It is likely to be a small problem with the seals at the bottom of the solenoid as mentioned. I would do this , First turn off the CO2 at teh tank, pull the quik connect electrical connections off and then turn the solenoid counterclockwise to remove it. Make sure the seals (o-rings?) are in place but take some preventative action to make them seal better and last longer. Lube is an often missed item in our equipment but it does that same as for a car. It makes things last!
One of the easy items that I use often for the fish room is plain simple, no scent no flavor petroleum jelly. It is no longer petroleum and waterproof to a good extent, so just wipe on a smear or sheen of jelly before putting it back together and there is a good chance it will seal again. If it doesn't due to the rings being mashed, try turning them over or rub them to try to return them to the normal shape.
If no luck there, it may be new is needed but getting exactly the right size of O-ring is a pretty good trick, so I try to make them last! The hardware may have the right one but it's a trick!
Last edited by PlantedRich; 08-05-2020 at 01:25 PM.