Multitank Rainwater Wall Tank: 500 Litres in Two Wall-Mounted Tanks

The 2 x 250 Litre Multitank Rainwater Wall Tank is a pair of slim tanks that hang against an outside wall and fill from a downpipe, giving a combined 500 litres of stored rainwater without taking up the footprint of a conventional water butt¹. Each tank measures 790mm wide, 380mm deep and 1050mm high, so the pair runs along a wall rather than out into the garden¹. For a household getting ready for a dry spell, a hosepipe ban or a supply interruption, that is a useful reserve for the garden and for non-drinking uses, kept off the ground and out of the way.

The kit arrives ready to install, with a downpipe filter, a tank to tank connector and a filter to tank connector, plus ¾-inch threaded connections on both the front and the back for taps or hose fittings¹. It is designed to be expandable and a connector is provided, so you can add capacity later¹. The maker recommends emptying the water in the tanks during the winter period, and fits a side outlet for thorough drainage before frost sets in¹.

This page covers what the kit includes, its size and capacity, how it connects to your downpipe and to further tanks, and how to look after it through the year. It is one option among several for storing rainwater at home; the wider choices are set out in Rainwater Harvesting at Home: How a System Works.

What the 2 x 250 Litre Multitank kit includes

The kit is supplied as two tanks with the parts needed to link them and to take water from a downpipe. The maker lists a downpipe filter, a tank to tank connector and a filter to tank connector, and describes the set as ready to install¹. The downpipe filter is listed as an option chosen above, so check which filter you have selected when you order¹.

The tanks come in anthracite or concrete-gray finishes, and the front faces are textured with two motifs, stone and slate, so the pair reads as a wall feature rather than a pair of barrels¹. Each tank has ¾-inch threaded connections on both the front and the back for taps or hose fittings, and a side outlet for draining¹.

• Downpipe filter: keeps leaves and grit out of the stored water before it enters the tank¹
• Tank to tank connector: joins the two tanks so they fill and draw as one body of water¹
• Filter to tank connector: carries filtered water from the downpipe into the first tank¹
• Front and back tappings: ¾-inch threaded, for a tap or hose fitting¹
• Side outlet: for emptying the tank completely before frost¹

A filter is not a luxury on a rainwater tank. Water that sits with leaves and grit in it is harder to keep clean, and the maker's own guidance on tank care is to clean and disinfect any tank before you draw water from it². The filter reduces what gets in; it does not remove the need to check and clean.

Capacity and size: 500 litres in two 790mm wide tanks

The pair holds 500 litres in total, 250 litres in each tank¹. Each tank is 790mm wide, 380mm deep and 1050mm high¹. Side by side that is a run of 1580mm of wall, standing a little over a metre tall and projecting 380mm from the wall before you allow for the downpipe, filter and any tap or hose on the front¹.

What 500 litres means in practice depends on what you ask of it. It is a garden and outdoor reserve, not a household water supply. The maker's wall tank collection ranges from 250L to 1000L, so this pair sits within that range, and the biggest rainwater tanks described in the guidance can hold over 1,500 litres². If you are working out how much storage your roof and garden actually justify, the method is set out in How to Size a Rainwater Tank: Roof Area, Rainfall and Demand.

The depth matters as much as the width. A tank standing 380mm off the wall needs a clear path in front of it for you to reach the side outlet and the front tap, and it needs a wall that can take the weight of a full tank. Fixings and the wall itself are the installer's responsibility, and if you are unsure what the wall will carry, take advice before drilling.

Connecting the tanks to a downpipe and adding more

A wall tank is a space-saving rainwater storage solution designed to connect to your home's downpipes³. The principle is simple: the downpipe is cut, the filter is fitted in line, and filtered water runs into the first tank. The second tank is joined to the first with the tank to tank connector so the pair fill together¹. When the tanks are full, the surplus has to go somewhere, and on the maker's larger tanks an overflow siphon diverts excess water to a drain or soakaway⁴. Plan that route before you fit the kit, so overflow runs away from the wall footing rather than down it.

The maker's guidance is that you can join multiple tanks together, and all you need is a connection kit³. The tank is designed to be expandable and a connector is provided¹. The same approach is described across the maker's range: multiple tanks can be connected in series to increase capacity by linking tanks through simple connection kits⁵.

• Before you cut: check the wall, the fall of the ground and where overflow will go
• Fit the filter: in line with the downpipe, feeding the first tank¹
• Link the tanks: tank to tank connector between the two¹
• Add a tap or hose fitting: on the front ¾-inch connection where you can reach it¹
• Add more later: a connection kit joins further tanks³

There is a wider reason to fit a butt or tank on a downpipe. Official drought advice recommends installing a water butt for rainwater storage from your downpipes, which can be connected to greywater systems such as toilet flushing and garden watering⁷. Independent guidance on summer flooding makes the same case from the other direction: water butts on downpipes collect and store rainwater, reducing runoff and pressure on drainage systems⁸. A wall tank does both jobs, holding water back from the drains when it rains hard and keeping a reserve for when it does not.

Set it up while rainfall is plentiful so it is ready when dry spells arrive, and remember that butts can be linked so excess water flows automatically from one to the next⁹. If you are connecting to a downpipe for the first time, the steps are set out in How to Connect a Water Butt to a Downpipe, and the filter choices in Rainwater Filters: Downpipe, Inline and In-Tank Types.

Empty the tanks before frost sets in

The maker's instruction is plain: it is recommended to empty the water in the tanks during the winter period¹. The side outlet is included for thorough drainage before frost sets in¹. Water left standing in a full tank through a hard frost is the main avoidable risk with any outdoor storage, and the maker has designed this kit to make emptying straightforward.

Make it a routine rather than a rescue. Drain the tanks through the side outlet, routing the water away from the wall, and close the outlet again afterwards. The same seasonal discipline applies to water butts across the garden: empty any water butts before the rain starts to reduce the rainwater flow into the drains when a storm arrives¹⁰. That advice comes from water companies preparing customers for storms, and it is worth following for two reasons at once: it protects the tank from frost and it takes pressure off the drains when the next storm lands.

Insulation advice for tanks is mostly written for indoor cold water tanks in lofts, and it is worth knowing the difference. All storage tanks must be insulated to guard against freezing during the winter and excessive warming during the summer months¹². Wrap up your pipes and water tanks with lagging, especially those in unheated areas such as lofts, garages or gardens¹³. But do not insulate beneath water tanks in the loft, as this prevents warm air from the rooms below reaching them and could cause freezing¹³. For an outdoor wall tank, lagging the exposed pipework and fittings is sensible; the tank body itself is emptied for winter on the maker's advice¹.

If you are leaving the house empty for a few days, close the stop tap and drain the system so there is no water in it to freeze¹⁶. If you are away only briefly, keep the heating on low if you can¹⁷. These steps protect the plumbing inside the house; the wall tank is dealt with separately by emptying it.

Keeping the water clean and the tank working

Stored rainwater is for the garden and for non-drinking uses unless it has been treated. Check the filter through the year, clear leaves from the downpipe and the filter body, and look inside the tank for sediment. The maker's maintenance guidance for its systems is set out in Keeping a Rainwater System Clean and Working Through the Year, and the question of what the water can safely be used for is covered in What Harvested Rainwater Can Be Used For in Your Home and Garden.

The tanks are made from high-quality material resistant to UV rays and harsh weather, making them durable outdoors¹. That covers sunlight and ordinary weather. It does not make the water inside immune to going stale in a long warm spell, and it does not remove the need to drain before frost¹. If you want to know whether stored water deteriorates, Does Stored Rainwater Go Off or Stagnate? answers it directly.

• Before winter: empty the tanks through the side outlet¹
• Before drawing water: clean and disinfect the tank²

Support, delivery and where the kit fits a household plan

The product is delivered on a pallet by a haulier, and the maker asks you to advise of any access problems by calling 01733 405111¹. A pallet needs somewhere to be set down, so a narrow lane, a locked gate or a steep drive is worth flagging before delivery day. The same number reaches the sales team on option 1, and the maker runs a full-time, fully trained technical help desk to answer questions from clients, builders and plumbers before, during and after the install¹⁸.

For a household building a water reserve, this kit does one job well: it stores 500 litres against a wall, out of the way, and it can be expanded with a connection kit¹. It is not a substitute for stored drinking water. Keep a separate supply of drinking water for an emergency, as set out in Water in an Emergency: A Household Guide, and treat the wall tank as the garden and outdoor reserve.

The maker's brand page is at Multitank. If you are weighing a wall tank against a conventional butt or a buried tank, the trade-offs are set out in Water Butts: Sizes, Fittings and Where to Put One and Above-Ground Rainwater Tanks: Vertical, Horizontal and Slimline Types.