I have a 40 gallon Hotpoint gas water heater that will not get the water above warm I have it setting turn to hot.

call plumber to replace gas valve, it may cheaper replace water heater. gas valve is not DIY

Doesn't sound like its the dip tube, its a element problem, I would contact bw directly to see if heater is stil in warranty and they will send you new parts free.

the valve at the t-stat is no good, ist behind the cover at bottom of tank. drain tank to remove, make sure you shut of gas and power first.

You have 240volt electric water heater
Check both elements for leaking.
Check top of tank for leaking pipes.

If water heater is leaking from side of tank, then tank is rusted out and could rupture.
This tank must be replaced.
http://waterheatertimer.org/Water-at-bottom-of-water-heater.html
My friend welded his tank to get more life out of tank, but he assumed the risk.

Hot water heaters are under pressure from heated water which expands.
If tank ruptures, water will flood out of tank and water will run until shut-off is turned OFF.
This causes major damage inside home.

Protect yourself first, and then let's talk more.
1) Turn off water at shut off located on cold water line above tank.
2) Turn off power to water heater:
Gas heater, rotate valve to 'pilot' so pilot is lit but burner does not turn ON.
Electric heater, turn off circuit breaker.
3) Open tub spout on hot side and let run a bit to relieve pressure.
4) Now your property is safe.

You can limp along with failed heater if leak is slow.
Turn heater ON when you need hot water.
Typical Gas heater makes 41 gallons hot water per hour.
Typical Electric heater makes 21 gallons hot water.
Shower uses 5-9 gallons hot water, bath uses 12-14 gallons hot water.
http://waterheatertimer.org/images/Water-heater-reference-guide-2.jpg

If you are going to install heater yourself:
Look at label on side of old tank to identify size and particulars.
I buy ordinary heaters from Lowes and Home Depot and always buy scratch-n-dent models when possible, because superficial damage to outer tank does not lower lifespan of heaters I have installed.
Buy same size heater if it worked fine before.
Buy new flexible water connectors.
Set water heater in drip pan.
Offer 10% less than price shown. Make them deal with you. Shop Ace hardware, Lowes, Home Depot. Kick the tires since you have a bit of time.

I know you have electric heater, but many folks read these answers, so I include info on gas too.
#1 rule) tankless heaters are a rich-man's toy, because tankless will never pay you back, and will become major money pit if you encounter 1 repair. Electric tankless heaters require larger electric service box. Gas tankless require larger gas line (larger gas line, more gas consumption, bigger bill unless you cut consumption)
2) How to install gas heater:
http://waterheatertimer.org/How-to-replace-gas-water-heater.html
3) How to install electric heater:
Read link above because many of same steps apply to electric.
The difference with electric, is turn off power, disconnect wires, and reconnect wires exactly like before. Set electric heater directly on insulated surface like dense blue styrafoam. Cut styrafoam in circle so it fits inside dip pan. Wrap entire electric heater with insulation blanket, except don't cover TP valve.
4) Connect bare copper jumper wire between hot and cold pipes to prevent stray current corrosion which will shorten life of tank. Make sure cold water line is grounded.

Also read:
http://waterheatertimer.org/9-ways-to-save-with-water-heater.html

Add a comment for more free assistance.
Also take advantage of fixya phone service.
For a price, fixya expert speaks to you via phone about any do-it-yourself problem.

A leaking water heater cannot be repaired, assuming it's the tank leaking and not nearby water pipe.
http://waterheatertimer.org/Water-heater-leaking.html

First thing is to protect your property from catastrophic tank failure where tank ruptures and water runs until it is shut off:
Tanks are under pressure when they are hot.
Close cold water shut-off located above tank.
Turn control knob to 'pilot' so pilot is lit but burner will not turn on.
Open hot side on tub for few moments to relieve tank pressure.

Now your property is safe.
You need a new water heater.
In mean time, gas water heater makes 41 gallons hot water per hour.
Shower used 5-9 gallons hot water.
Bath uses 10-15 gallons hot water.
You can turn on water heater for short stretches and limp by until you get a new heater.

Steps for installing gas water heater:
http://waterheatertimer.org/How-to-install-gas-water-heater.html

I wrote a page on leaking water heaters with resources and information:
Page lists things to check.
http://waterheatertimer.org/Water-at-bottom-of-water-heater.html

Also run hand over tank to find warm spot that says where leak is coming from
A rusted tank cannot be repaired.

If your tank is rusted out, it might burst open and flood the area.
Hot water inside tank is under pressure.
Turn off heat source to water heater.
Turn off water valve located above tank.
Open tub faucet on hot side and relieve pressure from tank.

You can limp along with a leaking water heater by turning it on when hot water is needed.
For example a shower uses 5-9 gallons hot water.
Turn gas water heater on for 15-20 minutes.
Turn electric on for 20-30 minutes.

To conserve resources with next heater:
http://waterheatertimer.org/9-ways-to-save-with-water-heater.html

If you'r really lucky you may find a leaking fitting on top of the water heater thats draining down inside the shell and out the bottom, otherwise its time to replace a rusted out water heater.
Sorry

For images and product information
For manual


You checked ohms, did you check for 240V across lower element when lower element is turned on?

Energy smart electric water heater has a control box on top of unit. Water heater does not have typical thermostats that can be tested and replaced. Temperature sensors located above each element send information to control box through small black and red wires. Temperature sensor sells for about $40, but there is no test listed that shows how to determine when sensors fail.

Potential problems:
-Temperature sensor is not reading correct temp
-Control box not processing correct temperature information
-Selector on control box set to 2, 3 or 4
-Thermostat temp on control box set lower than 120 degrees F
-Sediment build-up starting to surround lower element so water doesn't circulate (see if drain valve runs full-open

Check the gas is on.
Check the pilot is lit.
Check that the valve is set at a high enough heat setting. The disc on the front of the gas valve. It may be set to "vacation" in which case nothing will happen untill you turn it to a warm setting.

How big is your bathtub? Is your water heater set on the hottest setting? What is the temperature of the hot water at the tap?

Keep in mind that hot water can cause severe burns. Children and those with diminished mental capacity can be seriously harmed by hot water.

The "40 Gallon" rating on the water heater is usually the amount of hot water the unit can produce in one hour. So the tank, and the amount of immediately available hot water, might be smaller than 40 gallons.

My bathtub is 2 feet wide by 1 foot deep and 4 feet long. This is 8 cubic feet or almost 60 gallons. So a 40 gallons of water at 120 degrees, mixed with 20 gallons of cold water (60 degrees), fills the tub with 100 degree water. My January cold water is 42 degrees, so it will take 40 gallons at 129 degrees to fill the tub. If the tub is cold to start it will take even hotter water.

So the water heater might be just fine.

Possible solutions:
1. turn the temperature up on your water heater- or the temperature control could be malfunctioning and not getting the water hot enough.
2. insulate your hot water pipes so that the water loses less heat on the way to the tub.
3. bigger water heater.
4. smaller bathtub, or less full bathtub.