The following information has been researched and prepared by
​Budyong Hill Chair of the Renwick Smart and Connected Water Working Group

Water tank installation – Pros and Cons prepared January 2020.
 
There have been questions asked about the pros and cons of installing water tanks in Renwick, especially with the decision to have water meters. Before considering this option people need to be aware of issues regarding use of rainwater from tanks. The main consideration is whether people wish to use rainwater for household use only or also for the garden.
 
Irrigation with a sprinkler can use up to 1,000 litres of water/hour. This is a lot of water when you consider that an average water tank for a standard residential section might hold 5,000 litres. This amount of water will last considerably longer for household use than for irrigation. We have a 4,000 litre tank and use water regularly for household kitchen use plus for watering seedlings etc in the garden using a bucket. This size tank provides us with plenty of water year round for this sort of use. People with large sections may have room for bigger tanks.
 
We will have to wait and see what the final volumetric charge will be for water used over the 200M3 (cubic metres) annual allocation per household. It was proposed to be $0.66/M3. For a 25,000 litre water tank that is 25M3 x $0.66 = $16.50. Current online price for a Baileys 25m3 tank is $3,300. When you take the costs of setting up a large water tank or tanks for irrigation purposes including a pumping system to provide pressure and the ongoing running and maintenance costs of the pump it's clearly going to take a long time to get a payback on your investment. We as a community have made the decision to upgrade our water system knowing our water costs are going to increase to cover our contribution for financing the investment and knowing our return for that increased cost is a reliable, safe water supply. The logical thing for a consumer to do is use that supply because that is the way to get a return on their share of paying for the investment rather than invest in water tank/s and a pump. Likewise for MDC, the decision has been made to make a large investment in upgrading Renwick's water supply with 50% of capital costs coming from reserves. It is not logical for them to subsidise water tanks. It would have been if the decision to upgrade had not gone ahead.
 
That said I certainly don't want to discourage people from installing water tanks. At the very least a small 5000 litre tank like we have, provides some security in the case of a major disruptive event that either damages our water infrastructure, or takes the grid out for an extended period. But people need to understand the costs and benefits before making a decision.
 
Below is some relevant information from the MBIE website re installing water tanks without a permit –
 
Tanks and pools -
 
Building work in connection with a tank or pool and any structure in support of the tank or pool, including any tank or pool that is part of any other building for which a building consent is required, that:
 
(a)does not exceed 500 litres capacity and is supported not more than 4 metres above the supporting ground; or
(b)does not exceed 1,000 litres capacity and is supported not more than 3 metres above the supporting ground; or
(c)does not exceed 2,000 litres capacity and is supported not more than 2 metres above the supporting ground; or
(d)does not exceed 4,000 litres capacity and is supported not more than 1 metre above the supporting ground; or
(e)does not exceed 8,000 litres capacity and is supported not more than 0.5 metres above the supporting ground; or
(f)does not exceed 16,000 litres capacity and is supported not more than 0.25 metres above the supporting ground; or
(g)does not exceed 35,000 litres capacity and is supported directly by ground.
 
A building consent is not required for the construction of any tank or pool or its structural support. This is as long as various requirements are met relating to its capacity and height above the ground, as listed in subclauses (a) to (g) of exemption 23.
 
Budyong Hill – Chair Renwick Water Group. 
​Posted January 2020