The Dutch who grow everything using this system, have mastered this technique. Nor do they just grow everything, they grow on an unprecedented scale compared to any other nation. The plants are propagated in a rockwool cube then grown on in a rockwool slab. The plants are individually fed using drippers. These drip emitters are designed to deliver at a set rate at a pre-set volume of water per hour.

Each dripper is wired to an infrastructure of tubes and delivery pipes, which are fed by one master pump. Most commercial systems are what are known as high-pressure drip systems and most domestic systems are known as a low-pressure drip system. These commercial high pressure drip systems are typically run to waste systems. This is when the nutrient is bled off and after dripping through the rockwool slab then simply allowed to run down the drain i.e. to waste. This ensures these plants get the exact maximum nutritional value from the nutrient solution and also cuts back on the possibility of bacteria or fungal problems like pythium. Most low-pressure drip systems are recycling or re-circulating systems where the nutrient returns to the tank then gets pumped back to the plants, then to the tank, so on and so forth.

These systems are relatively cheap compared to others and easily built once you get your head round the spaghetti of pipes, tubes and fittings. Drip systems are also very versatile and can be made in many shapes and formats allowing you a more modular design for your grow rooms.

The running costs of these systems are not cheap as after each crop you basically dispose of the rockwool slab and replace it with a new one. A 1 metre slab normally holds approximately 3 plants which can run up quite a bill if you have many plants. Also if you are running to waste then the cost of nutrient is very expensive indeed.

The main draw back with these systems is that the dripper can clog. Similar to the NFT system, if a dripper stops your plants will suffer. If you fail to notice that a dripper has stopped the plants runs the risk of dying or at least losing its potential to give good yields. These systems need constant maintenance and up keep and are not recommended for the beginner. All drip irrigation systems are a little tricky to maintain, as you need to take constant pH and CF readings from your tank, from you run off and from your rockwool medium. This process is achieved by using a syringe to suck up a sample from inside the rockwool where the plants are growing. As the medium itself will hold a different pH and CF value to the tank and indeed even the run off. Then armed with this info you need to re adjust the system again and do all those tests once more until you are happy that you have the right levels that you require. This process can easily need doing once a day. It is also advisable when growing in rockwool slab culture to flush the salt out every 2 weeks with pH adjusted plain water. This needs to be done as rockwool tends to absorb unused salts which can build up, therefore need flushing every 2 weeks or so. It is also advisable to do this flushing out process to flush out any salt build up that can concentrate in the drippers. Regular flushing can alleviate some of the maintenance problems of these systems. However getting blocked drippers is part and parcel of this system so it is always advisable to clean them regularly and also to have ample spare drippers to swap when old drippers need cleaning.

The above to one side, this is a very productive hydroponics technique and has served the Dutch very well. The rockwool slab does offer a lot more support that you would achieve if you were using NFT systems. It also is less prone to pump failure and as the slabs absorb a lot of water you do have some breathing space if the pump or drippers fail. It is very detachable and modular allowing easy expansion or removal of the system. Low pressure drip systems are more prone to dripper failure compared to high pressure drip systems however for Percy Throwers, the high pressure option is too expensive and industrial for a small indoor garden.