# Tankless flushing and descaling



## rocksteady

Is there a particular pump that is recommended for descaling tankless heaters, or will any one work? I was thinking of using an old recirc. pump or something like that. Also, what do you guys use? At the last place I worked we had some commercially available mixture of chemicals but I've also heard vinegar works fine. I need to do mine at home but also want to gather the stuff I need to start pushing descaling/flushing for a few heaters I've installed in the past.





Paul


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## Tankless

I use a little pond pump. It's a bigger style and a higher quality but that's cuz I use it every week. I can flow about 2.5 to 2.8 gpm through the heater. I think I paid about 125 for it. I made up my own hoses as well. I was thinking of re-doing it a little. I have a bunch of grundfos pumps laying around and I think I could make some kind of bracket or something to mount on a bucket. I run a mix of CLR. It just depends on the water, the age the way in which the heater was being used (how high the temp was set to) and if there was a recirc or not. Latley I have been using a really strong mixes to try and get some of these heaters back from the dead. Vinigar isn't nearly strong enough, unless you want to flush the unit for 4 hours and replace the vinigar half way through. I got it down with CLR and how the color changes versus how calcified the unit was.

I would say no more than 3 or 4 gpm MAX.


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## rocksteady

Great, thanks. That's exactly what I needed to know. I realize it depends on the build up but about how long does it seem to take to descale a heater that hasn't been totally neglected?





Paul


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## Tankless

My typical is about an hour. I'll write up how I do them...it's the same for all tankless heaters. I gotta run right now./


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## Tankless

well, first things first. Know the unit you're about to work on. Know the error codes and how to find them. Have parts on you to make the flush easier (Iso valves...3/4" copper / fittings that sort of thing). Check the heater, make sure it works and like always never believe anything a homeowner says...they are F-ing liars. I offer them 2 ways to do the flush, one is the cheaper one...I show up and flush the unit and that's it. This is assuming they have iso valves. It costs X. Or I have the more detailed service where I flush the unit, pull the fan, gas mani system, clean the ignighter and flame rod(s). I also pull the servo valves and inspect them for proper movement. Pull the flow sensor and take it apart to inspect for damage. I also pull the venting and inspect the exchanger for condensate damage and corrosion in general. I'm looking for future issues with that one. I also check the manifold pressures and readjust as needed. This service cost X.

Can you imagine all the things I can learn by doing this? it takes less than an hour (well, now it does) and I very often wind up doing more than just a service. I've done prolly about 100 or so full service calls, and maybe 30 of the basic. Most of the basics are my installs that have soft water and a proper installation. When those things exist, there is no need to pull everything. When I walk up to this:









That's a different story. $600 for this one spent 3 hrs on it.









Make sense?


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## rocksteady

Makes total sense. :thumbsup: Thank you.


I'll be working on Rinnai's 90% of the time as that's what the supply houses stock around here. I'm sure I'll end up working on whatever crap Lowes sells since they just opened a store a few months ago here. We'll see how quickly the junk starts to surface. I've taken a Rinnai apart a number of times and replaced probably half a dozen heat exchangers, some solenoids and maybe 2 gas valves. I wouldn't even think of myself as a tankless expert but I don't feel overwhelmed inside a Rinnai anymore. The other brands? Not so much. I'm not afraid of them but I don't have service manuals for them and don't know the codes so I'm at a disadvantage when they show up but like I said, Rinnai's are what's installed in this area predominately. I think I remember you saying it's best to flush them with the power on and the gas turned off? Otherwise the solution bypasses the heat exchanger?

Nice manometer by the way. :thumbup:





Paul


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## Master Mark

*thanks for the info*



Tankless said:


> I use a little pond pump. It's a bigger style and a higher quality but that's cuz I use it every week. I can flow about 2.5 to 2.. I got it down with CLR and how the color changes versus how calcified the unit was.
> 
> I would say no more than 3 or 4 gpm MAX.


 
thanks for the information....

I have heard that CLR was not recommended on
those heat exchangers, 


I really dont have a clue..



You are the expert here, no doubt about it


here is the million dollar question

you showed one wheree you charged $600
to service and upgrade the unit....



what is your average service call to just de-lime a tankless heater and how often should this be done even with soft water???


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## Tankless

Master Mark said:


> here is the million dollar question
> 
> you showed one wheree you charged $600
> to service and upgrade the unit....
> 
> Installed new Isolation valve kit (cost to client 120, one hr. labor 85 and 20 in materials. So there is 225. Full service flush is 250. So there is 475. There was an 85 service call. I charge this every time someone tells me there is something wrong. If I get a "it's time for our service" call, I just charge them for the job, no service call. So 560 plus tax......Oh, there was an extra 30 bucks to tighten up his KS fixture. Nice guy, I tried selling him a softener, but he cried no money.
> 
> 
> 
> what is your average service call to just de-lime a tankless heater and how often should this be done even with soft water???
> 
> With a properly working softener I'd say every 2 maybe even every 3 years. No longer than that. Just cuz one has a softener doesn't mean scale won't build up, it totally will just not nearly as bad. Average service call is 150. I show up, flush the unit, check for error codes and flow rates when I am done. I will look for problems. That's my job really, I'm there to sniff out an issue in the making or one that has already started acting up. On an average call, my materials costs and wear and tear is about 20 per unit. This counts for pump time and the solution I make. So everything else goes under the mattress....oops, I mean the bank :whistling2:
> 
> Many, many times I get a call to flush a unit at the onset of problems. Client knew there was something wrong but just said it was time for a flush (hence my F-ing liars comment) and they wait till after I have started to tell me it's not working correctly, so now I just ask. I can usually tell. You see in that picture I had a hose connected up before any work was really done, I had it on the hot side to get the unit to error. I wanted to see how it fouled up. I do that on all of them. As for CLR or whatever solution...IMHO vinigar isn't strong enough. CLR works faster and better. Years ago I was told the CLR is hard on the rubber orings inside the unit. I have never seen one break on any heater so I am not worried about it. If one ever does break...I'll put a new one on. They are cheap to buy.
> 
> Here's what Noritz posted on the topic:
> 
> *Important things to remember when descaling a unit.*​
> 
> 1. Leave the *unit turned* *on and connected to power* during the descaling process.
> 2. Turn the *gas off* so the unit does not fire. An 11 code should result.
> 3. Check the inlet filter after the descale process. Debris flushed out of the heat exchanger may build up in the inlet filter.
> 4. Use only food grade vinegar or a solution of CLR or Lime Away diluted with 3 parts water.
> 5. After descale has been completed, flush the unit out with fresh water for at least 5 minutes or until 20 gallons have passed through the unit.
> Know the hardness of the water in areas you install in. If necessary set your customers up for a periodic descale. Please consult section 10 of the installation manual "Water Piping: Water Treatment" for details on water hardness and setting up a decaling schedule. ​
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three letters


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