The water coming from my bath tub faucet will only get luke-warm at best. (even for a 22 month old, he says "cold daddy"...). The tub has a Symmons Model A faucet which I believe to be as old as the house, built in 1994. Every other hot water source seems to have plenty of hot water. The downstairs bathroom sink, the washing machine, the kitchen sink, the master bath sink and shower, all piping hot. As a first attempt at a fix I replaced every component for the symmons, so it's pretty much rebuilt. The boiler is a Trianco HeatMaker, I believe also original with the house. In the past two years I have replaced almost every replaceable component on the boiler. Fast fill, draw offs, over pressure relief valve, zone valve control heads, the Honeywell control panel, its all been replaced! I've lived here two years, I'm tired of throwing money at the boiler, so it's on the list of things to replace this summer. The boiler is an all-in-one unit, providing hot water to the baseboards and domestic hot water. The house heats fine, and like I said, all other taps seem to have plenty of hot water.
Is it possible that the pipes to this particular tub are smaller than they should be? Did I miss another component in the symmons model A that could be the culprit? (I replaced the two seats, the main spindle and the diverter spindle, along with the necessary washers, etc.
What's my next step? What else can I investigate? How can I further trouble shoot?
Please see the video of my tub and boiler below: