The dip tube is a plastic pipe that routes incoming cold water to the bottom of the tank, where the heating elements (or burner) can heat it efficiently. When the dip tube breaks or detaches, cold water enters near the top of the tank and mixes immediately with the hot water — you get lukewarm output that runs out fast.
Symptoms of a broken dip tube
- Hot water runs out in 5-10 minutes (vs normal 25-40 minutes)
- Water lukewarm rather than hot
- Sudden onset (was working fine, isn\'t now)
- Small white/cream plastic flakes in faucet aerators (degraded dip tube material)
- The unit otherwise operates normally — burner fires, no error codes
How dip tubes fail
- Cracked or broken: plastic embrittlement over 10+ years
- Detached from cold inlet: friction-fit connection vibrates loose
- 1993-1996 manufacturing defect: some early-90s tubes had cross-linked polyethylene that degraded prematurely — well-documented industry issue. State units from that era often had recall coverage
DIY replacement
- Turn off power (electric) or gas
- Close cold supply valve at top of tank
- Open hot tap to relieve pressure
- Disconnect cold supply line at the cold inlet fitting on top of tank
- Unscrew the cold inlet nipple (typically ¾" hex)
- Pull out the dip tube (it\'s attached to or sits inside the nipple)
- Insert new dip tube
- Reinstall nipple with Teflon tape on threads
- Reconnect cold supply line
- Open cold supply valve; check for leaks
- Open hot tap until water flows steadily (purges air)
- Restore power/gas
- Wait 30-60 min for tank to reheat; test hot water duration
Cost
- Universal dip tube: $5-10
- OEM State/AO Smith dip tube: $10-20
- Pro replacement: $100-200 (often combined with anode rod inspection during annual service)
1993-1996 defective dip tube — class action
State units (and most AO Smith brands) manufactured 1993-1996 had defective cross-linked polyethylene dip tubes that degraded into small white particles. The class action settlement covered some replacements. If you have a unit from that era with the symptoms above, the dip tube is almost certainly the cause — and the particles in your aerators confirm it.
Bottom line
Hot water runs out fast + lukewarm output + sudden onset = dip tube. Cheapest water heater repair. $10 part, 30 min DIY. The plastic-particles-in-aerators symptom is the diagnostic giveaway.