christopherkev if Greg is correct about you playing GT5, perhaps I (and/or others) can help you further in the GT5u thread. Providing screenshots may make it easier for you to explain the setup you're attempting. In the meantime, since you mention a "tank", I wonder if you're using a tank from another mod, such as BuildCraft. GT5 pump covers won't interact with BuildCraft tanks/pipes. The only "tank" blocks in GT5u are the quantum tanks, and I'd be very surprised if you were able to build one of those before figuring out the ore washer.
Thank you Mauve, thank you GregoriusT, I was able to get water in to the Ore Washing Plant. The solution was a railcraft Water Tank and wood fluid pipes.
There was another post, I can't find, who made the suggestion of the wooden fluid pipes. Thank you too.
I'll be going to the GT5 thread as you suggested for future questions with anything else GT5