Translated and edited from the irrigation-water chapter of the book True Living Organics by The Rev. The research and extension sources used to check the book’s claims are listed under References at the end.
Living soil depends on soil microbes, and the water you pour on it every few days is the input most growers never test. Part 1 explains how chlorine and chloramine in tap water affect soil life and how to remove each one. It also explains why hard water damages the root zone slowly, over months, and why softened water is the one water source that genuinely kills plants.
The Rev is the pen name of the American organic grower who wrote True Living Organics. His method, called TLO, builds a soil rich enough that you mostly just water it. True Living Organics: The “Water-Only” Philosophy explains how the method works.
This guide says so whenever it relies on The Rev’s own advice or observations. Where a claim could be checked, the guide links the research or the university extension service that confirms or corrects it. Extension services are the public farm-advice programmes run by US universities. The rest of the advice comes from the forum’s editors.
American growing books like this one give water limits in PPM. Do not copy those numbers into a Thai or other tropical grow room without first measuring your own water. Part 2 explains why. It also covers reverse osmosis (RO) water and its reject stream, fluoride, how to test your water, Cal-Mag, a ranking of water sources for this region and two watering techniques.
1. Why water matters more in living soil than with bottled nutrients
With bottled mineral nutrients, the growing medium is inert, meaning it does nothing chemically. Your water is just a starting point, and you correct it with nutrients and pH adjustment.
Living soil is not inert. Amendments are the dry organic inputs you mix into the soil, such as meals and rock minerals. The microbes that turn them into food the plant can take up live in the thin film of water around each soil particle.
Anything dissolved in your irrigation water enters that microbial habitat at every watering, for the whole cycle. In a pot, the only way out is the water that drains from the bottom. That leads to two kinds of damage, on different timescales:
- Fast (acute) damage: a disinfectant or a toxic ion harms soil organisms directly.
- Slow (chronic) damage: dissolved minerals build up in the root zone over weeks. They shift the pH, block air movement through the soil and gradually make the rhizosphere unliveable. The rhizosphere is the thin layer of soil around the roots where roots and microbes interact.
Slow damage is far more common. It is also much harder to diagnose, because nothing visibly goes wrong on any single day.
What to do: Before your next cycle, write down where your irrigation water comes from: tap, well, rain, RO or dehumidifier condensate. Then measure it with a TDS meter. This is a cheap pen-shaped meter that shows how much mineral is dissolved in the water, as a PPM figure. That reading is the starting point for every decision in this guide.
2. Chlorine and chloramine in tap water, and how to remove each one
Water utilities disinfect tap water so it stays safe on its way through the pipes. They use one of two chemicals, and each one needs different treatment.
Free chlorine escapes from standing water within a few hours to a day. Bubbling air through the water or boiling it also drives chlorine off.
Chloramine is chlorine bonded to ammonia. Utilities use it because it keeps disinfecting for longer as water moves through the pipes (US Environmental Protection Agency). Leaving the water to stand or bubbling air through it does almost nothing to chloramine. Boiling is slow and unreliable.
The Rev insists that chloramine cannot be aired or boiled out, and on this practical point he is right. If your supply uses chloramine, the old advice to leave a bucket of tap water out overnight does nothing. Singapore, for example, disinfects its tap water with chloramine.
Translator’s note: In Thailand, tap water comes from one of two state utilities. The Metropolitan Waterworks Authority (MWA, การประปานครหลวง) serves Bangkok, Nonthaburi and Samut Prakan. The Provincial Waterworks Authority (PWA, การประปาส่วนภูมิภาค) serves most other areas, and some places have local municipal or village systems. MWA says on its website that it disinfects with chlorine. No public statement was found on whether every PWA branch and local system does the same, so ask your supplier whether it uses chlorine or chloramine. Write the answer down, because it decides which equipment you need.
Removing chloramine and chlorine
- Carbon filtration, done properly. Activated carbon is the black granular material inside most water filters. It removes chloramine only slowly, so the water needs a long contact time. If you can get it, use catalytic carbon, which is activated carbon treated to break down chloramine faster. Run the water slowly through the filter.
- Carbon in an RO unit. In a reverse osmosis (RO) unit, which pushes water through a very fine membrane, the carbon stage is what removes chloramine. Do not skip or neglect the carbon cartridges.
- Chemical neutralisation, the cheapest fix. Ascorbic acid (vitamin C) or sodium ascorbate neutralises chlorine, according to a USDA Forest Service technical tip. The tip gives 1 gram of ascorbic acid per 100 US gallons (about 380 litres) of water for each 1 mg/L of chlorine. It is also widely used against chloramine. The other common choice is Campden tablets (sodium or potassium metabisulfite), which are sold for home brewing.
- Mixing vitamin C solution. Mix it fresh each time. Once dissolved, it breaks down within a day or two.
Translator’s note: In a room at 30–35 °C, mix the vitamin C solution on the day you use it, and keep it covered and out of the sun. If you use vitamin C, choose plain powder rather than flavoured fizzy tablets, which put sugar and other ingredients into the pot. Check with local suppliers which of these products you can actually buy before you plan around one. To find out whether a filter cartridge is catalytic carbon, ask the brand’s official distributor in Thailand. You can also ask what other members use in the Equipment and Supplies section.
How much harm does residual chlorine actually do?
On this point the book overstates the risk. PPM (ppm) means parts per million, and for water 1 ppm is about 1 milligram per litre. Tap water normally carries about 1 ppm of chlorine or less. One US utility reports 0.05–0.90 ppm.
Colorado State University Extension summarises research with these results:
- Water at 5 ppm chlorine affected soil organisms only in roughly the top centimetre (half an inch).
- About 65 ppm was needed to affect organisms 15 cm (6 inches) deep.
- Populations recovered to pre-treatment levels within two days after the chlorinated watering stopped.
A 2023 study by Yu and colleagues in Soil Ecology Letters irrigated soil with low-concentration chlorinated water. The researchers used metagenomics, which reads the DNA of every microbe in a sample. After 14 days there was no significant lasting change in the diversity or make-up of the microbes. Some microbial functions shifted briefly.
So chlorinated tap water is not ideal for living soil, but it is not the instant disaster the book suggests.
Where caution really is needed
The real risk comes when you mix a soluble mycorrhizal inoculant or any other microbial product straight into chlorinated water. A mycorrhizal inoculant is a powder of beneficial root fungi. In a bucket, the organisms float in the disinfectant with no soil around them for protection. Use filtered, neutralised or RO water for this step.
Order of priorities
- Find out whether your supplier uses chlorine or chloramine. This decides what equipment you need.
- If it is chloramine: use catalytic carbon with a slow flow, or neutralise with ascorbic acid or Campden tablets. Leaving water to stand is useless.
- If it is free chlorine only: carbon filtration or neutralisation is still better. Leaving water to stand removes part of the chlorine, so it is better than nothing.
- For inoculant mixes and other microbial products: always use filtered or neutralised water.
What to do: This week, ask your water supplier which disinfectant it uses. Until you have the answer, mix every inoculant or microbial product in filtered, neutralised or RO water only.
3. Hard water: damage that builds up over months
Hard water carries a lot of dissolved calcium and magnesium, plus whatever else its source adds. In a pot it acts like water in a kettle, which leaves white scale behind.
Over one to two months, salts build up around the roots. They shift the pH of the root zone, block air movement and make the zone hostile to the microbes the plant depends on.
The Rev reports that hard water hits mycorrhizal fungi especially hard. Once the fungi are weakened, he sees phosphorus lock up. The phosphorus is still in the soil, but the plant cannot take it up.
He also warns about too much iron, manganese or sulphur in well water and spring water. Spring water here means groundwater taken from a natural spring, not bottled drinking water. In his experience, manganese can spike at certain times of year, depending on rainfall. High manganese combined with falling soil pH can then kill plants fast. This is his own observation, not established research.
Seasonal swings matter more in a monsoon climate. A well tested in March may give a very different reading in September.
Translator’s note: In Thailand, March falls in the hot dry season and September in the rainy season. If you use a well, test it at least once in each season. A single reading tells you about one moment, not the whole year.
A living-soil pot normally never needs flushing. Flushing means running large volumes of plain water through the pot to wash out built-up salts. If you find yourself flushing regularly, your water is probably the cause. For diagnosis and recovery, see Troubleshooting Living Soil: Salt Accumulation, Organic Acid Damage and pH Lockout.
What to do: Measure your source water now and again in the other season. If the reading is high, or you keep having to flush, fix the water before changing your soil recipe.
4. Softened water: never use it
The book’s warning is absolute: never water with softened water, because it will kill plants. University extension advice backs this up.
A household water softener works by ion exchange. A resin inside it swaps the calcium and magnesium in the water for sodium. Iowa State University extension (Ask Extension) makes three points:
- Softened water contains high levels of sodium.
- Sodium becomes toxic to plants once it builds up in the soil.
- The problem shows up mainly in potted plants watered only with softened water over a long period.
That describes a container grow exactly. The sodium also stays in the soil, so the soil is damaged for reuse as well.
A softener does have one proper use: before an RO membrane. The Rev recommends one ahead of the RO unit when water is hard, so the membrane lasts longer. His example of hard water is about 170 PPM. The softened water is only a stage inside the system, not irrigation water. Never connect a garden tap to the softened line.
Translator’s note: Some Thai houses, condominiums and shophouses have a whole-house filter system. Check whether it includes a softener, which is usually a resin tank that you top up with salt. If it does, do not take irrigation water from any tap downstream of that tank.
What to do: Trace the pipe from your irrigation tap back to the mains. If it passes through a softener, take irrigation water from a point before the softener, or switch to another source from the list in Part 2.
Share what you find: If you have asked MWA, PWA or your local water system which disinfectant it uses, post the answer and your district below this topic. Other growers in your area will then not have to ask again. Questions about your own water are welcome here too.
Legal note: This article gives technical horticultural information for readers acting legally where they live. Cannabis is regulated differently in every country and is still illegal in several countries in this region. In Thailand, cannabis flower is a controlled herb under the Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568, in force since 26 June 2025. Activities involving it are subject to Ministry of Public Health licensing. Flower may be sold only against a PT 33 (ภ.ท.33) prescription, for a maximum of 30 days. Advertising and online sale of flower are prohibited, and recreational use is not permitted. The Cannabis Control Act is still a draft. The Cabinet approved it on 22 September 2026 and sent it to the House. Check your local law before growing. Nothing here is legal advice.
References
- The Rev, True Living Organics, irrigation-water chapter.
- US Environmental Protection Agency: Chloramines in Drinking Water
- USDA Forest Service technical tip on vitamin C dechlorination: link
- Colorado State University Extension: Impact of watering lawns and gardens with chlorinated water
- Yu et al., Soil Ecology Letters, 2023: doi:10.1007/s42832-022-0130-x
- Iowa State University, Ask Extension: softened water and plants
Further reading on Asiannabis
- Troubleshooting Living Soil: Salt Accumulation, Organic Acid Damage and pH Lockout
- True Living Organics: The “Water-Only” Philosophy, and What It Is Actually Claiming
Continued in Part 2: Irrigation Water for Living Soil: Reverse Osmosis, Fluoride, Testing Your Source and Choosing Water in Thailand (Part 2 of 2)