The short answer: put the block in a container that holds at least 100 litres, add 20–30 litres of clean water, wait until it has soaked through (30 minutes to a few hours, longer in cold water), then break it apart by hand or with a fork and add water to any dry core. A 5 kg block gives roughly 60–75 litres of loose coco peat; published figures run from about 50 to 100 litres because expansion depends on the material, how fast it is wetted, and how the volume is measured. Before you plant in it, check EC, pH, sand and moisture on a sample.
Key facts
- The standard export block is 5 kg, about 30 x 30 x 12 cm, compressed roughly 5:1 (Bhutan Ministry of Economic Affairs project profile; Hort Americas product data; Profile Products technical data sheets).
- Published yields per kilogram range from 9–10 L (The Coco Depot) through 13 L (Profile Products Grade A Washed) and 14 L (the benchmark quoted in HortiDaily) up to 17–20 L (Evergreen Exports, in HortiDaily, 2023).
- Coir pith holds 750–1100% of its dry weight in water and has a bulk density of 0.04–0.08 g/cm³ (Evans, Konduru and Stamps, HortScience, 1996).
- Slower hydration gives more volume; halving the mean particle size raises bulk density by about 26% (Carve Bio guide citing Manickam and Suresh, 2011).
What a 5 kg coco peat block is
Coco peat (coir pith, coir dust, cocopeat) is the spongy material left over when the long fibre is extracted from coconut husk. About two thirds of the husk by weight ends up as pith (Coir Board of India figures reproduced in the Bhutan project profile). Loose pith is light and bulky, so for shipping it is dried, sieved and pressed into blocks.
The common trade specification for a block, as listed by Indian exporters and summarised in the Bhutan Ministry of Economic Affairs project profile, is:
| Parameter | Typical block specification |
|---|---|
| Weight | 5 kg (Indian Standard IS 19103:2025 allows plus or minus 100 g) |
| Size | 30 x 30 x 12 cm; some makers press 30 x 30 x 10 or 30 x 30 x 15 cm |
| Compression ratio | About 5:1 by volume; Profile Products lists 5:1, 6:1 and 6.3:1 for its three block products |
| Moisture at pressing | Below about 18–20% by weight |
| Sieve size | 5–6 mm screens are common; 10 mm for coarser grades |
| Sand and fibre | Below 3% in a good washed grade (Profile Products) |
The Bureau of Indian Standards published IS 19103:2025, Coir Pith Block — Specification, and IS 17739:2024 for raw coir pith, which caps sand content at 2%. Ask your supplier whether they test to either standard.
Blocks are sold washed or unwashed, and sometimes buffered. The difference matters more than the block format, and it is covered in buffered vs unbuffered coco peat. Everything below applies to any block.
How to hydrate a coco peat block, step by step
You need the block, clean water, a container at least twice the expected final volume, and a garden fork or your hands. A 90–120 litre tub, a wheelbarrow or a clean bunker works for a single 5 kg block.
- Check the water. Use the cleanest water you have. Coir takes up whatever is in the water, so high-salt or high-alkalinity water raises the EC and pH of the finished medium. For sensitive crops many growers hydrate with their normal feed solution rather than plain water.
- Place the block flat in the container. Lay it on the largest face so water can reach it from below and above. If you have time, score or split the block first; broken pieces wet faster than a whole block.
- Add 20–30 litres of water. Published guidance for 5 kg blocks is close: 20–25 L (Biology Insights), 25–30 L (Indian supplier listings), 6–8 US gallons, 23–30 L (Fedco Seeds). Start at the low end; you can always add more.
- Wait. In warm water most of a block loosens within 30–60 minutes (Coir.com; Biology Insights). Cold water, a very dense block or a low ambient temperature can take several hours. Fedco Seeds tells its customers to allow about twenty hours, "or until it's wet through and breaks apart". If you are in no hurry, slow is better: the Carve Bio guide notes that slower hydration gives more final volume.
- Break it up. Turn the mass over with a fork and crumble it by hand, paying attention to the middle layers where dry pockets hide. Add a litre or two of water at a time to any dry, pale core until the whole lot is uniformly dark.
- Check the moisture. Squeeze a handful hard. A few drops should come out. A steady stream means too wet; nothing at all means too dry.
- Drain if needed. If free water pools at the bottom, leave the coco peat in a container with holes for an hour, or spread it on a clean surface. Excess water also carries away some of the remaining salts, which is useful if the EC is higher than you want.
- Test before use. Take a sample and measure EC and pH (see below). Then fill pots, trays or beds, or blend with husk chips, perlite or compost.
Warm water speeds up the process (Carve Bio notes that blocks in the Netherlands are sometimes hydrated with hot water), but it is not required. For a greenhouse that uses many blocks a day, the same steps are done in a bunker or a coir expansion machine; Profile Products notes on its data sheets that its blocks "can be expanded with water in a bunker or processed through most coir expansion machines".
How many litres does a 5 kg block make?
This is the question buyers argue about most, so here are the published figures side by side, converted to litres per kilogram so they can be compared.
| Source | Figure | Per kg |
|---|---|---|
| The Coco Depot, quality-check guide | 1 kg expands to 9–10 L | 9–10 L |
| Profile Products, Coir Buffered TDS (2024) | 10–13 L/kg, 5:1 | 10–13 L |
| Profile Products, Coir Grade A Washed TDS (2025) | 13 L/kg, 6:1 | 13 L |
| Carve Bio guide (coarse / medium / fine grade) | 13 / 14 / 15 L/kg | 13–15 L |
| HortiDaily (2023), buyer benchmark | 1 kg "expected to expand to about 14 Litres" | 14 L |
| Fedco Seeds, 5 kg block | about 2.5 cubic feet (71 L) | about 14 L |
| Coir.com, 5 kg block | 16–20 US gallons (61–76 L) | 12–15 L |
| Bhutan project profile, Indian exporter spec | 17 L/kg; elsewhere 55–60 L rehydrated yield per block | 11–17 L |
| Profile Products, HydraFiber + Coir TDS (2025) | 16–17 L/kg, 6.3:1 | 16–17 L |
| Evergreen Exports (HortiDaily, 2023) | 17 L/kg from the lowest pith bed, 20 L/kg from the top bed | 17–20 L |
| Typical marketplace listings | 70–80 L per 5 kg block | 14–16 L |
So a realistic expectation for a 5 kg block is 60–75 litres, with honest specifications ranging from about 50 to 100 litres. If a supplier quotes 80 L or more, ask how it was measured.
Why the figures vary
- Raw material. Pith from the top of a storage bed expands more than pith from the compacted bottom, and older coconuts give more expansion and water retention (Mohamed Raashid of Evergreen Exports, in HortiDaily, 2023). On the other hand, a Sri Lankan study found no significant difference in expansion ratio between fresh pith and pith aged for two or four months (Dunsford, Dissanayake and Weerasinghe), so age alone is not a guarantee.
- Particle size and fibre content. Fine, dusty pith packs denser: halving the mean particle size raises bulk density by about 26% (Manickam and Suresh, 2011, cited by Carve Bio). More short fibre and chip in the mix raises the expanded volume and air porosity but lowers water holding (Aileen Reid, Understanding Coir, 2021). The Carve Bio guide gives 13 L/kg for chips, 14 for medium and 15 for fine grade.
- Moisture at pressing. Every extra percentage point of moisture raises bulk density by about 1.07% (Manickam and Suresh, 2011). A block pressed wet weighs 5 kg with less actual coir in it.
- Factory drying. Over-drying damages the structure. Fernando and Amarasinghe found that oven drying coir pith "resulted in rupturing of the cells and case hardening" and that 140 °C was the optimum drying temperature for later re-expansion (SpringerPlus, 2016; Journal of the National Science Foundation of Sri Lanka, 2017). A block that stays hard and gritty after soaking has often been over-dried, not over-pressed. Pressing itself does little harm at normal pressures: an Indonesian study pressed 8 L of cocopeat at 10–50 bar and recovered 9.55–9.85 L after adding 5 L of water (Widyatmoko et al., 2026).
- Hydration speed and water temperature. Slow, gentle wetting gives more volume than fast flooding (Carve Bio).
- How the volume is measured. This is the biggest source of disagreement. Some labs pour the wet coir loosely into a measure and read the volume; others tap or settle it. Some drain to container capacity first, some do not. Some use a 1 kg sample with a fixed water volume ("yield, 1 kg method" on the Profile Products data sheets), others expand a whole block. The Coco Depot's bench method is to mix 1 kg of crushed block with 3 parts water, let it expand fully and measure "without compressing", which gives its 9–10 L figure. A specification is only comparable when it states the method, the water ratio, and whether the volume is loose or settled.
Practical advice: ask for the yield per kilogram, the method, and the moisture content at the time of weighing. Then hydrate one block yourself with your own water and measure it loosely filled into a container of known volume. That number is the one to plan with.
Checking a block on arrival
A cheap EC meter and pH meter, a bucket and a kitchen scale cover most of this. Test a sample from the middle of a block, not the surface, and test more than one block per shipment.
| Check | How | What to look for |
|---|---|---|
| EC | 1:1.5 volume extract (Dutch method) or 1:5 extract (EN 13038); the method changes the number | Washed coir below about 0.7 mS/cm (1:1.5); buffered below 0.5 (Profile Products). Never compare figures from different methods |
| pH | 1:5 or 1:1.5 extract in neutral water, or the pour-through method after wetting | Coir is naturally slightly acidic to neutral, 5.6–6.9 across sources (Evans et al., 1996); most data sheets give 5.5–6.5 |
| Sand | Stir about 1 kg into clean water for 15 minutes; coir floats, sand settles; dry the residue at 105–120 °C and weigh (The Coco Depot) | Below 2–3% (IS 17739; Profile Products). Sand adds weight you pay for and abrades equipment |
| Moisture | Weigh 100 g, dry at about 100–105 °C to constant weight, reweigh | Below 18–20% is the usual pressing specification. Wet blocks mean less coir per kilogram and a risk of mould |
| Fibre and particle size | Pass a hydrated sample over a 6 mm sieve; look at the long fibre fraction | Fine screened pith for propagation; more fibre and chip for long-term crops. Agree the grade before you order |
| Appearance and smell | Look and smell after soaking | Uniform dark brown, earthy smell. Grey or white mould, a sour smell, or hard lumps that do not break are warning signs |
EC methods and what the numbers mean are explained in detail in the buffered vs unbuffered article linked above.
Storing coco peat blocks
Compressed blocks are stable if kept dry. The moisture limit that lets a block ship and store well is about 18–20% by weight (Bhutan project profile; Profile Products data sheets). Keep blocks:
- on pallets, off concrete floors, under cover and out of rain and direct sun;
- in their original wrapping until needed; a wet block swells, cracks and may mould;
- away from fertiliser or chemical spills, since coir absorbs liquids readily;
- first in, first out. Suppliers commonly quote a shelf life of around two years in dry storage. Blocks do not spoil in the way compost does, but a block that has been damp and dried out several times may wet unevenly.
Hydrated coco peat that you cannot use within a few days should be kept covered and moist, not sealed wet in a warm place, or dried out again before storage.
Blocks, briquettes and grow bags
The same coco peat is pressed into three formats. The choice is about labour and handling, not chemistry.
| 5 kg block | 650 g briquette | Grow bag or slab | |
|---|---|---|---|
| Typical size | 30 x 30 x 12 cm | about 20 x 10 x 6 cm | pressed slab inside a plastic sleeve, e.g. 100 x 15–20 cm |
| Expanded volume | roughly 60–75 L | roughly 7–10 L (Coir.com, Seeds Ireland, Dr Greenthumbs listings) | the slab expands inside the bag to fill it |
| Water to hydrate | 20–30 L | 3–5 L | via drippers in place |
| Who it suits | nurseries, potting-mix producers, soil improvement, bulk hydroponics | retail, hobby growers, small trials, exact portions | greenhouse fruiting crops planted directly on the slab |
| Main cost | hydration labour and equipment | higher price per litre | fixed format, no blending |
Blocks are the cheapest way to ship coco peat per litre and the most flexible to use, because you decide the blend and the container. Briquettes are the same material in a size one person can hydrate in a bucket. Grow bags save the hydration step entirely for crops like tomatoes and cucumbers. The trade-offs for commercial growers are compared in grow bags vs blocks.
What coco peat blocks are used for
- Potting and nursery mixes. Hydrated block coir replaces part or all of the peat in a mix. The University of Kentucky Center for Crop Diversification lists coco coir's strengths as moisture retention, aeration, light weight and renewability, and its weaknesses as salinity and sodium levels and shrinkage as it decomposes. Washing and the right blend address both. See nurseries.
- Hydroponic and soilless beds. Expanded coir in troughs, pots or open beds for leafy greens, herbs and strawberries. Coir keeps air in the root zone even when wet and re-wets easily after drying, unlike sphagnum peat (Bhutan project profile). See hydroponics.
- Seed starting and propagation. Fine screened, low-EC coir with the long fibre removed is the usual grade for plugs and trays.
- Soil improvement and mulch. Coir pith added to field soil holds 400–600% of its weight in water and releases it slowly (Bhutan project profile).
- Other uses. Animal bedding, reptile substrate, composting toilets and worm bins use hydrated coir because it absorbs liquid and smells neutral.
Whatever the use, remember that coco peat holds nutrients well but contains little nitrogen, calcium or magnesium. Feed from the start, and let the coir drain to the squeeze-test point before planting so roots get air from day one.
For the block specification itself, see coco peat blocks. If you are specifying blocks for a greenhouse, nursery or potting-mix line and want a sample to run through these checks, contact us.
FAQ
How much water does a 5 kg coco peat block need?
Plan on 20 to 30 litres of clean water for a 5 kg block. Published supplier guidance ranges from 20–25 L to 25–30 L, and one US seller says 6–8 US gallons (23–30 L). Start with the lower amount, break the block up, and add more only to any parts that stay dry.
How many litres does a 5 kg coco peat block make?
Most 5 kg blocks give about 60 to 75 litres of loose coco peat. Published yields range from roughly 10 to 20 litres per kilogram depending on the grade, how slowly it is hydrated and how the volume is measured, so always ask for the test method behind a figure and check one block yourself.
How long does it take to hydrate a coco peat block?
In warm water most of a block loosens within 30 to 60 minutes. In cold water or with a very dense block it can take several hours, and some suppliers advise leaving it about 20 hours to wet through fully. Slower wetting tends to give slightly more volume.
Should I use hot water to expand coco peat?
Warm water speeds up expansion and some growers in Europe use hot water, but it is not necessary. Room-temperature water works if you give it time. Avoid boiling water; it adds a scald risk and there is no evidence it improves the finished medium.
Why did my block expand less than the label said?
Common reasons are a very fine or wet-pressed grade, over-drying at the factory that case-hardens the pith, fast flooding rather than slow soaking, or simply a different measuring method. Loose, freshly hydrated coir reads much higher than coir that has been tapped or left to settle.
Do I need to wash or buffer coco peat from a block?
Test the EC first. If the block is sold as washed and your reading is low for the method used, you can use it as is. If the EC is high, flush with clean water and drain. Buffering with calcium is a separate step chosen for salt-sensitive crops; many crops do well on well-washed, unbuffered coir.
Can I store a coco peat block after opening it?
Yes. A dry, unhydrated block keeps for a long time if it stays dry, under cover and off the floor; suppliers commonly quote about two years. Hydrated coir should be used within a few days or dried out again, because warm, wet coir can grow mould.
Is coco peat from a block the same as a grow bag?
Usually yes, the same washed and sieved pith is pressed either into a free-standing block or into a slab inside a plastic sleeve. The difference is handling: a block is hydrated and used in any container or blend, while a grow bag is hydrated in place and planted directly.
Sources
- Bureau of Indian Standards: IS 19103:2025, Coir Pith Block — Specification; IS 17739:2024, Raw Coir Pith — Specification (2024–2025)
- Ministry of Economic Affairs, Royal Government of Bhutan: Project Profile on Coir Pith Block (compiled Indian coir pith specifications and Coir Board of India data) (2020)
- Profile Products LLC: Technical Data Sheets for Profile Coir Grade A Washed (2025), Profile Coir Buffered (2024) and HydraFiber + Coir 5 kg Block (2025)
- HortiDaily: "People tend to choose their coir pith based on EC, sand content and expansion volume", interview with Mohamed Raashid, Evergreen Exports (2023)
- Evans, M.R., Konduru, S. and Stamps, R.H.: Source variation in physical and chemical properties of coconut coir dust, HortScience 31(6) (1996)
- Fernando, J.A.K.M. and Amarasinghe, A.D.U.S.: Drying kinetics and mathematical modeling of hot air drying of coconut coir pith, SpringerPlus (2016)
- Fernando, J.A.K.M. and Amarasinghe, A.D.U.S.: Effects of retting and drying on quality of coir pith and coco discs, Journal of the National Science Foundation of Sri Lanka 45(1) (2017)
- Dunsford, Dissanayake and Weerasinghe: Evaluation of Coir Pith Aging in Enhancing Expansion Ratios for Sustainable Land Use in Agriculture, University of Sri Jayewardenepura forestry and environment symposium proceedings
- Widyatmoko, R.H. et al.: Analysis of the Effect of Pressing Pressure Variations to Physical Characteristics and Expansion Performance of Cocopeat Blocks, Buletin Poltanesa 27(1) (2026)
- Manickam, T. and Suresh, K.: International Journal of Engineering Science and Technology 3(4), as cited in the Carve Bio coir pith guide (2011)
- Carve Bio: Coir Pith Liters per kg: Loose Bags and Blocks (guide) (2025)
- Reid, A.: Understanding Coir, The Passion Vine, Passionfruit Australia (reproduced from the Strawberry Growers Association of Western Australia) (2021)
- University of Kentucky Center for Crop Diversification: Selecting Growing Media for Soilless Systems (CCD-ER-02) (2025)
- The Coco Depot: 5 most important quality checks for coco peat (knowledge article)
- Coir.com: Hydrating Coco Coir (guide)
- Fedco Seeds: Coir Blocks product information
- Hort Americas: Washed 4.5 kg Coco Coir Peat Block product information
- Biology Insights: How Much Water Do You Need for a Coco Coir Brick? (Richards, 2026)
- Gnanasekaran, B.: Washed, Low-EC, or Buffered? How to Specify Coco Substrate for Your Crop, Greenhouse Grower (2026)