Rainwater harvesting is becoming popular once again among farmers and home owners as the introduction of water charges starts affecting more and more people.

Harvesting rainwater is not a new phenomenon, however. It has been taking place on Irish farms for centuries. Many rural farm households had a rainwater tank that collected the run-off from the dwelling house and livestock sheds, which served as a means of drinking water for livestock.

It was also a valuable water source for domestic purposes in the farmhouse. In the past, a reservoir of rainwater at a person’s back door was a great asset. In many instances, the alternative was travelling miles to the community hand pump to source water and carry it all the way back again. But, with the introduction of mains water supplies and automatically pumped private wells, the water tank at the back door became redundant.

Today, rainwater harvesting is becoming popular once again among farmers. This time, it’s not for convenience reasons but, rather, a cost saving exercise. Water supplied by the county council is no longer free and has been the case on many farms, even before the turbulent introduction of Irish Water.

I recently visited a dairy farmer in Co Laois, who has started harvesting the rainwater from his livestock sheds. He had an old concrete tank, which was used for this purpose years ago, and he got it back up and running this spring. The water harvested into the tank is now used for supplying water to the paddocks, cubicle sheds and washing down the parlour and collecting yard after milking.

The main reason the farmer decided to get the system back up and running was to avoid wasting the water coming from the roofs of the sheds.

Picture one

This is the 15,000-gallon (68,191-litre) capacity tank that the farmer had in his yard. It is over 30 years old and is built from shuttered, poured concrete. The farmer stopped using this tank because it started leaking over 10 years ago. He had a number of large sheds close to the tank and felt that the water coming from these sheds could be put to use for cleaning down the dairy parlour and collecting yards.

The farmer contacted Martin Campion, from Campion Pumps, to see how the rainwater could be used efficiently. Martin designed a system that allowed the water to be harvested from the roofs, but also a way of recycling the well water used for cooling the milk in the plate cooler.

The advantage of this system was that the farmer hadn’t to go out and buy a new water storage tank. He just used the one he already had by repairing the cracks. Where a concrete tank like this is not present, Martin says some people use old milk tankers or buy in precast concrete or plastic tanks.

Pictures two and three

Over the years, due to settling and hard frosts, some considerable cracks started to appear in the walls of the old storage tank (similar to the cracks in picture two), which allowed water to leak. This left the tank useless. However, the farmer hired the services of Billy McEvoy, from Oldtown Construction Ltd, who uses a new system for sealing cracks in concrete.

Along the side of the cracks, Billy drilled a series of holes at an angle into the centre of the cracks. Injection ports were screwed into these holes. The injection ports had grease nipple heads on the ends. A polyurethane resin, Webac 1403, was then pumped into the cracks using a normal grease gun until the resin started to appear on the outside of the crack. The grease nipple end is then screwed off the rest of the port. As it is screwed off, a rubber valve inside the injection port closes, sealing all gaps. Since then, there have been no water leaks in the tank. This is a reasonably new system and it could definitely solve a lot of problem cracks in silage pits and slurry storage as well.

The resin has a very low viscosity and can work its way into cracks down to the size of a strand of hair. When it comes in contact with moisture, it expands, pushing water out of the crack and sealing it permanently. The cost of the Webac resin is approximately €15/litre. The amount used obviously depends on the size of the cracks. Sometimes, there may be many more cracks inside the wall that you can’t see, which will use up more resin. Construction Chemical Supplies in Dublin supply this special sealant resin.

Pictures four and five

Water comes from the roofs of the sheds and enters the leaf and debris trap. This trap stops the leaves and debris from entering the tank and allows rainwater to flow down through the filter. Martin Campion says it is very rare that the trap will ever block because, when it stops raining, the leaves will dry out and crumple up. When the next flow of water comes after rainfall, the leaves are light enough to be pushed out of the exit.

Pictures six and seven

The tank is topped up by water from the farm well. A float valve regulates the level of the water in the tank and if it falls under a certain level, the well water comes into action.

From the tank, water is pumped to water troughs in the paddocks and the sheds using a regular Lowara pump. Gravity feeds the water from the tank to the dairy parlour. Here, a washdown pump helps to increase the pressure for washing down the parlour.

“The more pressure you have, the less volume of water you use and it means you will get the job done quicker,” explains Martin.

Picture eight

This is the plate cooler on the farm. Martin says he sees lots of farmers wasting valuable water in plate coolers because, once they are turned on, the water is let down the drain.

With this system, the water for the plate cooler comes from the well because well water is the coldest water available.

Once milking starts, the plate cooler is switched on, allowing the well water to circulate through the cooler but rather than letting it down the drain, it is piped back to the water tank and mixed with the rainwater.

Click here to download the diagram in PDF format

How it works: rainwater harvesting system

A. Water comes from the eave runs and enters the water tank. There is capacity for 15,000 gallons and if the amount of rain exceeds this limit, the excess water overflows.

B. In times of low rainfall, the tank is kept topped up by a well on the farm. A float valve regulates the amount of water in the tank and keeps a minimum reserve of 10,000 gallons in the tank at all times.

C. The well water is pumped directly into the plate cooler. When it finishes its job in the plate cooler, it continues on to the water tank, where it can be recycled.

D. Water from the tank is pumped to a loop system to service the troughs in the paddocks and it also services the troughs in the sheds.

E. The tank water is used for washing down the parlour. The pressure in the water is increased using a washdown pump.

Comment

In midsummer, this farmer uses over 5,000 gallons of water each day to wash down the parlour after milking his 170 cows and to service the paddocks.

If he was relying on metered council water, it would cost him over €30/day. For farmers depending on council water, no matter what size they are, water harvesting provides a real cost-saving. For dairy farmers using big quantities of water, a tank like the one this Laois farmer has is a valuable reservoir in case a well pump breaks down.

A rainwater harvesting kit, including a pump, transfer system, leaf and rodent filter, and calming inlet, costs in the region of €2,500. Every system is different and will have different requirements. Washdown pumps and pumps to troughs cost in the region of €1,500 to €4,000, depending on specifications. Where there is no existing water tank, you can buy a reservoir for water storage at a cost of between €7,000 and €10,000, depending on volume and whether you go for a concrete or a rubber-lined steel tank.

The Webac resin, supplied by Construction Chemicals in Dublin, used for blocking cracks in concrete was impressive. It will be covered again in future articles.