This goes for all mod packs including openblocks:

Just wanted to point out that XP Shower should be kept off since every xp orb that drops is counted as an entity and can lag the server if few of them were kept on all the time.. if you are using it to convert liquid xp to mob essence (using mfr sewer) just do so in a responsible manner.

Pro tip - u can just right click (with an open hand) an openblocks tank, with liquid XP inside, to drink some of it and restore lvl-s.. no need for shower