It's a blessing for the donation of requisites. At our Wat we take refuges and precepts, do some chants, then the lay people chant an offering chant (in our case there is some Thai as well, but this is the key Pali part:
P 150 http://www.accesstoinsight.org/lib/auth ... anting.pdf
Imani mayaa bhante, bhattani, saparivarani,
bhikkhu-saoghassa, onjay›ma. Sadhu no bhante,
bhikkhu-saogho, imani, bhattani, saparivarani,
pattigganhatu, amhakam, dıgha-rattam, hitaya,
We present these [those] foods of ours, together with
their accompanying articles, to the Bhikkhu Saogha.
May the Bhikkhu Saogha accept these foods of ours,
together with their accompanying articles, for our
long-term welfare & happiness.
The monks reply with this chant, which is when we pour the water.
P 170 http://www.accesstoinsight.org/lib/auth ... anting.pdf
Evam-eva ito dinnaa
Icchitaa patthitaa tumhaa
Sabbe purentu sankappa,
Cando pannaraso yatha
Mani jotiraso yatha.
Just as rivers full of water
fill the ocean full,
Even so does that here given
benefit the dead [the hungry ghosts].
May whatever you wish or want quickly come to be,
May all your aspirations be fulfilled,
as the moon on the fifteenth [full moon] day,
or as a radiant, bright gem.