I just moved into a house and I've been struggling to get the bathtub plumbing working 100%. When I originally moved in, the tub wasn't getting any hot water at all. I attributed it to the water quality (private well w/ high levels of hardness, iron, manganese), so I took out the shower control cartridge, turned the water on and let the water blast freely from the pipes. Some gunk game out and ever since then I get hot water, however it's pretty inconsistent and it doesn't seem to last long. Now, when I first turn on the hot, it comes out very hot initially, but almost immediately it gets cooler and over the course of a 7 minute shower I have to keep turning the hot up until eventually it's up all the way and the water temp is only lukewarm.

There doesn't seem to be a problem with other faucets, they get very hot water. Last week I had a whole-house water filter installed to tackle the water quality, but I'm still having this issue in the shower. I even bought a new shower control cartridge and installed it this weekend, but no improvement.

Water heating is attached to my oil furnace.

I'm pretty stumped at this point and dreading expensive repairs.

thoughts... first, if you have galvanized iron pipe plumbing, start replacing it. particularly with hot water, they gunk up with salts... often by this time, only the caking is holding the water in, the rust will have started to pinhole the pipe.

second, there are many complaints on this board of combination furnace/heater units being wildly inconsistent and inadequate at providing hot water. get a separate water heater. seems to me the combo only works when you need heat all the time.

I'll have to look at other threads about combo furnaces. I was hoping to avoid something like buying a whole new system, since I just spent $2k on the water filter/softener, but if that's what it comes down to, I'll just have to bite the bullet.

Still, I can't help but worry that something else is at play.

there could be controls issues, but you will find other cases in this plumbing thread. my read of seeing them periodically as seasons change is that this is like a Winnebago formula racer... you may be able to sleep 6, but that does come in handy as you have to have 6 shifts of drivers and 48 hours to finish the first leg.

I too think the problem lies in the boiler itself. But trouble shooting via the web is sketchy at best.