# Flushing A Tankless



## Titan Plumbing (Oct 8, 2009)

I am scheduled to flush a tankless on Monday, it has not been flushed since it was installed approximately 4 yrs ago. Because of this I've chosen to use muriatic acid. 

I do not have one of those neat little flush kits, I've put together my own, it consists of a 5 gal food grade bucket, washing machine hoses and a sump pump...My question is, is there a preferred flow rate to flush? The pump I have is 1/6th HP and pumps 900 gph. Does this really matter? I know it's recommended to flush for 45 minutes.


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## DesertOkie (Jul 15, 2011)

900 gpm? I need one of those for draining water heaters.


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## myakka (Jun 15, 2011)

bring ice to keep it cool


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## Titan Plumbing (Oct 8, 2009)

DesertOkie said:


> 900 gpm? I need one of those for draining water heaters.


I know, after I bought it, I was like...


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## cbeck (Mar 7, 2012)

900 gpm?! I have the Flow-Aide Descaler kit and the pump is 500gph.


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## studmaster1 (Dec 10, 2011)

Check with the Manufacturer to find the best one for the job, and what descaled to use. Rinnai will void any warranty If you use anything but white vinegar. A teel pump should be able to do the job, and they recommend covering the outlet with a sock or filter to help keep the crap out.


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## Titan Plumbing (Oct 8, 2009)

LOL!!!!!!! Okay...so who says I'm slow or stoopid....Had a rough day...*it's 900 gph*...

With the correction, is that too much?


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## gear junkie (Jun 20, 2008)

I wouldn't use muratic acid. I wouldn't trust myself to able to flush it out well enough. I use straight vinagar in mine. I think my pump is either the zoeller 1/6 or 1/4 hp. Turn on the tankless briefly(20 seconds) while flushing to "pop" the scale off. Do this about 10 times while flushing. You'll hear the difference and see the sediment come out when you do this.


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## rjbphd (Feb 5, 2010)

Sell them a tank heater... less maintence...


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## cbeck (Mar 7, 2012)

Noritz recommends the power to be kept on, but the gas turned off while flushing


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## Gettinit (May 9, 2012)

It needs to at least be NSF 61 rated to cover your a$$ legally. As far as warranties go, many warranties are voided if proper maintenance has not been done. rheem is one of those manufacturers. Pump choice is big. I recommend a diaphram pump because it is cheaper than a magnetic pump. At least use an in line filter before your pump or you will blow the seals. Vineger is only good on calcium. That being said if it breaks anything loose it will likely get lodged somewhere you don't want it. If that doesn't happen it never came off in the first place and what good did you just do?


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## ZL700 (Dec 8, 2009)

I doubt that flexible gas connector and valve have the BTU capacity required for that tankless.


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## Titan Plumbing (Oct 8, 2009)

I think I'm going to scrap the idea of using muriatic acid. I'll try CLR or Lime-Away...


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## GREENPLUM (Jul 27, 2008)

Titan Plumbing said:


> I think I'm going to scrap the idea of using muriatic acid. I'll try CLR or Lime-Away...


 
white vinegar is all ya need, scrap the rest


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## Gettinit (May 9, 2012)

GREENPLUM said:


> white vinegar is all ya need, scrap the rest


Respectfully disagree. I have used hot vinegar and ran a different solution behind and it was mind blowing how much it missed. 

I will add this, some of these acid mixes are REALLY BAD on stainless steel heat exchangers. I am sure someone on here knows what that hard fungus like growth is that occurs but I can't remember.


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## SewerRatz (Apr 25, 2009)

Titan Plumbing said:


> I think I'm going to scrap the idea of using muriatic acid. I'll try CLR or Lime-Away...


I use Flo-Aide which is a food grade phosphoric acid, you dilute 1 jug of the Flo-Aide to 4 jugs of water. This stuff has gotten choked up heat exchangers flowing like brand new in no time. Its also the same ingredient that A.O. Smith uses in their Un-Lime product for descaling tank water heaters, and their boiler tube style heaters.



cbeck said:


> Noritz recommends the power to be kept on, but the gas turned off while flushing


I had the pleasure of a Noritz tech come to a job site to help me trouble shoot a few units. He informed me that the reason you have the gas off and the power on, is the heater will go into a descaling mode when it flashes the error 11 code from not able to lite up.

As for the pump, as long as the heater is left powered on and the gas turned off, the heater will go into maintenance descaling mode. which will open the flow control valve to a point to regulate the flow. So no worries about the flow rate. Key though is to have a pump strong enough to flow the .5 GPM to activate the unit.

The classes I took for Rinnai, Takagi, and Noritz all said to turn off the gas and leave the power on, to descale their heaters.


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## johnlewismcleod (Apr 6, 2012)

Wut Ron said :thumbsup:

I've been told by enough different manufacturer tech's that the descaler solutions formulated for tankless work better than vinegar or whatever that I now believe them.

Stick with a tankless descaler solution and pass the cost on to the customer.

I made up my own pump/bucket rig like you did, just don't let you pump set down on the bottom of the bucket :no:...you want it elevated so the scale solids can settle out and you're not constant recycling them through the unit via the pump :yes:


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## victoryplbaz (May 19, 2012)

Your asking for trouble with the acid..All one home owner has to do is see it. Then think they can do it and bam! Law suit time.


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## Gettinit (May 9, 2012)

victoryplbaz said:


> Your asking for trouble with the acid..All one home owner has to do is see it. Then think they can do it and bam! Law suit time.


That's why you look for NSF 61.


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## bizzybeeplumbin (Jul 19, 2011)

I use flow aide, have been for years, one bottle, one gallon. Depending on which tankless you are flushing, you need to know how to get the bypass valve open or you will only flush the bypass line and miss the exchanger, this is why noritz stays on with gas off, and why Rinnai gets lowered to 98 degrees and run for a minute then the power pulled on it. And with noritz if they are about give you a warranty exchanger they better see that code 11 pop up on the maint monitor. shows its been flushed properly. 

I will not use vinegar, waste of time in my opinion. Ron, I respectfully disagree with the power being left on to a Rinnai while flushing it.


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