If you put tap water into a sealed water bottle (or barrel), how long will it keep for? It can't evaporate there, either.

I don't really know the answer. Many people seem to think you need to add additional purifiers and then cycle water every 6 months anyway. I'm not sure that's right, but if it is, then the water in the proposed tanks wouldn't have additional purifiers, and could basically sit their indefinitely. Maybe if the water comes in at the top and leaves at the bottom, it would guarantee enough circulation that the fresh chlorides in the incoming water would diffuse through the entire system. It's just something to be thought about, rather than an insurmountable obstacle.

Bugs get everywhere. Often treatments don't so much kill them completely as reduce their numbers to what the human immune system can deal with. So a few remain and given time, they can grow back.

If you think the bugs are coming in from upstream.

I'm not sure filtering worth having can be fast enough for the through-put needed (and I've avoided domestic filters as just another place for bugs to grow). Ultra-violet light treatment could be more practical.

In usual UK systems, 2 can't happen. The mains pipe empties above/into a cold water tank in the attic, and most of the house is fed from that. If the mains pipe goes in reverse, it will suck air, not water.

1 is a good reason, though.

Seems like it would add such a tiny incremental cost to initially setting up a home's plumbing system to routinely add some sort of check valve that simply blocks the water supply from flowing backwards. Perhaps something that requires manual intervention to reset. Otherwise, once the reverse flow subsides, a valve that automatically re-opened could then allow scenario #1 to occur.

> long enough for the chlorides to evaporate

Any idea how long that would take?

I cannot address home systems, but have a bit of experience with automatic water systems for animals. Many systems hyperchlorinate water between 10-15ppm at a central chlorinator before entering a manifold, which distributes the water to various rooms. Another manifold branches off supplying water to each animal rack and is again branched to supply water to each cage. Animals access the water through a “licks it” which allows the water to come through the valve as the animal licks a small internal valve.

If you test the water entering the rack, it will run between 8-10ppm (so it has lost between 2-5ppm) and if you test the water at the cage valve it runs around 0-2ppm. Water pressure at the cage level is very low, so regardless of whether or not you have a check valve, bacteria, viruses and fungi will enter the system (from the animal’s mouth) as the animal licks the valve. Generally the systems are automatically flushed several times per day to ensure enough chlorine is flowing through the system.

So what does this have to do with a home system? For most municipal water systems, chlorine levels will be around 0.5ppm at the tap level. If you have a system that does not flush adequate amounts of chlorinated water through on a daily basis, the chlorine levels will drop, most likely to 0.0ppm. Why? The various organic compounds that are in almost everyone’s water supply will bind forming chlorinated-hydrocarbons so there will be no free chlorine for bacterial-cidal / bacterial-static functions.


I don’t if any of this helps or is just a bunch of useless information, but for what it is worth (2 cents)-

Pete

I have been looking enviously at the Quooker Boiling Water Tap, it is very expensive at around $1200 but will boil water to 110C and delivery water at the tap at 100C. This would remove any bacterial or Viral hazard.

http://www.quooker.com/07_uk/site.html

Looking at the power requirement for the Quooker Tap it could potentially be used with an off grid solar PV setup powered from a 80-120W solar panel/80amp SLA battery/800W inverter system to provide around 4-5 litres of sterilized boiling water per day.

Aquarium owners are supposed to let tap water stand for 24 hours before putting it with fish. That's probably conservative.

As Brangdon points out, probably 24 hours at most. Besides aquarium lovers, the typical microbiology lab handbook will tell you to toss out any diluted bleach solutions you mix up for disinfecting purposes fairly quickly. The times vary, but never more than 24 hours. So, say, 24 hours to have any sort of hope of killing any nasty bugs. You may still be able to detect it in the water after that point, but it would be useless.

I'm kind of bummed that I can't seem to find that bleach thread from a while back where I went into this topic in depth. I wonder where it went...

Pete makes a good point that any bleach in the water will be continually reacting with any organic matter. Although the lab example is a bit different since the animals are actively introducing organic materials by using that water lick device. However, as with benjammin's setup, if you had some sort of biofilm in the tanks, bleach could react with that.

Anyway, so that is one of the reasons many municipalities have switched from using chlorine to using chloroamines in their water supplies--the persistance over time.

Are we all assuming that water MUST be chlorinated to be safe? Could that be a false assumption?

My local municipal water supply doesn't routinely add chlorine (or fluoride, fortunately) to the water supply, just a jolt in summer to clean the tanks the water is pumped from.

Sue

If the water is coming from a well, the need to treat with any chemical agent is reduced. However, many municipal water sources come from lakes, streams/rivers and reservoirs, all of which would require water treatment, unless they have moved to other (UV, Reverse Osmosis (RO), ultrafiltration, etc.) methods of bio-inactivation.

Pete