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cjteter · Jun 2, 2009, 04:58 PM

There is a very loud and increasingly more frequent knocking of pipes in my wall. It seems to be coming from the water heater and vibrating through the pipes. I've tried draining the heater with no change. The knocking doesn't seem to be associated with using water, hot or cold, as it will be knocking when I walk in the house from working all day. And, the sound stops if I turn on a faucet, so I've been forced to leave water running all the time to get relief for the knocking... HELP!!

massplumber2008 · Jun 3, 2009, 04:37 AM

Hi cjteter:

You drained the heater, but did you POWERFLUSH the water heater..

If your water heater has sediment built up in the bottom of it then draining simply will not be enough to loosen/remove the sediment. Here, you will need to leave the water pressure on full and then attach the hose to the drain as you did last time but this time just open the drain fully and let the water flow from the heater for 15 minutes or so to POWERFLUSH the sediment away.

The DIP TUBE in the heater will help to direct full water pressure into the sediment layer at the base of the heater and with any luck loosen the sediment and wash it out the drain outlet.

If a heater has never been flushed this way then I will usually PULSE the shutoff on and off as I go along a bit... let some water drain out and then turn water on full pressure again. I keep cycling this way to help loosen the bigger chunks that may be difficult to break up.

Finally, after all this you will want to open a hot water faucet WITHOUT AERATOR in place and purge the pipes of any sediment that may enter the pipes. A two handle faucet is best or a laundry faucet in basement is even better. Then go around and clear all the other faucets to be sure all is good! If any issues pop up at any faucets you should just need to remove the aerator and clean to fix.

Let me know if you have questions...

MARK

Milo Dolezal · Jun 3, 2009, 06:34 AM

It sounds like Thermal Expension problem to me. Install Thermal Expension Tank and see if that helped.

cjteter · Jun 4, 2009, 05:53 AM

Ok, so, I did what you explained for the water heater, along with shutting off the main water, turning on all the faucets/flushing toilets, etc. to empty all the water out. I was told that the sound may be air in the pipes. I turned the water main back on and let all the faucets run until they stopped sputtering. That seemed to do the trick... for about 4 hours. Now they are knocking again, randomly, in the middle of the night, etc. What's left? Do I need to adjust the pressure? Should I try the air thing again?

Milo Dolezal · Jun 4, 2009, 05:58 AM

You may have Thermal Expension. What temperature is your water heater set on ? Set it to 120F.

speedball1 · Jun 4, 2009, 06:03 AM

Is your water heater gas or electric? Tom

cjteter · Jun 8, 2009, 05:48 PM

The heater is gas.

Milo Dolezal · Jun 8, 2009, 05:49 PM

Turn down temperature at the water heater thermostat to 115F. See if it the noise continues...