MANILA (UPDATE) - A bypass valve that splits water from reservoirs between the capital's two concessionaires is open, a regulator said Friday in response to a Facebook post, as he assured government action on a shortage that has affected tens of thousands.

Closing the bypass valve will stop water from Angat Dam from flowing to Manila Water, the east zone concessionaire affected by the shortage, said Metropolitan Waterworks and Sewerage System Chief Regulator Patrick Ty.

"For the record, the bypass is open. It is not closed... If it is closed, Manila Water would not have water at all," he told reporters.

"We hope for the understanding of the public and rest assured we are doing everything we can to alleviate the problem to ensure this will not happen again," he said.

The bypass valve splits the 4,000 million liters per day (mld) from the reservoir between Manila Water and Maynilad Water Services Inc. in a 60-percent-40-percent divide in favor of Maynilad, he said.

Manila Water gets 1,600 mld while Maynilad gets 2,400 mld. The capacity is capped at 4,000 mld due to infrastructure limitations, he said.

If the bypass valve is adjusted to alter the allocation, Maynilad could also be hit with water interruptions, he said.

Maynilad in a statement Friday assured the public that Manila Water is getting its full 1,600 mld allocation from the Angat Dam.

"Maynilad has not done and will not do anything to deprive Manila Water of its 1,600 MLD allocation," it said.

"For its part, Maynilad has been maximizing its 2,400 MLD allocation from Angat Dam to ensure that its customers would have relatively stable supply of water throughout summer, despite a weak El Niño," it added.

Screenshots of a comment on Ty's Facebook post, supposedly from a longtime MWSS employee, has circulated on Facebook. According to the comment, opening the bypass valve will solve the water problem.

"Unfortunately the trolls have started attacking, I had to disengage. I had to assist people... We would rather not engage with trolls," he said.