In some regions, roof-collected rainwater supplies for household or community use are very common. These systems are very vulnerable to contamination by volcanic ashfall because of the high ratio between the collection area and the volume of the tank. Tank water contaminated by ash is unlikely to be a health hazard as elements released from the ash (particularly iron, manganese and aluminium) can impart an unpleasant metallic taste to the water making it unpalatable to drink, with this effect outweighing the release of any toxic elements such as fluorine from the ash.
For households that use roof-collected rainwater tanks for their water supply:
- If you have ash on your roof and you did disconnect your downpipe from your rainwater tank, wait until rain washes ash from roof, or you clear the ash from your roof, before reconnecting downpipe to your tank.
- If you have ash on your roof and you did not disconnect your downpipe from your rainwater tank, disconnect the downpipe now to protect your tank water. Wait until rain washes ash from roof, or you clear the ash from your roof, before reconnecting the downpipe to your tank.
- If there is ash in your rainwater tank, use your emergency water for drinking and preparing food until official advice is provided, based on the results of volcanic ash analysis and/or water testing.
- You can continue to use your tank water as usual for all uses other than drinking and preparing food.
- In most cases, small amounts of ash (a few mm) are unlikely to make water unsafe to drink but may give the water an unpleasant metallic or sour taste. Over time, fresh rainfall will dilute the chemicals from the ash and improve water quality.
- If your water system uses pumping, check that the tank outlet is well above the ash settled in the bottom of the tank so that ash does not get drawn into pumping equipment where it may cause damage.