I have a hot water radiator heating system. Recently a pipe burst and the plumbers had to drain the entire system. My boiler is in the basement and there are 3 floors above it. They had to fill the boiler to 25 psi of water in order to get water all the way up when bleeding the top floor radiators. When done they drained enough water out to make it 20 psi saying that is a better pressure (about 6-7 psi per floor). now I find the top radiators aren't warm and when I bleed them- air comes out then slows to a stop never getting any water. should I add more water to the system and is it bad to keep 25 psi in the system all the time?