This is not something unreasonable for them to have as a concern. For example, city water companies in many instances have their own well, which they test for water quality. (always debatable though, to me) When we were on city water (as opposed to being on our own lovely well, now) we had strong communications from the water company that, being in an agricultural area with livestock water tanks etc which were filled with hoses, to be extremely careful about backwash from hoses in livestock tanks - when the water was turned off at the faucet the hose HAD to already be outside of the water tank, because, the hose would after a few moments of being turned off, reverse the water flow back in the city system. Weird~but there were a couple times when this exact kind of bacterial issue ("bad water") contaminated the city water.
It is not an unreasonable concern. It is unreasonable to state that anyone is required to let you into their home when you have no proof or even suspicion that they are doing anything wrong.
Mass surveillance is illegal.
Unwarranted searches are illegal.
Sobriety checkpoints are illegal.
Entering private property without consent, and without court-granted approval or reasonable suspicion of an emergency is illegal.
I am not saying they are actively or consciously trying to do anything nefarious, but if OP doesn't want random government employees in his home, it is his right to make them first prove cause to be there. If he is worried about his plumbing, he can also just hire a private plumber of his choosing to do an inspection.
This is not something unreasonable for them to have as a concern. For example, city water companies in many instances have their own well, which they test for water quality. (always debatable though, to me) When we were on city water (as opposed to being on our own lovely well, now) we had strong communications from the water company that, being in an agricultural area with livestock water tanks etc which were filled with hoses, to be extremely careful about backwash from hoses in livestock tanks - when the water was turned off at the faucet the hose HAD to already be outside of the water tank, because, the hose would after a few moments of being turned off, reverse the water flow back in the city system. Weird~but there were a couple times when this exact kind of bacterial issue ("bad water") contaminated the city water.
It is not an unreasonable concern. It is unreasonable to state that anyone is required to let you into their home when you have no proof or even suspicion that they are doing anything wrong.
I am not saying they are actively or consciously trying to do anything nefarious, but if OP doesn't want random government employees in his home, it is his right to make them first prove cause to be there. If he is worried about his plumbing, he can also just hire a private plumber of his choosing to do an inspection.