skip to main content

Water hardness and flushing tankless water heater question

5 years ago

We are new to tankless water heaters. We have been in our new house for a year now. We have a Rinnai propane tankless. We are on well water. We have a sediment filter but no softener. I don't think we have hard water. Water testing showed total hardness at 19 Mg/L. Is there any other numbers on the water testing I have to look at to determine water hardness or just the total hardness number?With 19 mg/L how often do we need to flush the water heater?

Sort by:Oldest

Comments (4)

Jake The Wonderdog
5 years ago
19 mg/L converted to grains per gallon is ~1.1 gpg. Looking at this Hardness Scale you have "Slightly Hard" water.

I would guess you could go easily 2 years - but not more than 3 years - between cleanings. Some of this depends on the amount of hot water you use and the temperature you have the heater set for.

Was it installed with service valves? If you don't know, then snap a photo that shows the bottom part of it and post the photo.

Know that cleanings are easily something that most can do themselves if there are service valves.
vinmarks
Original Author
5 years ago
Thanks Jake the Wonder Dog. We have the tankless set at 120. It's usually just me and my husband here most of the time and 2 college age kids here on holidays and during the summer. Yes it does have service valves and we were able to clean the little inlet filter which didn't have anything in it. I'm pretty sure we will have no problem flushing the tankless. I watched a video from Rinnai. I just wasn't sure how often we needed to do it with our water hardness value.

I see a submersible pump is needed. How powerful does the pump need to be? We have a Harbor Freight near us so I can look there for one.

So with the information I gave you do you think every 2 years would be good for flushing the tankless?

Thanks for your help.
Related Discussions
any hints for flushing a tankless water heater
Q
Comments (3)
A bucket, 1 gallon of white vinegar, a small submersible "floor sucker" in a bucket, 2 washing machine hoses and hopefully he has the service port valves with flushing hose bib attachments that allows you to isolate heater from water supply while pumping solution through heater while it is off. Why are you flushing? Did he record the rise through the exchanger when new and it has increased 3-5 degrees since new? All this is available on a quality heater with the remote control.
...See More
Tankless Water Heater: GPM and Incoming Water Temp Questions
Q
Comments (4)
I'm a bit late to respond but I'll give you my input on how our Noritz M-084M is working in Sammamish (Seattle area), which is to say, great! The 8.4 GPM is for a 45 deg temp rise, the lower 5 or 6 GPM is for a higher temp rise needed in Winter. You can find the charts on the Noritz website. I have our unit set to 120 deg and it works well at that setting. Our kitchen is the farthest from the unit, which I installed in the garage attic, and with the temp set at 120 I run the faucet on full hot when doing hand washing of dishes and this is just fine. I find the unit actually works better with COLDER incoming water temp. In the summer the temperature at the kitchen seems to be lower for some reason. The highest load we put on the unit is running two showers at once, which we do on the weekend. It has absolutely no problem keeping up and the water temp stays nice and constant. Our unit is rated at 0.75 GPM to activate, and there is no problem at all to get it running with a bath faucet. Newer units are 0.50 or below. And once it's running it seems like you can turn it down below the 0.75 GPM rate and still get hot water. Go too low though and it will shut off and you'll get the dreaded slug of cold water. This happens very infrequently and has not been any problem. If you haven't purchased a unit and would like to see our installation, drop me an email. I have some pictures or you could come out and take a look in person. Tom
...See More
Has anybody ever flushed their tankless water heater?
Q
Comments (14)
Hi Lisadlu, I guess it went fine....The water went in and it came back out. I didn't really see too much dirty "stuff" in the vinegar bucket, or the rinse bucket at the end. I think there was a little red residue in the rinse water which I think was the from the HOT water hose (it was red). Due to the low amount of "Stuff," either I didn't need to do it, or I didn't do it right. I had read somewhere NOT to turn off the electric, but the instructions in my manual clearly said to turn it off, so I did. I was lucky to have the valves already installed by the original installers. It just made sense to shut off the cold in and hot out, and then attach the hoses and run the cycle of vinegar for an hour or so. I guess the plumbers charge so much because of the time, not the technicality. I wasn't too clear on the rinsing part. I let the cold water run in to the heater and out into a clean 5 gallon bucket, then emptied it and let the 5 gallon fill one more time. I think I was supposed to let that 5 gallon rinse run through a few times, but I didn't see the point. I just let the hot water faucets run for a while. There was a slight vinegar smell when I first turned them on. I did it all by myself! No hubby required. I watched a few videos and consulted my owner/installer manual. I made sure to do it on a Monday and not a Friday in case I @#%$'d it up! (figured emergency plumber on a weekend would cost $$$) Good Luck!
...See More
water pressure question with tankless water heater
Q
Comments (17)
updating to let you know that we did install a whole house booster pump and it has been very positive. Overall, our water pressure thoughout the house is MUCH improved and becase the demand is greater at the faucets, the heated water arrives quicker. The kitchen, sink, however, is still considerably slower and cooler. It's so weird, and I really cant decide what the actual probelm is (our house is on a slab, so no way to do anything with the pipes at this point) so we are going to install a small, 6 gallon, hot water heater under the sink so that I can have instant hot water. Warm water does not work at a kitchen sink - you defintely need hot water. The line will be tied in with the regualr hot water so if I am using lots of hot wter, by the time I use up my 6 gallons, the 'regular ' hot water will be there. I will come back to update after we get it. I know all of this sounds like an expensive overkill, but it is worth it to me to get the level of performance I orginally wanted.
...See More
Jake The Wonderdog
5 years ago
Yes, I think you would be fine every 2 years.
The pump is small and cheap - 1/5 - 1/3 hp with pickup on the bottom and a 3/4" hose connection. The hoses are cheap washer connection set and a 5 gal pail. You will buy a couple 1 gal jugs of vinegar at the grocery store. I keep my kit altogether (except the vinegar) near the heater so I can find it.

You can order a complete kit but it's cheaper to buy the parts.
vinmarks thanked Jake The Wonderdog
vinmarks
Original Author
5 years ago
Great thanks for the information.

Related Stories

GREAT HOME PROJECTS How to Switch to a Tankless Water Heater

By Mariana Pickering (Emu Building Science)

New project for a new year: Swap your conventional heater for an energy-saving model — and don’t be fooled by misinformation

BATHROOM DESIGN Water Damage Spawns a Space-Saving Bathroom Remodel

By Mitchell Parker

A game of inches saved this small New York City bathroom from becoming too cramped and limited

GREEN BUILDING Water Sense for Big Savings

By Bud Dietrich, AIA

Keep dollars in your pocket and preserve a precious resource with these easy DIY strategies

SAVING WATER 11 Ways to Save Water at Home

By Carol Crotta

Whether you live in a drought-stricken area or just want to help preserve a precious resource, here are things you can do to use less water

LIFE The Top 5 Ways to Save Water at Home

Get on the fast track to preserving a valuable resource and saving money too with these smart, effective strategies

HEALTHY HOME How to Choose a Home Water Filtering System

By Laura Gaskill

Learn which water purification method is best for your house, from pitchers to whole-house setups

GREEN DECORATING Easy Green: Big and Small Ways to Be More Water-Wise at Home

By Laura Gaskill

These 20 tips can help us all make the best use of a precious resource. How do you save water in summer?

DISASTER PREP & RECOVERY Remodeling After Water Damage: Tips From a Homeowner Who Did It

By Judith Taylor Designs

Learn the crucial steps and coping mechanisms that can help when flooding strikes your home

GREEN BUILDING Just Add Water: Rain Barrel Magic

By Marianne Lipanovich

Take your rainwater storage from practical to beautiful with a new breed of design-friendly rain barrels

LANDSCAPE DESIGN 10 Ideas for a Creative, Water-Conscious Yard

By Laura Gaskill

Check out these tips for a great-looking outdoor area that needs less water

Sponsored

Dave Fox Design Build Remodelers

49 Reviews

Columbus Area's Luxury Design Build Firm | 17x Best of Houzz Winner!

More Discussions

Need help identifying a bathroom faucet.

0

Shower faucet system

3

under mount sinks -faucet types

1

Upgrading tub from a shallow surround to a soaking tub. Recs please

11

Fotile In-Sink Dishwasher

0