Rainwater Overview

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How do I make the most out of my rain water

Connecting your tank to the whole of house creates by far the most water savings.

A diverter box is placed on the house side of the water meter and when the tank contains water it is used, when the tank is empty scheme water is used. The big advantage to whole of house is no internal plumbing needs to be changed.

Can I use it in the toilet and washing machine

You can use the water in your toilet and washing machine, this requires separate plumbing to these areas so is comparable in cost to a whole of house system. You will make more water savings than just using it for the garden but less than whole house.

Using rainwater over winter when it rains is the key to high water savings

Zincalume under eaves tankCan I use rain water to water my garden

Sure but it probably won’t last the summer. Perth’s rainfall mainly happens between April and October, given that you don’t collect the first 2mm of rain, your tank is unlikely to refill outside of these times. It would be sufficient for hand water some pots and maybe a small courtyard.

How big a tank do I need

We recommend a 3000L tank for autumn, winter and spring seasonal use to get the most water savings for your investment. Due to Perth’s rain fall pattern you will get the biggest water savings if you use the water over winter when it is raining. A 3000L tank will stay full over winter and can supply all your water needs for 5 months of the year provided you are ‘water wise’. A larger tank may only give you another few weeks. Ask to look at our calculator when you have your initial consultation or download a copy of the excel file.

How much is a water tank

The tanks themselves are less than ½ the cost of a rain water catchment system; unless of course you are putting a small tank under a downpipe with a tap. You need to include the cost of a pump, filters, plumbing, collecting and getting the water to the tank, a diverter, over flow into a soak well, first flush value, power for the pump and labour for digging all those trenches. Refer to budget estimates.

What is a wet system

A wet system simply means there is water always in the collection pipes; we always use lead free pipes, standard storm water pipe contains lead. Down pipes are connected to a ring main that runs around the house, provided the inlet to the tank is below the gutter height, gravity feeds the water into the tank.

A Dry system

In a dry system the downpipe is fed straight into the top of the tank; often used for smaller tanks.

Is rain water safe to drink

For many people, rain water is their only source of clean drinking water. Provided appropriate steps are taken to seal the tank and the water is filtered there is minimal risk to human health. All commercially available tanks sold in Australia conform to standards to ensure they are safe. Tank water is free of added chlorine and fluorine!

What filters do I need

There are several different filters at different stages.

  1. Leaf catcher – first line stopping large >2mm objects getting into the system
  2. First Flush – diverts dirty water into the soak well
  3. Disk/mesh filter – water passes though a stack of disks or mesh which act as a strainer, it removes particles >200 microns, sits after the pump at the tank
  4. Cartridge filter – fine filtration down to 0.5microns removes parasitic cysts, often incorporated in with the disk filter.
  5. UV treatment – Kills the micro organisms in the water
  6. Carbon filter – removes VOC’s, chlorine and sediment. This is the same type of under sink filter many households on scheme water use.

In general we install filters as per above # 1 to 4 on every job, the last 2 are up to the client.

I have read you need to have a UV filter

The Health department recommend you have a UV filter, it is only a recommendation. For single residential use it is totally up to you. 

Leaf catchers

Often left off by unexperienced installers, leaf catches stop leaves and small animals from entering the tank. They can sit at each downpipe or just before the tank inlet and need empting occasionally. One of the main issues with water tanks is parts clogging with leaves; a leaf catcher will circumvent this problem.

What is a first flush valve

Your roof gets covered in dust and pollutants over summer, the first time it rains it is all washed away into your tank… this is where the first flush value comes in. We recommend you leave the valve open during summer so all that dirty water is washed into your soak wells, after the first rains in autumn close the valve so all the clean water enters your tank.

Pumps

There are 2 basic types of pumps, ones which start every time you turn a tap on and ones which have a pressurization unit. The pumps we use hold around 8L of water under pressure so when you turn the tap on for a short period of time the pump does not need to come on. This saves electricity and increases the life of the pump. We only use quality European pumps. Ensure you have a power point close to where your tank is going when you plan your house.

Round tanks vs. Oblong tanks

Round tankBased on a straight price comparison a round tank is about half the price of an oblong or under eaves tank. This is because a circle is very structurally sound and requires no internal engineering to make it strong. An oblong tank has internal struts and is highly engineered to make it structurally sound.

Looking at it from a more holistic view point a round tank may not be the best option. A round tank needs a sand pad, a large area and can be hard to get onto site. If you need a crane to lift it over your house there goes any money you saved. An oblong tank can fit through small spaces and sit neatly under your eaves out of the way, these are very popular and often the only option.

What about underground tanks or water bladders

Underground tanks can get quite pricey and unless you are really short on outdoor space probably not the go for most people. The advantage of an underground tank is you can use the area over the top of it as living space. Water bladders are placed under a house sitting on stumps where the floor is raised above the ground. These haven’t really taken off in Perth due to our preference for slab on ground construction.

Metal or Polyethylene tanks?

All tanks, regardless of external material have a food grade poly lining. Polyethylene tanks are moulded in a single piece so they have no seams or joins; there is a wide range of styles, shapes and colours from the many different manufactures. Metal tanks are made from BlueScope steel and lined with Aqua-plate polymer film; they come in round or oblong and can be custom made to your exact requirements. Which is better – it really comes down to the look you want.

What about concrete tanks

Concrete tanks are mainly used for large scale underground tanks, for farms and commercial situations. They became cost effective for tanks over 10KL.

Will I need to modify my downpipes

Your down pipes need to enter the stormwater pipes above the height of the tank inlet, we can connect a down pipe at the down the bottom but they tend to leak and we prefer not to. When we work with a builder on a new house we will instruct the builder to not install down pipes and we will do those ourselves. We use 75mm round pvc downpipes that can be painted to suit your walls.

Do I still need soak wells

It is illegal to allow any storm water from your property to leave it, yes it is very illegal to empty your swimming pool into the storm water system. You must provide soak wells under paving, for down pipes and for water tank overflow. If you have existing soak wells we may be able to connect into it, otherwise we will have to install a soak well. Your water tank will probably overflow a few times over winter.

 

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