual main drain suction points are certainly better than single point suction drains, but it would be an overstatement to call this configuration safe. Since it would only take two bodies instead of one to cover the drains, another layer of protection built into modern day pools is the use of VGB Virginia Greame Baker Act compliant drain covers. In addition to these covers having no accessible spots where swimmers can get their fingers or toes stuck, these lids also have curvature and flow hole placement such that it would be specifically difficult to block the entire flow to the cover. Still, even with hard-to-block VGB compliant drain covers, as well as dual suction point plumbing configurations, you can not say that pool main drains are 100% safe.
Dual main drains are certainly superior to single suction main drains in terms of reducing the risk of an entrapment in the pool, and while it can not be said that this solves the concern for risk completely, you should upgrade to dual main drains the next time your pool is renovated. If you have a vinyl liner pool then this is the only type of pool that you can conceivably delete the main drain on entirely. This does compromise the efficiency of the pool filtration system and you should look into having the main drains split into dual suction points instead of deleting the drain. All commercial swimming pools, all concrete pools and all fiberglass pools have main drains...there is no reason why vinyl pools can get away without them other than it is easier and cheaper to delete a main drain than to upgrade it to a dual suction point.
The only other solution to the danger of the main drains in your pool is to upgrade your pump to an SVRS model. SVRS stands for "safety vacuum release system" and these pumps are designed to immediately turn themselves off in the event an entrapment. These pumps detect a sudden increase in the restriction to flow of the system and turn off. Unfortunately SVRS pumps do not work on every pool installation as there are technical limitations on how the release system works. Things like in-floor cleaning systems and solar heater installations can cause variances in the pressure of the plumbing system, which in turn causes a lot of false alarm shut-down situations with SVRS pumps. Still, most pool systems can accomodate SVRS pumps, and if you area really worried about entrapment and the main drains in your pool then perhaps an SVRS pump is a good investment for your pool
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Swimming Pool Steve is an award winning, second generation swimming pool specialist from Ontario Canada and one of the most trusted voices in the swimming pool industry. With over 20,000,000 views on the Swimming Pool Steve YouTube Channel, winner of the Pleatco Pool & Spa Industry Leadership award and author of hundreds of pool and spa articles both online and in print. Steve is committed to helping pool and spa owners as well as pool and spa industry workers learn more about the technical side of building, renovating, repairing and maintaining all types of swimming pools and spas. Follow Swimming Pool Steve on Facebook, Twitter and YouTube.
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