I have low water pressure from the hot water. i have a power star instantaneous water heater.

If it is under warranty, just contact the company to diagnose and fix it. The most likely cause is a failed thermostat or element, but as the flow rate is also incorrect, it may be a control board issue. This unit only seems to be available in Australia. We are in North America :>)
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It sounds as though you need a plumber...

It sounds as though the cold water feed pipe is a low pressure supply from a storage tank (rather than the mains) and something has become blocked or displaced.

The pipework needs tracing to locate the fault and rectify it as the heater will need a good continuous supply of water if it is to function properly. If it is an instantaneous type heater check with the instruction manual as that type of heater often need a high pressure supply.

Clog in hot water line?

Replace heat trap nipple at top of water heater?

http://waterheatertimer.org/Low-hot-water-pressure.html

http://waterheatertimer.org/Whirlpool-Energy-Smart-electric.html

http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent

http://waterheatertimer.org/New-water-heater-making-noise.html



Gene

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

http://waterheatertimer.org/Low-hot-water-pressure.html
Link above have general troubleshoot steps to determine possible causes of low pressure

Gene

Water Heater Timers Save Money

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

blah blah blah

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Hello Mike,
Check gas pressure, burner parts need to be cleaned, check electrical outlet, hot surface igniter is bad

White Rodgers intellivent error code:
http://waterheatertimer.org/How-to-adjust-water-heater-temperature.html#Intellivent
http://waterheatertimer.org/pdf/Intelli-vent-gas-valve2.pdf

Error code says: system in lockout, but you know that.
1) Low gas pressure, no gas to water heater: call gas company to check pressure
2) Hot surface igniter not positioned correctly: inspect and clean burner parts.
http://waterheatertimer.org/images/Reliance-hot-surface-ignite.jpg
3) Low voltage to water heater/ outlet has wrong polarity: Use circuit analyzer on electrical outlet to make sure polarity is correct

Typical power vent manual:
http://waterheatertimer.org/pdf/Reliance-40-50-power-vent.pdf
Cleaning water heater:
http://waterheatertimer.org/How-to-install-gas-water-heater.html#clean
http://waterheatertimer.org/pdf/How-to-clean-combustion-chamber.pdf

We probably need more information to give a good answer.
You report 2 different problems occurring at once: Low pressure and Low temperature.
If this is tankless water heater, then Low pressure and Low temperature might be related, and you probably need a service technician to diagnose and repair cause.

If this is tank-type water heater, look at label on side of tank for type and brand of heater.
Is it gas or electric water heater? Troubleshooting is totally different for each.

Is water pressure pressure low on just the hot side faucet, or is cold side faucet affected too?
Are all hot faucets affected by low pressure?
If you have a dual handle faucet, open hot side only and check if hot water that comes out is hot as normal.
This will say if problem is pressure or temperature.
Tank-type water heater usually won't have both these problems occur at one time, but water heaters work in funny ways sometimes.

Add a comment to this post, or re-post your question with details so the experts can give a solid answer and not guess.
Also you can post water heater questions on pro water heater forum:
http://www.thetankatwaterheaterrescue.com/forums/forum3/

Add a comment for more free help.
Also take advantage of fixya phone service.
For a price, expert speaks with you over phone while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

Not sure but check the inlet water at the heater, the filter may be clog up a little that restrict the flow. Did u use the heater at all during the winter? If not, the heat exchanger may be clogged with built up in there. U need to descale it. Good luck. Chinhcu

I have a triton opal shower.

I turn shower on low pressure and cold water. then no low pressure and piping hot water for a very short time then low pressure and cold water.

I've changed the solenoid and the little black plastic ball.

Help !

I wonder if you have this problem below caused by a drop in water pressure from someone flushing a toilet or a washing machine. I would call the company to remedy this issue.

17. What is a cold water sandwich effect? The term “cold water sandwich effect” is a term that is used to describe the introduction of cold water into the hot water supply line during frequent on/off operation of an instantaneous water heater. The cold water sandwich effect, when present, appears as a momentary drop in hot water temperature as it is discharged from a hot water supply outlet (i.e. shower, tub, or faucet). This phenomenon is present in the operation of all instantaneous, tankless style, water heaters, but is minimized with the high tech design of Rinnai water heaters.
The technology built into the Rinnai water heaters is designed to minimize the cold water sandwich effect. Rinnai water heaters are microprocessor controlled and when water flow through them ceases, they remain in a “ready to fire state” for approximately 1 minute. If water flow through a Rinnai water heater begins within the first minute following water flow stoppage, the water heater will fire back up within 1 to 2 seconds. This minimizes the cold water sandwich effect that would otherwise be experienced with a low tech tankless water heater. It should be noted that the cold water sandwich effect cannot be removed completely from tankless style water heaters. The safety standards developed to insure the safe operation of water heaters require a delay in the ignition sequence of all gas water heaters.
While the cold water sandwich effect cannot be completely eliminated from standard plumbing systems, it can be eliminated from plumbing systems that have a supply and return hot water circulating system. Rinnai has developed 2 methods to eliminate the cold water sandwich effect in residential hot water circulating systems.
The first (and preferred) method to remove the cold water sandwich from circulating systems utilizes a small electric tank water heater (powered up) that is used with a dual purpose. The small water heater acts as a mixing tank to eliminate the cold water sandwich effect from the Rinnai water heater and it uses its electric heating element to offset the heat losses from the hot water circulating system.
The second method to remove the cold water sandwich from circulating systems utilizes a small 2 to 6 gallon storage tank installed on the hot water outlet of the Rinnai water heater. This tank acts as a mixing tank to blend the cold water sandwich with hot water and eliminating its effect at fixtures.