I have a funny situation in the town I just moved to. Instead of having 3/4" or 1" pipe bringing water into my house I have 5/8" pipe bringing in water. Because of this, when I run the shower (or some other item) there is not enough water pressure to run other taps, etc. There is the regular pressure coming in on the pipe, its just a smaller size and so volume is down. I am updateing my plumbing and want to find a way to fix this issue (short of digging up my yard and foundation and running a new water line to the main). I have had two ideas but have no idea if one is better than the other or if they would even fix the issue.

Idea 1:
Install an 80 gallon pressure tank after the water meter. If I did this would the municiple water pressure be enough to fill the tank or would a pump still be required.

Idea 2:
Install a jet pump on the line after the water meter. Would this work to increase the pressure or would there not be enough water volume and overwork the pump.

Any thoughs would be great. Thanks.

Pressure tank should help.

Pump with pressure tank will help a lot.

I installed a grundfos on demand pump(my water service is lead, and I didn't want to dig up either) The on demand pump doesn't require a pressure tank, there is a very small one built right into the pump. I have found that it gives me great pressure when only using one faucet, but still lose pressure when using more than one faucet, because no matter how hard my on demand pump tries, there is just not enough volume. I haven't added a large pressure tank to my system yet, but I believe this would take care of my problem( to a certain extent). I would try a jet pump with pressure tank. But you know as well as I , that the best sollution would be to replace water service. Hope the pump and tank works, please let me know how it turns out.

Let's not confuse lack of "pressure" with lack of "volume".

You have undersized pipes. Yes, you certainly can increase pressure to increase water volume delivery but you have to be ready to accept compromise. Higher pressure in small diameter pipes are noisy and puts too much stress on fittings, valves and washers.

You are mentioning you want to update your plumbing. What exactly do you plan to do ?

I will be changing all my existing copper pipe (which was put in in 1960) to PEX. I'm not convinced that a pump will be the answer. If I have decreased water volume will that not make the pump work harder than it needs to?

The pressure coming into my house is fine, it is just a volume issue. If I install an 81 gallon bladder pressure tank will this work? I guess my question is will the water pressure from the town be enough to fill the tank or is a pump required to fill the tank. I would think that town water would be enough.
Any further thoughts would be great. Thanks.

The answer to your question is yes and no. Yes, your volume problem would be solved to some degree. You are basically using the tank as a water resorvoir. The no comes in that, once you have worked through the twenty or thirty gallons (or whatever it will be) of reserve, then you will be back to where you are now. At least that is how it would look to me.

The tank would have a maximum pressure of whatever the city pressure is.