We have three 1.6 gal briggs toilets in a two storey home all of which leak, evaporate or drain down to a unusable amount of water over a couple of days without any prior usage. We are located in a high wind area but the water seems to go no matter if the wind is blowing or not. Any solutions? Could it be a negative pressure situation? or excessive evaporation? or imroper venting? If its the wind is there any device to put on the vent stack to minimize its affect on ourn toilets?