Hydroponic Flood & Drain Systems

How flood and drain works

Ebb and flow — flood and drain — parks pots of medium in a sealed tray. A timer-driven pump lifts solution from a reservoir underneath; the tray fills and the medium wets; the timer then cuts out and gravity sends the solution back down. What matters is the empty half: as the level falls, fresh air is drawn into the root zone. That is why you cycle the tray instead of leaving it standing full.

How often you flood is a medium question. Clay pebbles barely hold water and empty in seconds, so they want short floods often; rockwool and coco stay wet for hours and need far fewer. Pair them wrongly and roots sit drowned, or they dry out between cycles.

What this collection stocks

Flood and drain trays

The USA Style 3ft x 3ft tray is built for this job: 900 x 900 x 110mm, UV-stabilised plastic, a 4mm wall, so a tray full of wet pots does not warp. Garland's squares are the general-purpose pair — the 80cm holds 76.8L and the 100cm holds 100L — both 12cm deep, recycled polypropylene, with ridges in the base that hold pots above any standing solution. Every size we carry is listed on Flood & Drain Trays.

Gravity-fed self-watering systems

Skip the pump and the wall socket and you still get a similar result. Autopot's Hydropak 2 Pot Starter Kit ships a 35L tank, one Smart Valve, two 10-inch pots, root control mats, tubing, fittings, nutrient and a perlite/vermiculite mix. Once the tray is empty the valve opens; once it has refilled the valve closes — no run-off, no daily checking. Autopot advise no more than four Hydrotray units off a single 35L tank. The same system continues through the 8 Pot kit and the Hydrotray Single 12 and Double 10 modules.

GoGro uses a different valve for the same idea. Neither the 15L module nor its 25L sibling needs electricity — the GoGro valve meters solution from a central tank. To start a system you want the reservoir connection kit bag, which carries the fittings, an inline filter and a tap.

Bubblers and watering control

This page also lists three PLANT!T Aeros units: a bare module, the Aeros One (twin 2500 air pump), and the Aeros IV Master four-pot unit (two air pumps plus a water pump). Those are deep water culture, not ebb and flow — go to DWC systems if that is what you came for. For gravity systems, the PLANT!T Water Timer hangs off a tap or a gravity feed: run times 1 to 120 minutes, intervals from an hour to a week. It is not a mains timer for a submersible pump.

How to choose

1. Pumped or gravity, first. Timer control is the pumped answer. Weeks unattended and no power draw is the Autopot or GoGro answer. Neither is the upgrade of the other.
2. Measure the footprint, then count pots. What we stock here is 800mm, 900mm and 1m squares. Fit the tray to the space you have.
3. Set the cycle from the medium. Frequent short floods suit clay pebbles; rockwool or coco want fewer. Both live under grow mediums.
4. A tray is not a system. A pumped build still needs a submersible pump, a reservoir the tray can drain back into, a timer, and enough fall between them. The tray does not include those.
5. Depth and wall thickness matter. Wet pots are heavy. Purpose-built trays quote wall thickness because that is what stops a loaded table bowing in the middle.

Completing the build

Shop pumps on water pumps, tanks on tanks and reservoirs, and media on grow mediums — clay pebbles and rockwool are the usual pair for this method. The number that actually decides the crop is the solution, not the tray: start with the store's guide to pH in a hydroponic system, then walk a first crop through growing hydroponic tomatoes at home.