UPDATE 2pm: TWEED water restrictions are set to continue as council works to flush salt water out of Bray Park Weir.

Council has released water from Clarrie Hall Dam to flush salt water out of Bray Park Weir after high tides overtopped the weir wall on Monday night.

Council's water and wastewater manager Anthony Burnham said the flush of water from the dam should reach the weir by 5pm today.

"This morning's release from the dam also should be sufficient to hold back any salt water from tonight's high tide, which is expected to be 200mm above predictions," Mr Burnham said.

More water tests will be conducted about 10pm tonight and if the release has sufficiently reduced the salt content in the weir, water restrictions will be lifted tomorrow morning once the reticulated water supply is switched back on.

Council confirmed that if the release from the dam does not sufficiently flush the weir pool, a second release will occur tomorrow morning, meaning restrictions will remain in place longer.

Council also has drained the salt-charged water from the Bray Park Water Treatment Plant and water mains. It has not drained the affected Hospital Hill reservoir in Murwillumbah as any residual salty water will dilute once fresh water enters the system.

Mr Burnham said the tidal predictions for Bray Park were inaccurate, with tidal data recorded at the entrance to the Tweed River confirming that since Saturday actual tides have been up to 380mm higher than the predicted tides.

"Council uses tide prediction information available through the Bureau of Meteorology to manage the risk of the weir wall being overtopped by salty water," Mr Burnham said.

"Plus, the natural flow of the Tweed River also helps to hold back a king tide.

"Last night's incident occurred because the predicted tides, together with the fact that the natural water flow from the Tweed River was still going downstream over the weir wall, informed Council's decision that sandbagging to raise the height of the weir wall was not warranted.

"In the past, we have had no issues with tides of 1.87m but, this time, the downstream river flows were not strong enough to hold back the salt water."

The predicted tides at Bray Park were to be 1.79m on Monday night and 1.81m on Tuesday morning respectively. The actual tides were 2.17m (Monday pm) and 2.11m (Tuesday am).

Council has advised the North Coast Public Health Unit of the situation.

People with medical conditions, such as those using dialysis, are advised to contact their usual medical provider for advice.

EARLIER: IMMEDIATE outdoor water restrictions have been put in place across the Tweed Shire as a precaution due to salt water getting into Bray Park Weir overnight.

While the restrictions are precautionary only, residents are being urged to not use any water for outdoor purposes, including gardening and washing cars.

At this stage, indoor water use and commercial operations are not restricted.

Council's water and wastewater manager Anthony Burnham said tests done this morning by council's Tweed Water Laboratory confined total dissolved solids of 620mg/litre at the weir.

"We know that Murwillumbah water is most affected but ask all shire residents to restrict water use at this stage," Mr Burnham said.

"Alarms at the Bray Park Water Treatment Plant alerted us to the issue about 8am (today). While we will investigate the cause further, at this stage I understand the salt water ingress resulted from a higher than predicted tide. Council's normal operating procedures are to place sandbags on the weir wall to raise the height of the wall in these events.

"As well, the natural flow of the Tweed River normally works against the tide to keep salt water out of the weir but current river flows are low."

The restrictions are likely to be in force for 24 hours to two days as council works to rid the weir of the salty water.

Residents are advised not to drink their tap water if it tastes salty but instead use bottled water.

Council will provide an update on the situation about noon today.

The drinking water for Uki and Tyalgum is not affected.