bowlingo, you're drip-feeding the forum with a load of questions, each related to the other. How about you outline the whole design (and be willing to redesign the thing if necessary) so that we've half a chance of seeing the whole picture, and giving appropriate advice to you.
He has asked numerous questions about this system. It seems he is building an automated hydroponic system. One of the main applications of hydroponic systems is for growing exotic smoking herbs. I'm sure the OP has no intention of cultivating such a crop and this system is intended for his tomatoes.
If the OP thinks his posts and purchases haven't registered on Mr. Plod's radar, I'd suspect he may be in for a rude awakening.