What Size Water Heater Do I Need for A Walk In Tub?

Patricia Oelze
by Patricia Oelze

You finally get into your new walk-in tub to have a nice hot bath and after it is about halfway full, the hot water is gone. Has this happened to you? If your hot water heater is too small, you are not going to be able to have that hot bath for a while.

Most tubs require a water heater that’s at least 50 gallons. If your tank is not large enough, you’ll run out of hot water too quickly. With the standard tub being 30″x60″, a 60-gallon water heater or larger is required for ample capacity. Another option is to add a supplemental unit near your current heater.

Whether you got that walk-in tub for therapeutic reasons or for safety reasons, it really does not matter if you cannot fill it up with warm enough water. The best time to think about how much water you need is not after you buy the tub because they can be a pretty big investment.

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What to Ask Before You Buy

There are many important questions that you need to ask about the tub before you agree to purchase it. The number one question is how much water it holds. If your water heater has to be two-thirds the size of your 75-gallon tub, you will need at least a 50-gallon water heater.

You certainly do not want to spend all your money on a new tub just to find out you need a new water heater that you now cannot afford. Make sure you can fill it before you buy it. And if the one you want requires a larger water heater, wait until you have enough money to get both.

Make Sure You Know the Size

Although the size of walk-in tubs varies, they are typically about three or four feet high, approximately 30 inches wide, and 60 inches long. It is made so that it fits into the size of a regular bathtub but taller so that you have a door to open and step into.

Type of Walk-In TubDimensions (W x L x H)Water Capacity
Rectangular Tub32” x 38” x 36”40 gallons
Standard Tub30” x 52” x 38”50 gallons
Long Tub30” x 60” x 38”70 gallons
Deep Tub30” x 52” x 46”80 gallons
Extra-Long Tub36” x 60” x 38”90 gallons
Two-Person Tub36” x 80” x 38”120 gallons

Get the Best Door for Your Needs

Most walk-in tubs have a door that opens inward, but some do open out, which is good for those who have major mobility issues. That is because they are easier to get into and out of. However, doors that swing out need more space.

Another type of door is the rising wall walk-in tub that is about 24 inches off the ground with a side panel that moves up and down. You can get into these from a seated position, making it great for those in a wheelchair.

Fast Filling or Freezing

One of the disadvantages of a walk-in tub is that you have to sit in there and wait for it to fill up. That is because it has a door. You cannot open the door while it is filling, of course. It can get mighty chilly in there while you are waiting for the tub to fill. Even more so if the water heater is not large enough to fill the tub.

It typically takes about five gallons per minute for the average bathtub to fill. That means it will take 15 minutes to fill up that 75-gallon tub. That is a long time to sit in the cold tub waiting for it to fill. Ask about getting a fast-filling system that has more outlets.

How About a Step-Up Tub?

An alternative type of tub is the therapeutic step-up tub that has two steps to get into it. Similar to a jacuzzi tub, you just walk up into it and sit down. There is no need to step over the side of the tub or open a door. However, you have to be able to go up at least two steps.

A step-up tub also uses up a lot of hot water. No surprise there. You will probably need at least 60 gallons for that kind of tub to fill. But at least you will not have to sit in the empty tub while it fills. You can stay nice and cozy and wait for it to fill before you get undressed. But these are not as safe for those with mobility issues.

What About Everyone Else?

If you do not live alone, you have to also consider those who live with you. What if someone else needs to use the hot water? They may need to wait up to an hour to use it after you fill up your tub. Hopefully, nobody will want to take a shower during that time.

It is probably best to get a water heater that can fill your tub and have some left over. Just for those who want to wash their hands or do the dishes while you are in there. Add on another 10 gallons to the size of the tank you are going to need if you live with other people.

The Cost of a Water Heater

Depending on the size that you need, you may be spending quite a bit on a new water heater. But it would not make much sense to get a nice new walk-in tub if you cannot use it. Unless you enjoy ice-cold baths.

Tank SizeAverage Price
40 Gallons$335 to $1,650
50 Gallons$405 to $2,250
75 Gallons$905 to $3,050
80 Gallons$1,000 to $3,500

Gas or Electric Water Heater

If you have both gas and electricity in your home, you have to decide whether you want a gas or electric water heater. They both have their pros and cons. Although gas water heaters are usually more expensive to buy, they are cheaper to run. Here are the specs:

Longevity8 to 12 years8 to 12 years
Reheat Rate30 to 50 minutes1 to 2 hours
Energy Efficiency60% to 70%95%
Lifetime Cost of Use$5,000$6,250
Cost of Unit$300 to $3,000$200 to $2,800

Of course, these prices vary depending on where you live, the company you choose, and when you are reading this article. These are estimates for 2020. Future prices will likely be more. However, you can always get things cheaper if you wait for a sale. And installing it yourself will save you a bundle.

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Tankless Water Heater

Another option is the tankless water heater, but they are much more expensive. In fact, they can be two or three times more than a regular water heater. The average tankless water heater costs about $3,000 including installation. They are more difficult to install and require more in labor costs.

However, they are smaller and can save you up to 25% on your utility bill and there is a limitless amount of hot water. Endless. That means you can fill your tub, the kids’ tub, and your husband’s tub and still have plenty of hot water for the other kids to wash dishes and do laundry.

So, if the cost is not an issue for you, the tankless water heater may be a good option for you. They also have a longer lifespan, lasting more than 20 years on average. Either way, just make sure you have enough water for that walk-in tub before you buy it.

Patricia Oelze
Patricia Oelze

I am a DIYer who loves writing about anything home-related. When I am not writing, you can find me studying for my PhD in Psychology, photographing nature, and swimming at the lake with my grandkids.

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