Ong® Jar

An attractive, artisan alternative to plastic and metal rainwater collection vessels. Collect hundreds of gallons of rainwater while adding dramatic style to landscapes, patios or entryways.

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Use & Care



Why harvest water with Ong ® jars?

Water harvested from rainfall or AC condensation conserves and replaces precious groundwater resources and eases demand on municipal storm water systems. A handheld hose attached to an Ong ® jar is allowed anytime for targeted watering in drought-prone areas, whereas broadcast sprinkling is often restricted.

Ong ® jars and similar vessels have been used for centuries in South Asia to collect rainwater in times of drought. Duang Hanesworth, co-owner of Big Grass, grew up with Ong ® jars in Thailand, where they are a staple of daily life in many rural communities. As is common in rural Thailand, Duang’s parents still use Ong ® jars for household water collection and drinking water.

Since 2005, Duang and her husband John have worked directly with Ong jar producers in Thailand and imported the vessels to the United States for sale at Big Grass. Big Grass is the only U.S. source for the Ong ® jar. Duang, John and their team continually advise customers about their rainwater catchment systems, help them design the integration of the Ong ® into landscape design, and have installed the Ong ® for customers throughout Texas.

Big Grass  is a member of the American Rainwater Catchment System Association (ARCSA) and a source for rainwater harvesting and water conservation solutions.

How do I best use the Ong ® jar for landscape and garden watering?

base-hoseOng ® jars come complete with a hose faucet fitting near the bottom of the vessel. They are perfect for use with a hand-held hose or an inexpensive soaker hose for landscape watering. If more pressure is desired for sprinkler watering or for moving water uphill, inexpensive 110v inline garden hose pumps are available at home improvement stores.

Many customers purchase multiple Ong ® jars to harvest water in different areas of their property for zone watering use. The jars may also be plumbed together to create a more extensive drip irrigation system.

With additional PVC pipe or garden hose, the drain fitting at the bottom of the jar can be used to combine multiple jars at additional downspouts or valleys into a larger rainwater harvesting system. For more information on combining larger jars, click here.

Note: For safety reasons, make sure the galvanized lid provided with the Ong ® is always securely in place.

Where do I place the jar to harvest rainwater?

Ong ® jars by Big Grass are ideal for residential and commercial landscape watering. They can be placed under or connected to downspouts, used with rain chains or simply placed under roof valleys. Typical gutter systems can be easily adapted to direct the downspout or water flow into the jar.

The metal galvanized lid that comes with the Ong ® allows for easy downspout insertion and can be easily adapted for more customized installations. Decorative reclaimed teakwood tops are also available.

To protect the vessel from excess ground moisture, place it on a solid, level, well-drained surface, including decks and concrete. For ground level placement, it is unnecessary to pour a concrete slab. However, the Ong ® should be placed on a level base made up of four standard 12″ x 12″ concrete pavers, spaced one inch apart, to allow for air space under the jar.

Ong ® jars offer a perfect option for problem landscaping areas that are difficult to access with traditional sprinkler systems due  to concrete walks, driveways or distance. Big Grass can offer guidance on these installation solutions.

Can I integrate Ong ® jars into a larger catchment system?

base-spoutWith additional PVC pipe, the drain fitting at the bottom of the Ong ® jar can be used to divert water to a distant faucet.

Ong ® jars can also be integrated with distantly placed large-volume plastic or metal vessels (1,000 gallons plus) as part of larger rainwater catchment systems. Ong ® jars can serve as attractive “first-flush” (initial roof wash) containers, while also providing a volume of water, or “point source,” for immediate gardening use. Too often, this quantity of water is wasted in conventional installations.

A qualified rainwater harvesting technician can easily retrofit the Ong ® jar in order to integrate the vessel into an existing harvesting system.

Note: For household use, use necessary filtration and purification add-ons. Without this additional purification, the water collected in the jar should not be used for drinking purposes.  Also, for safety reasons, make sure the galvanized lid provided with the Ong ® is always securely in place.

How do I move the Ong ® jar?

base-moveIf you need to re-position the jar, drain it thoroughly (use the water!) and remove the hose faucet. Although the vessel can be carefully rolled on its side, it is best to pivot it and roll it on the bottom edge in order to move it safely. Pad the vessel with blankets and remove any rocks or debris when moving it over rough ground. One person is required to move a mini-Ong ®, two people are needed to move a small Ong ® and three people to move a large Ong ®.

Ong ® jars are very durable but to avoid damage, do not move them carelessly or hit them with lawn equipment or vehicles.

In Thailand, these jars last 30 years or more with little to no maintenance.

How do I keep debris and mosquitoes out of the jar?

Big Grass offers galvanized drop-in filter baskets that can be used with the Ong jars to prevent mosquito breeding and the accumulation of leaf debris.

Alternatively, nylon mosquito netting can be cut and tied around the lip of the jar to filter debris and to prevent mosquitoes from entering the vessel. Firmly securing the metal lid that comes with the jar or the available teakwood lid also discourages mosquito breeding.

Note: For safety reasons, make sure the galvanized lid provided with the Ong® is always securely in place.


How do I clean my Ong ® jar?

Ong ® jars come with a drain plug to clean leaf or roof debris when needed. Simply unscrew the threaded plug (use the water!) to drain the jar.  Hose out the interior, flushing any debris out of the drain hole. Our drop-in filter basket prevents the accumulation of leaf debris build-up and shingle grit, minimizing the need for cleaning.

Is algae growth an issue with collected rainwater?

base-jarsIn contrast to translucent plastic vessels, algae growth is not a problem with Ong ® jars. Because Ong ® jars are made from opaque concrete, only minimal sunlight (required for algae growth) enters the jar.

How do I preserve the look of the jar?

base-stainWe custom-stain Ong ® jars based on a choice of available color and finish options. An additional interior coating of sealant helps protect the exterior finish. After staining, two coats of exterior water-based clear coat are applied to enhance color and durability.

This exterior finish can be allowed to weather naturally or can be maintained over time with widely available water-based concrete clear-coat sealants.

How do I protect the Ong ® from freezing temperatures?

base-metal-lidIn regions where temperatures regularly drop below 32 degrees Fahrenheit, the jar should be drained (use the water!) utilizing the included threaded drain plug. With a garden hose, drain the jar to the hose faucet level. Then open the threaded drain plug at the bottom of the vessel to drain the remaining water.

Leave the plug out during the winter months until the freeze warnings have passed. Rainwater or snow melt coming off the roof will simply pass through the open plug and won’t accumulate in the vessel.

In regions where sub-freezing temperatures are common during the winter, the drain plug should be removed for the season. Many plants remain dormant during the winter season, minimizing their watering needs.

Note: For safety reasons, make sure the galvanized lid provided with the Ong ® is always securely in place.