Optimising Tank Water Delivery

How to reduce your water pumping costs

Rainwater tank systems that are plumbed-in often use a pump to deliver mains-pressure flow, for household or garden use. Typically, the pump will be running at full power irrespective of the flow rate it's delivering, even if flow is restricted as in the case of filling a toilet cistern.

When used to water a garden there is usually no need to restrict flow. However, the fittings used in the delivery system may cause a significant reduction in flow rate. This may result in you taking more time to water your plants, and may also result in higher power costs due to your pump having to run for longer.

The first things to do to ensure your tank water delivery system is optimised is to ensure you install appropriate size piping from your pump to outlet or tap. A rough guide is to match the pipe size to the outlet of your pump. In my case the pump has a 1" outlet and I've used a 1" pressure pipe.

The next thing to look at is the size of the delivery system, starting with the tap itself. Conventional washer-type taps have a slightly convoluted construction, whereas ball valve taps provide a noticeably better throughput due the the straight-through flow of water. An additional bonus for garden watering, where I generally always want maximum volume, is the ball valve is fully open with just a quarter turn. Quick and easy!

Hose pipes are generally 12mm or 1/2", however 18mm versions are also available. The benefit here is they have more than twice the area of the the 12mm hosepipes, meaning lower velocities and therefore lower losses in transfer. However, note that the hose may  well be fitted with 12mm fittings, as these are the common fittings provided with most taps and hoses. To get the maximum benefit from your larger hose, dump these and get the 18mm fittings for the hose and tap.

The final element of the delivery system is the watering nozzle. You can get high flow units ready-fitted with 18mm connectors. Or, in my case, I drilled out my existing trigger gun to maximise the flow.

From a maintenance perspective, ensure that you clean the inlet filter. Due to the organic material that ends up with the collected water, these filters can get quite clogged. 

Removing these every month or so and giving it a good clean will ensure a good flow of water into your pump. The effect of a clogged filter will be most pronounced when your tank levels are low, resulting in very little pressure out of the tank.

Enjoy reduced energy watering with your pimped rainwater delivery system!