We have a freshwater bore and I recently replaced the very old pump with a 1hp Pentax pump and Trevoli 18 litre pressure tank system. For reasons I won't go into, the pressure tank has lost its precharge (nominally 2bar/30psi), and I want to recharge it. The system runs as it is, but due to micro-leaks in the system, the pump runs for 6sec or so every minute.
I want to recharge the tank to minimize the pump cycling, and I'm worried that the diaphragm in the tank is being stressed somehow without the tank air pressure to contain it as the water enters the tank.
I have a digital pressure gauge and the tank has a standard bike/car tire valve fitting on top, so I'm assuming this will be OK to check the pressure. The pressure gauge indicates sensible values on the car's tires.
I have a couple of problems:
I have tried putting air in with a cheap cigarette lighter adapter 12v air pump, but the pressure gauge fitted to the air pump shows the pressure ramping up very quickly towards the 150 psi tank maximum (I always turn the electric pump off way before it gets there !). In fact, it's almost as if no air is getting into the tank. Pressing down on the center bit of the valve doesn't result in the usual "pffft" and the hand-held pressure gauge doesn't show any pressure - it's almost as if the air pump is trying to pump into a dead-end. My assumption is that the valve on the tank should open and let the burst of air from the pump into the tank. The air fitting on the end of the pump has a lever-operated clamp instead of a threaded attachment: and I'm wondering if this isn't allowing the valve to open (the fitting completely covers the shank of the air valve - the air fitting has a center protuberance which is supposed to depress the corresponding centre bit in the valve and I don't think the fitting can get far enough over the valve in order for this to happen and open the valve). Any comments?
Instructions I have read say I should 1) turn off the pump. 2) open a faucet and wait for the water to stop flowing. 3) Put air in to 2 bar / 30 psi. 4) Close the faucet. 5) turn on the pump. Should I expect the pressure tank to be empty of water after step 2 (it doesn't seem to be)?
I had some success with the following:
- turned the power off to the pump
- undid the hose from the pressure tank outlet and let the pressure tank empty out.
- tried various methods to get air into the tank, none of which seemed to be doing anything. I couldn't get an air pressure reading off the tank.
- connected up the hose to the outlet.
- switched on the pump.
Remarkably, it is behaving much more like I would expect it should. Before (this is with no taps open), it was running for a few seconds every minute, now it runs for 20-30 secs every 30 mins or so, and the tank now holds an appreciable charge, i.e. it supplies water for a good length of time before the pump starts again.