Ross Wakelin
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Reproduced from the MCDEM site.....

 

Not all bleaches are safe to use in stored drinking water

 

The Ministry of Civil Defence & Emergency Management has reviewed its advice about storing water for emergencies and has issued new, additional information.

 

The Director of Civil Defence Emergency management, John Hamilton, said the Ministry’s advice has been to add household bleach to stored water. That should still be done. However, with new products coming onto the market not all bleaches are safe to use in drinking water.

 

It is not safe to use bleaches that contain added scent or perfume, surfactants or other additives - they can make people sick. Surfactants will make the water foam or bubble when it is shaken or mixed. If the product's label is not clear about what has been added to the bleach, do not use the product for the safe storage of water.

 

Instructions for safely storing water

  • Wash bottles thoroughly in hot water.
  • Fill each bottle with tap water until it overflows.
  • Add five drops of plain, household bleach per litre of water (or half a teaspoon for 10 litres) and put in storage. Do not drink for at least 30 minutes after disinfecting.
  • Do not use bleaches that contain added scent or perfume, surfactants or other additives - they can make people sick.
  • Label each bottle with dates showing when the bottles were filled and when they need to be refilled.
  • Check the bottles every 12 months. If the water is not clear, throw it out and refill clean bottles with clean water and bleach.
  • Store bottles away from direct sunlight in a cool dark place. Keep them in two separate places and where there is not likely to be flooding.

 

Mr Hamilton said the new advice came about after a member of the public asked the Ministry if bleach that included a surfactant could be used in stored, drinking water. 

 

“We contacted a manufacturer of bleach and the Ministry of Health, both of whom willingly provided the information we needed to write new advice for the public.”

Ross Wakelin
Hits: 463

Recently I was asked how to ensure that electronic equipment is fed clean power when using a generator.
The quality of generators varies, and while most devices are happy to run from cheap generators, delicate electronic equipment wants a clean, pure sine wave, not the "modified sine wave" often found coming from generators.
There are two ways to fix this:

  • get a generator that gives "pure sine wave" output
  • clean the generator output.


Buying a higher quality generator sounds like the obvious solution, but the difference in price between a "modified sine wave" and "pure sine wave" generator of the same capacity can be significant.
Coming at the problem from a tangent, I would recommend the use of an "on-line" UPS between the generator and the sensitive load.  On-line UPSs are designed such that the input power never gets to the UPS load - all the power goes through the battery conditioning circuitry, with the input power being converted to DC, then back to AC again for the load.  This allows the UPS to be connected to "dirty" generator output, but the load to only see the "clean" power from the UPS. The use of the on-line UPS also means that there is zero fail-over time if the generator goes off line (who forgot to fill the petrol tank? Come on, own up!), and that the load can continue to work while the generator is moved, mains cable re-routed etc., giving a two-for-one benefit.
You have to be careful to choose an on-line UPS, not a line-interactive model.  Line-interactive means that the UPS will "top-up" the power to the load if the incoming power drops off a bit, but it does not mean that the power is cleaned before supplying to the load.  Line-interactive is good if you don't have to worry about the quality of the incoming power feed, but not in the scenario we are looking at here.

Ross Wakelin
Hits: 461

We have rebuilt our site using new versions of the back-end software.  We apologise if the layout is slightly different, but we think it will be easier to find your way around now.

Ross Wakelin
Hits: 462

Hmmm, maybe there is something to this security stuff after all......

--SWAT Team Raids Wrong Home Due to Unprotected Wi-Fi Network (June 28, 2012)

Police in Evansville, Indiana sent a SWAT team into a home that was the suspected origin of some threats made against police on an Internet forum. After breaking a door and a window and tossing in flash grenades, police learned that they had targeted the wrong house. Because the threats were traced to an IP address associated with the house's Wi-F network, the officers believed they had identified the culprits. However, the Wi-Fi connection was unsecured and the threats had actually come from someone at a different residence who took advantage of the open network connection. http://arstechnica.com/tech-policy/2012/06/swat-team-throws-flashbangs-raids-wrong-home-due-to-open-wifi-network/

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