Hi Tony, I am assuming that you are only using a soluble water based solution in the sprayer such as Tomorite or a degreaser such as TFR? If so, then there are normally only two reasons that the relief valve operates and that is 1) that you have over-pumped the unit causing the valve to actuate the pressure relief valve or 2) that it has been over-filled. If it had been working correctly before it started failing, unscrew the end of the nozzle and make sure that nothing has blocked the outlet as this could cause back-pressure and similar issues. If none of these work, then the final resort would be to return the item to the seller if you have only recently purchased the item.