2017 montana 3921fb

[Medmisten]

Hi all. We purchased our 3921fb a year ago. Since the day we brought her home we cannot get the water in the tub to get hot. All other water gets extremely hot but tub water is luke warm. Any suggestions on how to fix this? Thanks in advance for your help.
Michelle

[Mikendebbie]

We have not had that issue in our unit.
I leave it set to 130*. DW has used the tub much more than me and she says we have not had that issue.

During the winter when the water coming into the RV is colder - the water does not get as hot. I recall a few times DW boiled a pan of water to add to the tub. For my showers - I get the hot going then I have to temper it with some cold.

Are you able to take a shower and get HOT water at the bathroom sinks? We do not generally run hot water at two faucets at the same time. The water heater is big enough to satisfy demand at a single point…not as good for multiple points of demand. This is not a problem for us.

These heaters are supposed to be descaled annually but I have not added the plumbing connections to mine to accomplish that. It’s on the list.

If you have a meat thermometer - check the temps of the water at each faucet and come back here with a report. We are at the S&B with the RV out back and I need to hook up the water and just test everything since we had that 12* weather last month. I had blown out the system with air and kept the furnace running throughout the cold. I will try the same test and report back here.

[jimcol]

Mikendebbie makes a good suggestion with the meat thermometer. Make sure you test it with only the hot turned on. If the temp is close to what the other faucets read you may just have a problem with the mixing valve. That's the part of the tub faucet that combines hot and cold to deliver water at the desired temps to the spout. Sometimes the fix is as easy as new parts in the faucet.

[Mikendebbie]

I went out this morning and hooked up the water to my unit - first time since the 12* freeze in TX in mid-December. To prepare for the freeze I drained the water system and blew the system out with air. Additionally I set the furnace for 53* and let it run and I had a small electric heater in the basement for a day but it actually was too hot so I unplugged it.

Here are the temperatures of the water I recorded at each faucet. I let the hot water run for a minute or so until it was HOT to touch then I collected some in a 3" deep dog water bowl. My Suburban thermostat is set to 129*. I measured the temps with a Weber digital meat thermometer.

City water supply - 59*
Kitchen sink - 116*
Half bath sink - 114*
Main bath sink - 120*
Shower - 113*
Bath tub - 100* with the hot WIDE open
Bath tub - 105* if I turned the handle to about half way to reduce flow demand.

Hope this helps.

[DutchmenSport]

I don't know how your bathtub is configured. Is the spigot a single knob you turn and the farther you turn it the hotter it gets? Or is it 2 separate knobs, one for hot and one for cold?

If yours is a single knob, (like they use in showers), the knob assembly is adjusting and mixing the hot and cold. It may never get truly hot.

In my MHC, I have a shower. Immediately I was horribly agitated because the single knob turn handle never got fully hot. I ended up pulling the knob assembly from the wall and switch the hot and cold lines. Now when it initially turns on, its truly 100% hot water instead of 100% truly cold. Now, the further I turn the knob the colder it gets.

My wife and I are the only 2 using our shower, unless our son and grandson go with us (maybe once a year). Everyone knows the switch I made in the plumbing, so everyone knows how to turn the faucet. Besides, if the faucet is just initially cracked, it always starts out cold and slowly increases in heat as the water sitting in the lines is cold and has to bleed out as it's replaced with the distance it travels from the water heater. And we never take showers back-to-back. We've never been scalded or burned.

So, is yours 2 handles or 1?

I absolutely hate shower mixers. In our house, I've done a LOT of remodeling, replumbing, and rewiring. In both bathrooms, I got rid of the single handle (mixers).... They just suck..... and replaced them with 2 handle faucets. When we want HOT water, we want HOT water!

[Mikendebbie]

The bathtub faucet has two handles (see blurry screen shot below - sorry).

[Foldbak]

And welcome to the forum.

[ScottnSue]

Does your camper have an on demand water heater ? We had one at the church center. We noticed if you ran the water fast it didn't get as hot as if ran a slower rate. Seems it can only heat the water so fast. Just thought, if you run the water in to the tub at a slower rate is the water hotter ?

[Mikendebbie]

If you look at the two bath tub temps I listed in post #4 - that is the difference. The higher temp of 105* was a result of “slowing” the water down as it passes thru the heating coils.

[BobStack]

Welcome to the forum and congratulations on the new rig! Hope to see you out there!

[ingalmi]

We’ve had our unit since 2017 and bought it new, and the short answer is throttle the hot water handle on the tub down and leave the cold water off until you get the desired amount of water in the tub then add cold if necessary. Water flows much quicker thru tub faucet and the hot water heater can’t keep up. Obviously warmer days help.

[MichiganBill]

Just dealt with similar at home. If your bath / shower control is a single handle it likely has an anti-scald feature as well as an adjustment to control the max hot water allowed in. The anti-scald is typically a pressure balance valve within the faucet. The max hot is often a screw adjustment within the faucet.
Turn water off. Pull handle off (some have a set screw at bottom, some you grab the sleeve behind the faucet and unscrew. Likely other attachments I'm not aware of. Once handle is out of the way you will likely see a screw that stops the faucet rotation towards hot. You can adjust that screw to allow more hot water flow.
The balance valve is behind the hot water stop. The hot and the cold will come in on either side of a shuttle valve. Sometimes those valves stick with contamination. See if you can free it to shuttle side to side. If not, many are replaceable.
Good luck.

[Mikendebbie]

All faucets in my unit (2018 3921FB) are two-handle faucets - except the kitchen sink. Anti-scald feature is not an issue. OP was questioning why the water at his bath tub was not as hot as it is from the other faucets in the trailer. More than likely the reason has to do with water flow...bath tub faucet allows a larger flow than the bath sinks and the kitchen. I think the recommendation here is to try throttling back on the hot lever at the bath tub and do not open it wide open - therefore letting the water spend "more time" in the water heater coils - thus warming the water up more.

The water coming out should be hotter, but it will take a little longer to fill the tub. DW always adds a pan full of boiling water just before she gets in. Works every time.

[ILOVEFISHINGEDISTO]

I just posted the same issue on my 2017 3920FB After reading this response I turned on my hot single water faucet wide open, Luke warm, throttled it back to about the 11 o’clock position and steaming hot water. My wife is happy now. Love the forum group.