need help understanding drain and restart procedure.

[tglenn]

I noticed my pressure guage on my Jacuzzi jet pump appears to be stuck so
I'm going to replace it.
While the system is drained I also will repair a dripping frost free sillcock, check the pre-charge pressure and install a shut of (where the red line is ) so I don't always have to drain the entire house. Is this a good idea and location?
I believe all I have to do to start on the work is close the main valve from my cistern and open that faucet pictured below the blue tank?
I think the pump should retain a little water and self-prime? I'm a little scared because 35 years ago when the house was new I ran the system out of water and had a heck of a time getting it to prime. Found out I had sand in the pressure switch and pump. All that was fixed and I never ran it out again but wanted to make sure it will prime itself? Everything is so old I don't want to even have to take out the priming plug on top.
Also in the close up picture. what is the small valve with the red lever and the hose and will I have to use it??

So to restart the system, I'm assuming all I have to do is make sure all of the faucets are closed, or does one have to be on? and then open the main water supply from the cistern. and hold the little lever on the pressure switch until it will stay by itself?
I know this is all pretty straightforward and I usually just jump right into things like that But the previous experience scared me a little bit. Thank you all so much. Sure, Miss Terry.

 

[Valveman]

Yes, you can put a ball valve where the red line is. The pump will probably stay primed. But if not you can fill it from the same hole you took the gauge out of and not have to remove the 1" plug. Can't see it, but guessing the little line from the red handled valve goes to the pressure switch on the side of the motor. Check the air charge in the tank while the pump is off and the water is drained. With the switch working at 30/50 you need 25-28 PSI air in the tank.

 

[Sponsor]

 

[tglenn]

Yes, you can put a ball valve where the red line is. The pump will probably stay primed. But if not you can fill it from the same hole you took the gauge out of and not have to remove the 1" plug. Can't see it, but guessing the little line from the red handled valve goes to the pressure switch on the side of the motor. Check the air charge in the tank while the pump is off and the water is drained. With the switch working at 30/50 you need 25-28 PSI air in the tank.

Thanks a lot, very helpful. And just to be sure when I go to restart everything I want all of the faucets off? Or does one need to be on?

 

[Valveman]

It will prime easier with a few faucets open.

 

[Reach4]

With a jet pump, it takes some time to get the water moving. The pressure tank supplies the water when the pump first starts. It is common to set the air precharge in the pressure tank to 5 psi lower than the cut-in pressure with a jet pump. Air precharge is measured and set with the water pressure zero.

 

[tglenn]

With a jet pump, it takes some time to get the water moving. The pressure tank supplies the water when the pump first starts. It is common to set the air precharge in the pressure tank to 5 psi lower than the cut-in pressure with a jet pump. Air precharge is measured and set with the water pressure zero.

When I depressurize the system is it okay to just use The valve located right below the pressure tank in the picture?

 

[John Gayewski]

You could also use some nipples and what not to put a valve in before the pressure gauge. That way if/when the new gauge goes bad you can just shut off the gauge and replace it easily.

 

[Reach4]

When I depressurize the system is it okay to just use The valve located right below the pressure tank in the picture?

Yes, but you could also use the kitchen sink. True the water pressure will not go all of the way to zero, but that will be close enough if it goes to zero in the kitchen or bathroom. The thing we are trying to avoid is having the water pressure anywhere close to the air precharge pressure.

If the water pressure is say 50 psi, and the pump is not running, expect the air pressure to be about 50 psi. This is useful to compare the calibration of the water pressure gauge, to the air pressure gauge. It is not useful for measuring the air precharge pressure.