The tap water pipe is connected with a self-priming pump. When the self-priming pump is not working, will tap water flow underground through the self-priming pump?

Help you analyze your problem. The structure of self-priming pump is that a one-way valve is installed at the entrance. When the check valve is normal, tap water will not be poured into the well. If the one-way valve of the self-priming pump is abnormal, it may flow back, but it is also abnormal to need another one-way valve. I will talk about this one-way valve later. On average, you use more than 13 tons a day, which is likely to be countercurrent or self-priming pump to pump water into the water pipe. I don't know exactly how you installed it. Under normal circumstances, the self-priming pump cannot be directly connected with the tap water, so the pump will work when the tap water pressure is low, and the water pumped by the pump may also be poured back into the tap water pipe. The current water meter counts normally no matter which port it enters. In other words, if there is no problem with the one-way valve of the self-priming pump, due to your structural reasons, the self-priming pump may also cause problems with the water meter. So I understand that the key point of the problem lies in the connection point between the self-priming pump and tap water, and the connection point must be equipped with a master valve (this is the one-way valve I mentioned earlier, and I will tell you later). The direction is that tap water can pass, but water from self-priming pump can't. If you have this one-way device, you can be sure that it has failed. I hope my analysis can help you.