Kitchen Gas Appliances - Water Heater Low Capacity

I have a John Wood 33.3 gal (151 L) gas water heater (32 kbtu with rated 110 L/hr recovery capacity).

I am finding that the capacity is significantly lower than expected. For example, my upstairs bath tub has approximately 151 L total capacity. I go to fill it up and after it is only 1/3 full, the water coming out is luke warm. However, this doesn't always happen. Sometimes it will have more hot water, but never enough to fill the tub with hot water.

I am planning to do some plumbing upgrades shortly and wonder if the absence of a dip tub would cause low hot water capacity as described.

You need the install a larger heater, go with a 50 gal heater, there the most install size of a heater.

There are several major factors which can cause a tank type water heater to run out of hot water too fast. Among the most common are: Too small a tank.<Undersized for house>

Currently more occupants then there were prior to the installation of the present water heater or former owner of the dwelling. Hot water drawing appliance, etc. is too far from hot water source.

Slow recovery from a prior or previous useage. Spaceout hot water useage 1-2 hours apart to allow for full recovery from cold water to hot water in the water heaters tank.

Colder outside weather means colder water into the tank, which equals a longer recovery time from cold water to hot water, in the water heaters tank. Allow more time for recovery.

Newer tanks are much more energy efficient. The burners BTU inputs are preset to gain the maximum energy efficiency. Which means to gain higher energy efficiency there is a trade off over a faster recovery time.

Hot water pipes not wraped and or exposed to cold attics, basements, crawl spaces or within cement floors, any and all of which draw out the heat from the water much faster in winters then in summers. Insulate exposed hot water pipes wherever possible.

Another possible cause that effects showers is the shower water valve itself. If it's a single handle type of mixit valve, it may be defective. Easy to detect that problem by the Do-It-Yourself person.

Here's How:
If no other part of the house, another shower, faucet or appliance has the exact problem, suspect the water faucet valve. In this case it may be necessary to change out or repair the water valve or faucet.

The last remote possibilities may also need to be verified by a plummer. Are the incoming lines attached to the water heater crossed? Are the two pipes coming out of the wall behind the water tank crossed?

Are there crossed pipes, at the effected appliance or hot water demand location, inside and or behind the walls, flooring, attic, basement or within the cement flooring?

If you need further assistance, use the reply button to add any additional information or questions, etc. Using this method also moves the topic back up to the top of the list automatically.

Regards & Good Luck. Sharp Advice
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First I have to ask why no dip tube??

How old is this gas heater?? Do you have hard water there where you are??

We have had water tanks that dont say make enough hot water and when we go to take them out 3 guys cant move a 30 gal tank . After years of build up from the lime and calcium around the flue pipe there from the water. The inside of the tank is not as big as it was.

Had a 80 gal HWT one time took 2 days to get out of the home the inside of it was like one big rock. They would run out of hot water also.;) ED

This is whats happening, if you was to draw hot water alone to the tub, as it's drawing cold water comes back into the tank and enters at the bottom of through the dip tube, by the time you draw 20 gals of straight hot water the water in the tank is now at the mixing point with the cold water, at this time the water is cooling down at a rapid pace, this 30 gal heater will not recover fast enough to keep up with the demand you want from it, now is the time up upgrade to a larger tank.

I have taken into consideration usage (no hot water used in the last few hours), cold weather (water line from outside buried, shouldn't matter), pipe insulation and runs (no insulation but only a few feet of pipe run).

There are a few unknows. The thermocouple (assumption is that they usually pass or totally fail), tank capacity reduced (flushed the tank but have seen evidence in the past of hard water scale ; white carbonate scale in the bath tub). The tank age is unknown but I am assuming that it is 6 yrs old.

I don't wish to buy a new tank now. A 50 gal tank would be oversized for our needs (probably 40 gal is right). Maybe the previous suggestion of upgrading to 50 gal was confused over use of litres versus gallons.

To simplify the question, why does a 33 galon tank deliver 10 gallons of hot water with the rest warm water?

Id ask what is the story on the dip tube? Where re what is it;) ED

As Ed is asking and I have overlooked,

What happened to the dip tube?

Why is it missing?

Or have you pulled the dip tube to see if it's even there?

This plays an important role in the operations on a water heater,

Just to add a note,

Say if the dip tube is there, it could be cracked in several areas, this would allow water to mix at odd intervals, this could be your case, where at time you have plenty and other times you don't.

No, I haven't looked. Was going to pull it when I worked on the plumbing.

Ball park estimates, 1/3 fill of a bath tube is approz equal to the capacity of the water heater. Based on the fact that it takes cold incoming water to push out the hot water, the dilution factor has to be taken into account.

In my opinion, the existing tank is too small for the demands placed on it. A larger tank is the only solution for the loads palced upon the tank. Aside from the fact that the dip tube may or may not be there or in good working order, the circumstances of capacity demand and potential supply are correct.

The existing tank is too small for the load and demands. A larger tank is required. A newer larger tank will also provide the energy efficiency to compensate for the replacement costs amortized over the service life of the new tank.

Ditto what Tom said.

This is what I was trying to say all along.

Thanks Tom