Northern Ireland's water supply is facing a "network failure" as the hot weather continues.
On Saturday NI Water poured 705m litres of water into its distribution system - 120m litres more than normal.
Last week it warned that a hosepipe ban could be on the way.
Household consumption is up by more than 15% during lockdown, and with little recent rainfall reservoir water levels are dropping.
At Spelga Dam it is down by more than 3m.
NI Water is calling for urgent action from everyone to reduce their water usage.
It said that due to the hot weather and more people at home because of the pandemic, demand is outstripping supply.
Des Nevin of NI Water said: "If demand continues at this level it will lead to failures in our network and customers in certain areas will lose supply or suffer low pressure.
"Some customers over the past few days are already experiencing this, especially those on high ground.
"We are asking our customers to help us, especially over the next few days where the temperature will continue to be above 20 degrees.
"We know from the increase in our night usage some customers are leaving sprinklers and hoses on overnight: please stop. A hose uses more water in one hour than the average family uses in a whole day.
"While it is tempting, don't fill swimming or paddling pools. This is a waste of a precious resource. Filling a 12ft swimming pool in your back yard uses the water for 500 people's daily handwashing.
"A pressure washer can also be a massive drain, so please think about whether the task is really essential at the moment.
"We want everyone to enjoy their home and garden, we just need people to think about how they use their water and if what they are doing is essential." NI Water asks the public to:
- Stop using garden hose pipes and sprinklers, and use a watering can instead. A sprinkler can use as much as 1,000 litres of clean drinking water in a single hour, more than a family of four would use in a whole day.
- Don't fill swimming/paddling pools and hot tubs.
- Buy water-efficient plants when visiting garden centres.
- Use mulches like bark chips or gravel to retain moisture and keep weeds down.
- Turn off the tap when brushing your teeth, as a running tap can use 6 litres of water per minute.
- Load up your washing machine, as half-load programmes use proportionately more water.
- Take a shower instead of a bath. A bath can use up to 100 litres of water, but an efficient shower uses under 50 litres, and
- Avoid washing cars and vans often, and use a bucket and sponge, not a hose, when you do.