WaterMate : an automatic solar polytunnel watering system

Harvst WaterMate Pro is a solar watering system for polytunnels up to 40 metres squared, using dual zone system for drip irrigation, misting, drippers, sprayers or soak hose.

It’s a solar watering system that needs no mains power : 100% off grid.

The powerful pump means you don’t need a tap or garden hose, so it can run anywhere you have a water tank. If you have a tap, just leave out the pump.

It’s smart, and saves water. It won’t water when the soil is moist, and can water extra when you plants need more. It monitors your soil moisture, tracks temperature and coupled with a timed system, delivers just the right amount of water to your plants.

It’s app controlled, and if your polytunnel is within range of a WiFi network, you can manage and monitor from anywhere, and even receive email alerts.

Solar powered

WaterMate is powered by a built-in battery, charged by a solar panel, which means you can run it anywhere there’s sunshine.

The solar panel just needs to be mounted where it gets the most amount of sun. It’s provided with adjustable brackets which will screw to a timber frame, or to a wall or fence.

The solar panel is approximately 230*185*15mm in size.

Use a water tank …

You can water your polytunnel automatically even if it’s nowhere near a tap; all you need is a water tank nearby. The powerful pump will deliver up to 17 litres/min at 35psi (more than mains water pressure).

… or a tap

If you have a water tap in or near your polytunnel, you can connect it directly to the dual zone water valve and leave the pump out.

Efficient with water

Using a combination of sensors (heat, light, and optional soil moisture), WaterMate can change the watering regime based on the conditions in your polytunnel.

On a hot day or when the soil is dry; more water – so your plants don’t suffer.

On a cool day, or when the soil is already damp; less water, to make your tank last longer.

WaterMate is a versatile, modular system which fits into almost any greenhouse or polytunnel. It’s made up of some core parts:

  • Control unit with battery
  • Solar panel
  • Dual zone water valves
  • Pipes and sprayers

A garden hose will fit the water valves with a standard snap-on connector. If you are using a water tank, then you need:

  • Main water pump

Extra sensors (optional):

  • Air temperature / humidity sensor
  • Soil moisture sensors
automated mini greenhouses uk

An app controlled smart watering system

WaterMate settings are managed via a free web app which runs on iPhone, Android, even your laptop computer. This lets you choose exactly what watering settings you want, for each of the two zones.

Also included with the Harvst control app is an interactive garden journal, so you can record what you’re growing, get reminders for re-sowing, and learn more about what you can grow in your polytunnel.

Email alerts keep you in touch

If your polytunnel is within range of a WiFi network, WaterMate can be set up to send alerts to your email when your polytunnel gets too hot (open the door!), too cold (get the fleece out!), too dry (turn on the water!), or if the water tank has run out (top it up!).

What's the capacity of our polytunnel watering system?

WaterMate can power two separate zones (or 3 zones with a second pump). Each zone could be:

  • 30m of soak hose
  • 60 x drippers
  • 20 x sprayers or misters
  • A combination of drippers, sprayers and misters

A sprayer nozzle can typically cover up to 1 metre squared. With a full capacity of 40 sprayers, that’s 40 metres squared of soil. Alternatively, one dripper per plant (eg tomato) means a capacity of 120 tomato plants.

Polytunnel drip irrigation system

Supplied with a range of sprayers / misters

WaterMate is supplied with a range of industry standard 4mm sprayers for you to experiment with and learn what works best for your polytunnel. Extra sprayer nozzles are available via our online shop.

Greenhouse irrigation system

The sprayers can cover up to 1 metre squared, great for salads, spring onions, seedlings and much more.

4mm irrigation sprayers are available in 90 degree, 180 degree and 360 degree versions, as well as different flow rates.

The 4mm micro irrigation emitters are a direct push-fit into the supplied LDPE distribution pipe.

If you put a sprayer in the wrong place, or want a different layout next season, use 4mm ‘goof plugs’ to plug the hole.

What makes a good polytunnel watering system?

Polytunnel automatic watering can be done in a number of different ways, ranging from overhead misters, to soak hose embedded in the soil, to individual plant drippers and dripper lines. You’ll have different plants growing in different areas of the polytunnel that each need watering in different ways, at different stages of their growth, too. Here’s a way to approach the challenge.

A versatile foundation

You probably don’t want to be setting up your polytunnel watering system from scratch every year, so put the foundations in place which you can modify each season, and throughout the season as plants change. Typically this involves distribution pipes, from which you take off the type of watering you need. 13mm LDPE hose is what we recommend for common small to medium sized domestic polytunnels; you get enough water flow through the pipes and they are not too cumbersome to manage.

A range of outlets / emitters

Your salad might want misting or spraying. Your tomatoes would prefer drip feeding or bottom feeding. A tray of seedlings would like a combination of spraying and bottom watering. A perfect automatic polytunnel watering system will need to deal with all these situations.

The Harvst WaterMate Pro has two separate watering zones, which helps with the first level of separation. You can have one zone for distributing water around your polytunnel to dripper lines, and the other zone for spraying and misting. With taps in suitable places, you can choose which physical areas in your polytunnel get misted, and which get drippers.

A high flow rate

Polytunnel watering can consume a lot of water, so whatever automatic watering system you use you’ll need to make sure it can provide enough flow to supply all the outlets you are using. The smaller, high pressure pumps used in many plant self watering systems simply don’t provide enough flow for a larger area. You’ll get some water to the first few outlets and then the rest will be dry. The 3 gallon per hour pump supplied with the WaterMate pro will feed up to 60 outlets per watering zone at a good flow rate.

Good water pressure

Flow rate isn’t all you need. You’ll need the pressure to push water through all the pipes, up into the roof, and deal with the long pipe runs encountered in a polytunnel. A small, camper-van style pump might claim 15 litres per minute, but when you connect it to a long pipe system, it won’t have the pressure to get the water through.

Solar powered

Most polytunnels don’t have mains electricity available, so any automatic watering system for a polytunnel will need to be solar powered. Coupled with the need for a powerful pump which draws significant current, this doesn’t leave you with many off-the-shelf options. Your solar generating capacity will need to match or exceeed your pumping power drain – even better if the automatic watering system can monitor your battery capacity and adapt the automating watering appropriately.