Shutdown, start-up & commissioning
Idle towers and new systems carry their own risks. We plan shutdowns properly, bring systems back safely and commission new plant so it starts life under control.
Standing water is where the trouble starts.
A cooling tower that's sitting idle with water in it is a problem waiting to happen. With no circulation and no dosing, biocide levels fall away and bacteria get going. Then the day it's switched back on, it can throw the lot out as drift.
For short idle periods the usual answer is to keep water circulating with treatment running. For longer shutdowns, the system is normally drained, cleaned and left dry, then cleaned and disinfected again before it comes back into service. Your risk assessment and written scheme should spell out which applies, and we'll help you follow it.
New towers and refurbished systems need commissioning too. HSG274 Part 1 expects new systems to be cleaned and disinfected before they're put into use, with treatment and monitoring in place from day one. See our cleaning and disinfection page for how we go about it.
Planned shutdown
Drain down or keep circulating, depending on how long it'll be idle and what your risk assessment says.
Start-up after idle periods
Cleaning and disinfection where needed, refill, treatment established and checks before full load.
Commissioning of new plant
Pre-commission clean and disinfection, dosing set up, baseline samples and records opened.
Seasonal systems
Towers that only run in summer, planned around the start and end of the season.
Notification reminders
New towers need notifying to the local authority; decommissioned ones need notifying too.
Records for the log book
What was done, when, and the follow-up monitoring results.
Shutdown, start-up & commissioning: common questions
How long can a cooling tower sit idle before it's a problem?
There's no single safe number. Stagnant water quickly loses its biocide reserve, so even a few days without circulation can matter. Your written scheme should say what happens for short and long idle periods. If it doesn't, we'd recommend getting that added.
Do we need to disinfect before restarting?
After an extended shutdown, HSG274 Part 1 expects the system to be cleaned and disinfected before it goes back into service. For short breaks with treatment maintained, a check of chemical levels and a dip slide may be enough. We'll advise based on your system.
We're installing a new tower. When should you get involved?
As early as you can. We can advise on dosing points, sample points and access for cleaning before it's built, then commission it with a clean, disinfection and baseline sampling.
Does a new tower need notifying?
Yes. The Notification of Cooling Towers and Evaporative Condensers Regulations 1992 require you to notify the local authority in writing. You also need to tell them if a notified tower or condenser is taken out of use for good.
Related services
Related articles
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Bringing a cooling tower back into service after a shutdown
Restarting an idle cooling tower? Why stagnant water is a Legionella risk, what HSG274 Part 1 expects before restart and a practical start-up sequence.
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Do you need to notify the council about your cooling tower?
The Notification of Cooling Towers and Evaporative Condensers Regulations 1992 explained: who notifies, what to send and when to update it.
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How often should a cooling tower be cleaned and disinfected?
HSG274 Part 1 says at least twice a year, but some towers need more. What the guidance expects, how a clean works and the signs yours is overdue.
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