Plumbing question

I renovated my bathroom and added a large bathtub, and now the hot water runs out about halfway into filling it up. I have a 40 gallon hot water heater…could that possibly be too small? Would a tankless heater make more sense (not that I’m dying to spend more money!)

Thanks in advance!

deborahg said:

I renovated my bathroom and added a large bathtub, and now the hot water runs out about halfway into filling it up. I have a 40 gallon hot water heater…could that possibly be too small? Would a tankless heater make more sense (not that I’m dying to spend more money!)

Thanks in advance!

What’s probably happening is as you’re draining hot water from the tank to fill the tub, the tank is being refilled with cold water. It takes a while for that water to get heated up. A tankless heater would potentially solve that problem but it’s got to be the right BTU rating for your house. 

Maybe you just need to set the thermostat a little higher on the hot water heater. But be careful not to go too high so you don’t risk scalding yourself - you might want to post a pic of your water heater thermostat and let a bunch of us look and go “hmmm” while rubbing our chins for a little while. Anyway, then your mix of hot to cold water for the tub would be less hot water and you wouldn’t run out as quickly. 

deborahg said:

I renovated my bathroom and added a large bathtub

Do you know what the volume of your bathtub is?

That will go a long way towards giving you the answer.     

The new deep free standing tubs hold twice as much water as your water heater. That’s one issue, the other issue is the thermostat on your water heater is at a low setting. If setting is at ‘A’ it’s not going to fill the tub with enough hot water. 

Also, it's winter, and the cold water has gotten colder than in the summer. 

I thought my hot water heater was having an issue heating water because I started turning on a much higher proportion of hot than usual for my showers. But it ended up that since the cold water has gotten quite cold, and the room is also colder, I just need more hot water to get to the warmth I want.

Great info thank you! 

I checked and it’s a 40 gallon hot water heater. Here is thermostat! 

Hmmmm

Since you have a gas pilot light, I would guess that your hot water heater is at least nine or 10 years old.

You do obviously have some room to increase the temperature of the hot water. You may want to see if you can get a thermometer and test how hot the water is that comes out of your tap. It should be about 120°, which is considered safe but hot enough to kill bacteria. Going much higher than that, as is indicated right there on the water heater itself, increases the risk of scalding.

If it was me, I would probably turn up the thermostat a little bit and see if that helped the problem. Obviously replacing the water heater with a larger capacity or tankless water heater would best solve the problem. But as you pointed out, that runs into a bit of money.
I don’t know what experience anyone has had with a tankless water heater. I thought about it, although our current water heater seems to be working fine.

Turn it up to ‘C’…

All water heaters have a pilot light, this one is fairly new because it has the electronic ignition. The pilot light is inside the case, sealed up. 
when was the last time it was drained to remove sediment? 
Whenever you have to change it just replace it with a 50 gallon. 
Make sure you’re not running the dishwasher or laundry when you want to fill the tub. 

mrincredible said:

I don’t know what experience anyone has had with a tankless water heater. 

I've been running a similar system for some years now.  It is adequate for my needs - but I don't have a bath in this house - so it only needs to supply hot water for my shower, the washing machine, and dish-washing.  The water feed to the unit is via a solar heater on my roof.  I don't have snow or freezing weather in my part of the world, so that option may not work for you.

Jaytee said:

Turn it up to ‘C’…

All water heaters have a pilot light, this one is fairly new because it has the electronic ignition. The pilot light is inside the case, sealed up. 
when was the last time it was drained to remove sediment? 
Whenever you have to change it just replace it with a 50 gallon. 
Make sure you’re not running the dishwasher or laundry when you want to fill the tub. 

From what I can see it has an old style pilot light. It has a setting to manually restart the pilot light when it goes out. This kind of pilot light stays on all the time which isn’t energy efficient.  Our water heater is about ten years old and has the same configuration.

Newer water heaters often have an electronic spark ignition like a gas stove. So there’s no need to relight anything if it goes out. 

mrincredible said:

From what I can see it has an old style pilot light. It has a setting to manually restart the pilot light when it goes out. This kind of pilot light stays on all the time which isn’t energy efficient.  Our water heater is about ten years old and has the same configuration.

Newer water heaters often have an electronic spark ignition like a gas stove. So there’s no need to relight anything if it goes out. 

this has the electronic spark to light the pilot. I’m curious… how and when does your water heater ignite the gas to heat the water? When you turn on the hot water tap? 
The tankless water heaters don’t have a pilot light. That’s a pretty good energy efficient heater if you don’t have a pilot light. What brand is your heater?

Old-school (like mine) - a constantly burning pilot light. The main gas starts flowing and the heater fires up when the water inside gets down to a certain temperature. 

New-school - an electronic ignition that automatically lights the gas when the water inside gets down to a certain temperature. 

I’m pretty sure the one in the picture is old-school. It has a pilot light that remains lit all the time. The “pilot” setting on the knob allows you to relight it in case it gets blown out by a draft, or if the gas gets turned off for service. 

mrincredible said:

Old-school (like mine) - a constantly burning pilot light. The main gas starts flowing and the heater fires up when the water inside gets down to a certain temperature. 

New-school - an electronic ignition that automatically lights the gas when the water inside gets down to a certain temperature. 

I’m pretty sure the one in the picture is old-school. It has a pilot light that remains lit all the time. The “pilot” setting on the knob allows you to relight it in case it gets blown out by a draft, or if the gas gets turned off for service. 

I just installed a water heater last year and it was a standing pilot on. Brand new Rheem. They are still selling them with the pilot on. So it’s not so old school. I don’t think you would save that much on gas eliminating the standing pilot. Another issue is , if you lose electricity you automatically will run out of hot water, because obviously you would need a live line to heat up the probe that would ignite the gas? 
Personally I prefer the manual electronic igniter, because it’s completely sealed up and drafts don’t affect it. The only thing that would put the pilot out would be a flooded basement or you lose the gas supply coming in to the house. 
It’s interesting that they’re trying to make heaters more efficient but I don’t think the savings are that great, pilot lights use minimal amounts of gas. I installed an electric water heater in a rental property about 22 years ago and it’s still working fine.