I just find a socket that fits the cup and tap it in - make sure the edge of the hole is quite clean - some folks use sealer on them, but careful to not push any inside to foul the water jacket - also don't just replace one, if one needs it, do them all

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics