IWS FlexiTank Without Pipes & Pump — Flexible Hydroponic Reservoir for Flood & Drain Systems
Best for: Growers running IWS flood and drain systems who want a reliable, space-saving reservoir without the pump and pipework
Our thoughts
IWS FlexiTanks have been tested to destruction and never faltered. If you're already committed to flood and drain growing, this is proper kit — built to work with IWS brains, designed to pack away flat, and made to last. One growers trust for good reason.
The IWS FlexiTank Without Pipes & Pump is a standalone flexible fabric reservoir designed as the nutrient storage backbone of IWS flood and drain hydroponic systems. Unlike rigid plastic tanks, it collapses flat for storage, sets up in minutes, and gives you full control over your ebb and flow cycle without the usual space compromise.
This is the tank-only version — you supply your own pump and pipework, or integrate it into an existing IWS system. It comes with all the fittings you need to connect to IWS brains and compatible 13mm and 25mm pipework.
How flood and drain systems work
Ebb and flow hydroponics flood your growing medium with nutrient solution, then drain it back into the reservoir. This cycle forces fresh air into the root zone while nutrients circulate — your plants get oxygen, water, and food all at once. The result: faster growth, reduced nutrient waste (growers typically save 10-30% on fertiliser), and plants that thrive on simplicity.
The FlexiTank is where all that drained solution goes, ready to be pumped back up for the next flood cycle.
How it compares
FlexiTanks sit between budget DIY solutions and premium rigid plastic reservoirs.
-
vs. rigid plastic tanks: Same durability and capacity, but collapses flat and costs less. No storage nightmare
-
vs. gravity-fed systems (AutoPot): Flood and drain gives you more control and faster growth rates, though it does need a pump and timer
-
vs. generic fabric tanks: IWS FlexiTanks are purpose-built for IWS brains with reinforced fittings, proper leg support, and proven reliability in UK grow rooms
If you want a proper flood and drain setup without buying a rigid tank you can't shift, this is where you land.
Usage guidance
Setup and assembly
Unroll the tank, slide the five support legs into the vertical slots on the fabric, and fit your irrigation fittings into the reinforced holes. You're ready to connect pipework and pump within minutes. It packs down just as fast.
Tank capacity and grow room size
Available in 50L, 100L, 225L, 400L, and 750L sizes. Choose based on your number of pots and flood cycles — bigger tanks mean less frequent top-ups and more stable nutrient strength. For small setups (under 10 pots), 100L covers it. Larger rooms scale up.
Flood cycle management
The tank works with IWS control brains (basic, standard, or pro models). The Pro uses a single 4000lph drain pump, so the FlexiTank comes with one drain hole. Set your flood times on the brain, keep nutrient levels topped up, and check EC and pH weekly. The recirculating nature means your solution stays stable.
Light proofing
The zippered lid is 100% light proof, preventing algae growth in your reservoir. Algae kills oxygen levels and destabilises your nutrient mix — this lid solves that problem outright.
Pipework compatibility
Connect using 13mm or 25mm flexi pipe depending on your IWS brain variant. All holes are reinforced to handle pressure without splitting.
Technical specifications
-
Available sizes: 50L, 100L, 225L, 400L, 750L
-
50L dimensions (assembled): 35cm diameter × 53cm height
-
100L dimensions (assembled): 43cm diameter × 78cm height
-
225L dimensions (assembled): 63.5cm diameter × 81cm height
-
400L dimensions (assembled): 68cm diameter × 111cm height
-
Material: Thick, waterproof flexible fabric with reinforced pipe/tap holes
-
Support structure: Five fabric-slotted support legs for vertical stability
-
Lid: Full-length zip closure, 100% light proof
-
Drain configuration: One drain hole (compatible with IWS Pro Remote Brain 4000lph pump)
-
Pipe compatibility: 13mm and 25mm flexi pipe fittings included
-
Folded storage: Packs flat like a tent for easy transportation and storage
Who this is for
- Growers already committed to IWS flood and drain systems looking to upgrade or replace their reservoir
- Loft and small-space growers who can't justify rigid tanks they can't store
- Anyone scaling their ebb and flow setup and needing extra capacity without permanent fixture costs
- Growers prioritising reliability and UK-made quality over budget plastic alternatives
- Experienced flood and drain users who know what they want from a reservoir and don't need hand-holding
Not ideal if you're starting hydro from scratch and don't already own an IWS brain — you'll need the pump and control unit separately. But if you're already in the IWS ecosystem, this is a no-brainer.
Our take
This is a properly engineered bit of kit. IWS have been refining flood and drain for years, and the FlexiTank design reflects that — it's tough, it works, and it doesn't pretend to be anything other than what it is.
If you're running IWS flood and drain and need to add tank capacity or replace a rigid reservoir, worth picking up while stock lasts. Does exactly what it should, and it'll outlast most of the other stuff in your grow room.
