How to safely stop and start circulation
It might not seem like a big deal, but stopping and starting a commercial swimming pool treatment system is dangerous for those unaware of the hazards! In this topic, we’ll go through the issues and discuss a real-life case study where the pool operators gassed several unfortunate swimmers due to procedural errors!
Take a look at the diagram (it can be enlarged) and think about what might happen if the circulation pumps are switched off but the chemical dosing continues.
“Our chemical dosing shuts off when we turn the circulation pumps off – do we need to worry about this?”
You need to at least check that the chemical dosing system has stopped dosing when the pumps have been turned off – don’t assume that the auto-shut-off system will always work. They can and do fail.
- 0:00 Start
- 0:09 Loss of prime
- 2:10 Backflow
- 2:50 Chlorine gas hazard
- 3:44 Stopped circulation hazard
- 4:13 Chemical dosing interlock vulnerability
- 7:54 Distance between chemical injection points
- 8:35 The importance of knowing your system
- 9:08 Restarting circulation system after stoppage
- 10:43 Serious incident at David Lloyd Ipswich
“In the video you mention ‘acid’ chemicals! Why is acid dosed into pool water?”
Good question! It’s all to do with something called pH, which we’ll be discussing later in the course. The most commonly used disinfectants used in the UK are highly alkaline and tend to push the pool water pH levels up past where we need them to be for effective disinfection. So, we add acidic substances to counteract this and stop the pH from going too high.
HAZARD WARNING!
There is a risk of the generation and emission of extremely hazardous chemicals when power to the circulation pumps is cut (intentionally or because of power failure). A system should NEVER be restarted following a failure of the circulation system while there are people in the pool. If there is a concern that there may have been inadvertent mixing of chemicals within the pipework of the circulation system, the fire service should be contacted and the circulation and chemical dosing systems left stopped.
Don’t Forget…
After restarting the system, you will need to ensure chemicals levels are within acceptable ranges by carrying out tests for Free Chlorine, Combined Chlorine, pH, Total Dissolved Solids.
FYI – If you discharge the tested water to waste it is likely the system flow detector will still register there is flow through the testing Cell although it is only draining to waste and will continue to dose chemicals even why the pumps are off ! learned this though experience, so as stated always check your system is not dosing when it shouldn’t
where do i find the information for the drop box of five
Have you watched the video?
If a pool’s plant room is situated beneath the level of the pool is it impossible for it to lose prime?
I suppose it might lose prime if there is a significant breach on the suction side pipework and the system is drawing air in that way. Another possibility is if there is maintenance carried out involving refitting pipework etc.
If you had incident where you were fairly certain that chlorine gas had been created in the pipework, I assume you would evacuate the full building for safety? Or would you take the advise from fire brigade first?
Depends on the circumstances at your particular facility. Evacuating seems appropriate as the Fire Service would not want people in the building while they deal with the situation. Obviously, site staff should not attempt to release any gas themselves.
I have also done this test over and over but the question regarding components in order is incorrect can you assist
Hi Martin,
We’ve made some amendments to the particular question that seemed to be causing some confusion, so you may find it easier now.
Take a look and get back to me if you’re still not able to get past this section.
Kind Regards, Adam.
hello i am having the same issue
Hi there,
There is a schematic and a video under Lesson 3 that explain the pool plant system and order of components well. The video can be found underneath the schematic under a drop-down button “Some tips on how to understand a pool plant system…”