I would test it in a bucket outside of your module. sounds like something is wrong... I built mine a few weeks ago and it tested fine in a bucket.
The world is a tragedy to those who feel, but a comedy to those who think.
Horace Walpole (1717 - 1797)
Nearly all men can stand adversity, but if you want to test a man's character, give him power.
Abraham Lincoln (1809 - 1865)