Water pressure loss every 30 seconds
Something is not right with your pressure tank/pressure switch.

The most likely (there are several less likely options) is that you may have a failed bladder, assuming the usual modern case of having a bladder type tank (where a membrane or bladder is supposed to prevent contact between the air in the pressure tank and the water in the pressure tank.)

Typically the most cost effective way to solve that is a new pressure tank.

But.

There are small odds that things are just horribly mal-adjusted. A properly installed well-pump system will have a pressure gauge you can see somewhere near the pressure tank - you should abserve that while water is running, and pay attention to where the pressure is when it switches the pump on and off. 

You can check by turning off the pump and draining the water; then check the air pressure on the tank (there should be a tire valve, usually on/near the top, sometimes under a cover - use a tire gauge to read that pressure.) If it's zero ( with the water side drained &amp; at zero), you almost certainly have a failed bladder, but try pumping it up (with a tire pump - there should be air in there) if it does not hold pressure, you definitely have a failed bladder. If it will hold pressure, it should be adjusted to about 2-3 PSI below where the pump turns on (so if the pump starts at 40 PSI, 37-38 PSI) 

Depending what type of pump you have, restarting the pump may be more or less difficult - if it's in the well (submersible) it's generally no work at all - if it's a pump in the house you may need to prime it, and thus you might not even want to start the "turn things off and drain the system" checks until you have an understanding of how to prime and restart the pump, or you won't have ANY water until you do.

To help you understand the (most likely) problem, the pressure tank acts to store water under pressure by compressing an air bubble. The tank and resulting air bubble are typically supposed to be sized to allow for 1 or 2 minutes of pump operation (which results in a certain volume of water) each time the system cycles. If the air bubble is not the right size, much less water is stored, and the pump cycles more frequently. In the "properly adjusted" state, the 2-3 PSI below the pump turn-on (also known as cut-in) pressure prevents any noticeable loss of pressure (the tank is still supplying water as the pump starts to replenish it), and the pressure simply varies between 40 &amp; 60 PSI, or 30 &amp; 50, or 20 &amp; 40, or possibly other values.

A "much rarer these days" case would be a non-bladder type pressure tank - those have contact between the air and water, and the air gradually dissolves into the water, so it needs to be replenished. Those systems typically have valves that are supposed to suck in air as the water is pumped, but they may malfunction, and the typical solution until they are fixed (or the whole thing is replaced with a bladder tank) is to pump air into the tank manually if a valve is provided for that, or to drain all the water out of the tank, which provides a tank-full of air when you restart the pump.