HAZARD!
The outlets of a swimming/spa pool can be extremely hazardous!
As well as leaving the pool via the surface water draw-off system, water is also leaving via the sumps (drains). In a traditional swimming pool, these outlets are usually located on the floor of the deep end and are covered with a square grill.
Entrapment hazards
The outlets of a swimming/spa pool are connected to a powerful circulation pumping system. If the outlets are blocked, whatever is causing the blockage will be exposed to the suction force of the circulation pumping system.
The circulation pumps will be sucking on to whatever is causing the blockage, causing a vacuum.
At this point, it will be very difficult to remove the blockage without turning off the circulation pump(s).
If the blockage is in the form of a person, then tragic consequences can occur, including drowning, disembowelment and transanal evisceration, which is where internal organs are forcefully drawn out through the anus.
There are various ways that suction entrapment can be avoided:
- Emergency cut-off devices that automatically turn off the suction pumps when an increase in suction force is detected.
- Multiple outlets being fitted so that even if one of the outlets gets covered, the remaining outlets take the increased water flow and prevent a vacuum being created at the blocked outlet (as below).
- Outlets so that it is impossible to cover them and form a seal. This can be achieved via having the grill surface area of sufficient size (450mm2 is the standard size usually used). It can also be achieved by the use of outlets that are designed to prevent a seal being formed around them when they are covered. These are called anti-vortex drain covers.
- There are also fittings that can be placed over a drain cover that is not an anti-vortex type that will go some way to gaining a similar effect.
- In order to prevent children from getting fingers/toes trapped in the grill, the apertures should be no wider than 8mm.
Once the above design-based precautions have been considered, other precautions can be implemented such as providing training for all relevant staff regarding the dangers of suction entrapment.
See below for some examples of what would have to be considered highly dangerous outlets:
Entanglement hazards
Entanglement hazards are slightly different from entrapment hazards.
They involve hair being drawn into the outlet and then entwining on the other side of the outlet due to the circular motion of the water is it goes through the outlet.
It may be impossible to free the hair from the outlet, even if the circulation pumps are turned off.
People using spa pools are at an increased risk of suction entanglement due to the fact that they will be in close proximity to an outlet no matter where they are situated within the spa pool.
For this reason, people using spa pools should be advised to tie long hair back and refrain from submerging their head under the water.
Staff responsible for supervising the spa pool should be trained sufficiently so that they are aware of the hazards associated with outlets.
The video below provides a brief explanation of some of the hazards associated with pool outlets
Related topics
Hi, I have just watched the video relating to pool drains. I understand the issues around the drains and entrapment but the video relates to USA law. What about the UK, what is the UK law on the use of anti entrapment drain covers?
Hi Louise,
There is no specific law that covers the drain covers, however, the Health and Safety at Work Act 1974 section 3 (It shall be the duty of every employer to conduct his undertaking in such a way as to ensure, so far as is reasonably practicable, that persons not in his employment who may be affected thereby are not thereby exposed to risks to their health or safety.)
and the Management of Health and Safety at Work Regulations 1999, regulation 3 Every employer shall make a suitable and sufficient assessment of (a)the risks to the health and safety of his employees to which they are exposed whilst they are at work; and
(b)the risks to the health and safety of persons not in his employment arising out of or in connection with the conduct by him of his undertaking.
Those 2 regulations cover it really.
struggling with the knowledge test. keep getting 7/8 questions and i think its the arrangement of pool plant components. i believe its the following order: 1. skimmer baskets 2. pumps 3.filters. 4. heat exchanger 5. coagulant injections. can you review the results and guide me please
Hi Warren,
Please revisit lesson 3, Overview of Pool Plant System. There is a schematic there that should be able to help you.
Ive used the schematic but still seems to be incorrect. Possible to contact you over the phone?
Hi Warren,
I hope the chat with Adam answered some of your questions. If you have any other questions, please don’t hesitate to call again.
I have taken knowledge test 4 over 15 times. Every time I get 7/8 questions correct. The only question I could be getting wrong is the one that requires plant room components be placed in the correct order including sample line out and sample line return. I am very confused as I have followed all diagrams of these components based on the diagrams included in this section and it still appears to be wrong. Is it possible that the diagrams are labeled or placed incorrectly? I have tried reordering these components in everyway possible according to the diagrams you have provided.
Hi Phil,
Try putting the sample line return as the first component. Sometimes the sample line return doesn’t actually ‘return’ but is positioned such that sample line water goes to waste. However, for the purposes of this course, you are to assume that the sample line does return to the main system pipework. In this case, the sample line would typically return to the suction side of the system (not the delivery side).