Rainwater Harvesting FAQs
Can I get any grants or tax allowances for installing a system?

At present there are no funding directly aimed at rainwater harvesting. It does however qualify for 100% capital allowance relief on commercial premises.

How much does it cost to run the pump?

It typically takes 1.5- 2.0 kWh to pump 1 cubic meter of water (1000 litres). For a typical house using rainwater for WCs, washing machine and the garden, pumping costs are between 5-10p per week.

How often does a system need topping up with mains water?

A well designed system with a good match between supply and demand will only need topping up when it has not rained for some time.
Severn Trent monitored a domestic system and found that it only occasionally needed to be topped-up. Most of the time the tank was around 50% full (ie, an ideal balance between having plenty of water to use, and plenty of space to accommodate the next rainfall).

How long will a Rainwater Harvesting system last?

The buried components, indefinitely. Components such as the control system, pump and filter have an extremely long working life, and are easy to replace should the need arise.

What maintenance is required?

Typically, washing off the filter (5-minute job with a garden hose) once a quarter is all that is required.

Is there a danger of Legionella?

No, the system does not provide the conditions necessary for the cultivation of Legionella. With the water stored underground it is dark, cool and is kept well oxygenated. Legionella cannot cultivate in these conditions.

Is Rainwater Harvesting only for new builds?

Systems are best designed-in from the outset, but can be retrofitted depending upon the accessibility of pipe work.

What happens during a dry spell?

When there is insufficient water in the storage tank the rainwater harvesting system automatically draws water from the mains so that, from the point of view of the user, no difference is apparent.

Can I drink the RainWater?

In the UK, rainwater is not usually harvested for drinking purposes so it is therefore not normally recommended.

Is the Rainwater clean?

The tanks have filters that remove all debris and particles from the water, so that the water remains clear.
Please note that, in the UK, rainwater is not usually harvested for drinking purposes so it is therefore not recommended.

Can I use normal detergents and cleaners and will they affect my plant's performance?

Yes, normal domestic use of these products is acceptable to the plant biology.
If higher than normal quantities are expected, you should contact Harlequin before purchase.

How much electricity does the plant consume?

Septic Tanks do not utilise any power.
6 population plants such as the Hydroclear utilise 60-80watts, similar to that of a light bulb.

Will paper towels, sanitary towels, etc, clog up my system?

Sanitary towels and similar non-biodegradable products should not be flushed into any wastewater treatment products.

Does the plant make a noise?

Modern compressors are virtually silent, contained within housings further reducing noise levels.

What distance from the property does the plant need to be?

A minimum of 7m should be used, increasing to 25m if serving more than one building.
Some local authorities will permit significantly closer installations if it is as far as is practicably possible.
Your Building Control Officer should always be consulted early in the planning stage regarding the location of the treatment plant.

What is the difference between a silage tank, a septic tank and a treatment plant?

A silage tank or cesspit collects and stores all of the raw wastewater and has to be emptied when full. These are not permitted in Scotland. A septic tank physically separates the solids from the liquids; the liquid is allowed to flow out of the tank, usually for dispersal by a network of underground perforated pipes called a soakaway. A treatment plant works like a septic tank but has an additional stage to treat the liquid removing the dissolved constituents. The quality is then sufficient for direct discharge to surface waters.

Will a soakaway drainage system become blocked up after several years of use?

If the soakaway system is laid properly according to the percolation test and BS 6297:2007, it will last for many years.
Organic matter can eventually build up with the distribution network so it is therefore important to recognise that a soakaway system will not last forever.
Proper maintenance and desludging of the tank is the most important factor in maximising the life of the soakaway.

My septic tank/treatment plant smells. Why is this happening?

The most common reasons are incorrect venting arrangement, a lack of maintenance or incorrect operation.
The wastewater tank as well as the drainage pipes need to be sealed, venting to an appropriate dispersal point. This includes sealing all access points in the drainage pipes and u-bends on pipes in the dwelling.
Maintenance and correct operation (use of detergents etc.) is vital to ensure that the system is physically and biologically treating the wastewater correctly.