Jan. 16, 2020
Public Service Announcement:
We just got a request for some simple-but-proven ways to test the general water quality of your Merida City (JAPAY) water … or any chlorinated city water …. to determine if there is very likely ~no~ bacterial contamination in your home’s city water.
Here are 3 simple steps (tests) you can do at home:
1. Take a water sample at the city water meter for your house (or from a spigot close to the meter) and test that sample for “free chlorine” using a swimming pool tester.
… If the incoming JAPAY City water tests positive, for acceptable “free chlorine” levels … ( 0.4 to 1.2 ppm Free Chlorine) … then GREAT … there’s enough disinfectant to ensure no bacterial contamination.
2. Inspect the tinaco (and ground level cistern if there is one) … Make sure there is no accumulated detritus (leaves, dead birds, etc). If present: Remove any detritus & clean & disinfect the tinaco.
If the water in your tinaco looks clean & smells clean … then:
… Use your swimming pool chlorine tester to test the “free chlorine” levels in your tinaco water. … If the tinaco water tests positive, for acceptable “free chlorine” levels then GREAT … there’s enough disinfectant to ensure no bacterial contamination.
3. Go to your kitchen sink tap & bathroom sink taps (where you brush your teeth) … Use your swimming pool chlorine tester to test the “free chlorine” levels at your two main sink taps … If the sink tap water tests positive, for acceptable “free chlorine” levels then GREAT … there’s enough disinfectant to ensure no bacterial contamination.
Past testing of Merida JAPAY city water has shown that 3% of home’s meters had no free chlorine, and had fecal coliforms in the water coming through the meter. If this is true for your home’s meter, CONTACT JAPAY & file a complaint (there’s likely an underground leak in the pipes under the streets) …
Past testing of Merida JAPAY city water has shown that 26% of home’s kitchen sink water samples had no free chlorine, and had fecal coliforms in the water coming through the kitchen sink faucet. If this is true for your kitchen or bathroom sink … when your meter water tested positive for “Free Chlorine” … then you have significant contamination somewhere in your home’s plumbing.
If you have no free chlorine in your sink-tap water:
Typically, the in-home contamination comes from dead decaying organic matter (detritus) in your tinaco or cistern. … If your tinaco (and cistern) test positive for “Free Chlorine”, but your sinks do not have any “Free Chlorine” remaining in their water, then you need to clean your home’s plumbing.
After cleaning detritus from the system (organic gunk, like leaves, dead birds etc) … Then disinfect the home water system: Put ¼ cup of unscented laundry bleach into a standard 1100 L tinaco (300 gal) … to get swimming pool levels of free chlorine for the next 2-3 days.
If you want professional testing to determine the typical kinds of contamination found in Merida home’s water, then consider ordering one of the tests listed in this .pdf file:
Click to access LQM841126MG8.pdf
If you want professional testing to determine the typical kinds of contamination found in Merida home’s water, contact one of our local water quality laboratories. Since we have had no experience with the current laboratories, we cannot vouch for the relative quality of any specific laboratory – but fecal coliform testing is a pretty simple & reliable test.
We welcome readers to volunteer (comment) on their experiences with any of our local water testing laboratories.
* * * *
Feel free to copy while giving proper attribution: YucaLandia/Surviving Yucatan.
© Steven M. Fry
Read on, MacDuff…
Surviving Yucatan 
Working in real estate in Maine I am often involved with water tests for well water. The first thing to do before taking a test at the sink or bathroom sink is to remove the strainer (if you can here!) and disinfect it and the opening of the faucet with bleach. It is simple to pour a little bleach into a small glass or cup and hold it up to immerse the end in bleach. Then flush out the bleach very well before taking the sample. It can be a significant source of contamination.
If the faucet is contaminated, why think the rest of the system is clean?
It’s easy to just put ¼ cup of bleach into your 1,100 L (300 gal) tinaco, to disinfect the whole system … shower heads (spraying water that trickles into your eyes, nose & mouth) … bathroom sinks (teeth brushing & face-hand washing) … just that ¼ cup of bleach safely & reliably disinfects it ALL.
😉
Dr. Steven M. Fry,
Ph.D Chemistry, Public Health & Environment
Dr. Steven M. Fry, my name is Juan P Flores, I am a urologist interested in water quality in Yucatán, it would be great if I could get in contact with you by mail, thanks for the information you posted before. I will be looking forward to contact you. best regards
steven.m.fry@gmail.com
I read your article about testing your water. I’m in Baja and know our water is bad. What is the best way to purify it to wash dishes, veggies etc. without using Clorox?
Sent from my iPad
>
Dilute bleach ( ¼ cup per 1100L ~ 300 gal tinaco ) is safe for cleaning the home water entire system …
For fruits & veg … nothing works except dilute bleach … ( Microdyn & Bacdyn and other BOGUS “colloidal silver” – plata products do NOT work on common Mexican microbial contamination. 😦 )
https://yucalandia.com/science-health-issues/salmonella-food-contamination-in-mexico/
**Bleach Dilution Disinfection Protocols:
~ Stored Water Treatment (tinacos etc): 10 mL (1 tsp) bleach per 100 L of non-turbid clear water or 1/4 cup of bleach per 275 gal tinaco makes water microbially safe in 15 minutes.
~ Toilets and Sinks: Apply bleach without dilution via spray or brush for 10 minutes and rinse.
Drinking water: 2 drops of bleach per liter of clear water (20 drops per mL) and wait 15 min.
~ Fruits and Vegetables: Wash & scrub thoroughly first to remove dirt, then 10 drops bleach per liter of water and soak for 5 minutes. Rinse thoroughly.
~ Floors and bathroom surfaces (tub & shower): 1/4 cup (60 mL) bleach per gal of wash water and leave it on the surface for 5 minutes before rinsing.
~ Children’s Plastic Toys: Remove dirt first with soap and water, then use 1/4 cup (60 mL) bleach per liter of water and soak for 5 minutes and rinse.
~ Baby Bottles & Nipples: 1 drop of bleach per liter, soak for 2 minutes and rinse.
~ Other Plastic Objects: Apply straight bleach for 5 minutes and rinse – note that this might cause a permanent bleaching of some plastics.
~ Glasses and Plates: 1/4 cup (60 mL) per gallon of dish washing soapy water, scrub off food residues, and allow to soak for 5 minutes.
Notes:
– Only use unscented normal bleach for these purposes: do not use scented or non-splash bleach. (Blanqueador de Ropa)
“Apply bleach without dilution via spray…”
Can you recommend where to buy a spray bottle that holds up to chlorine bleach? With all the various spray bottles I’ve tried, either the spray mechanism just quits working after a short while, or something within the spray mechanism reacts to the chlorine and out comes a dark, rusty brown spray.
We found better quality spray bottles at Super Aki.
Since we have to re-charge the spray bottles with fresh bleach every day, you want to spray out the old exhausted solution out of the sprayer every time every time before you use it… spraying out any brown liquid from the exhausted disinfecting solution sitting in the sprayer, to spray only fresh disinfectant on the counters. 😉
Dr. Steven M. Fry
In regard to: “Stored Water Treatment (tinacos etc): 10 mL (1 tsp) bleach per 100 L of non-turbid clear water or 1/4 cup of bleach per 275 gal tinaco makes water microbially safe in 15 minutes” How often would you suggest doing this?
On another note, to prevent a lot of sarro in your water system would you suggest putting vinegar in the tinaco. If so, about how much and how often?
Good questions …
I treat our tinaco either twice a year, or whenever our daughter & her family or other guests from the USA come to visit.
Re Sarro in your tinaco… You would have to add so much vinegar to a Yucatecan tinaco to inhibit sarro, that the water would taste pretty bad.
The problem with trying to add acid, is that every time you use about ½ the tinaco volume (150 gal) you would have to add more acid … adding acid all the time to inhibit sarro formation.
😦
Steve
Is it safe to use a swimming pool chlorine puck in the tinaco?
Not really.
BTW … good question.
The pucks almost always quietly contain extra ingredients – that are NOT good to drink.
Every swimming pool puck we’ve seen also contain Cyanuric Acid.
Cyanuric acid is added to all pucks to protect Free Chlorine from sunlight’s UV-light shining on the pool.
Cyanuric Acid is not good for our kidneys. The small amount of pool water that people swallow is so small during swimming, that the amount of Cyanuric Acid swallowed is not a problem.
Notice that making soup, drinking water, water for pets mean we shouldn’t have Cyanuric acid in our tinacos.
IF you NEVER drink that tinaco water … and if NO ONE (not even pets) drink or eat that tinaco water … then using a puck would be OK.
😉
Steve
How often do you recommend putting a little extra bleach in the tinaco?
I inspect and dose our Merida-JAPAY purified city-water filled tinacos & copper pipes a minimum of about 4 times a year. When guests/family come from the USA, I do additional checks and dosing about 3 days before they arrive.
Still, it all depends on quality of your water … and on the materials & conditions of your system. If you have white PVC tubes on the roof that act as algae gardens, you may need to dose every 2 weeks. … If you have well water, and white tubes on the roof, you may have to dose weekly.
The yellow-ish gold CPVC exposed to sunlight still grows agae, just more slowly. … the dark blue PVC is supposed to grow no algae at all (like copper tubing). … while copper tubing is still the best, because the copper tubing slowly degrades, leaching a little copper into the hard basic water here all the time, and the free Copper ions are decent algicides. 😉
Dr. Steven M. Fry