They are and they are quite large. One water tank in the V-birth and one in the quarter birth. Also a smaller one on the holding tank in the V-birth. The two water tanks have clean outs. At one time I wanted a sensor in the holding tank and got one of those that are foil in a pvc pipe. It was mounted in a male pvc pipe thread fitting so I drilled a hole in my tank top and taped it with a one inch pipe tap. The mounting worked perfectly, the sender not so well. PVC is easy to work with.