The Bummer for Tankless Water Heaters – Fixing a Scale Issue

Limitless hot water is nice! But this water pressure problem isn’t… Matt investigates a house with low water pressure and reveals the DOWNSIDE to a tankless water heater.

-Flow-Aid System DeScale Kit –
-Flow-Aid Solution 1 Gallon (enough to flush 2-3 units)-
-DeScale Video – Start to Finish Process –

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Ask This Old House plumbing and heating expert Richard Trethewey helps a homeowner replace a tank water heater.

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40 thoughts on “The Bummer for Tankless Water Heaters – Fixing a Scale Issue”

  1. Why not install a metal screen post heater to catch the large chunks that fall off the elements/tank of the heater.

  2. I think I'll stick with my system……just go down to the creek and jump in, then roll in the grass to dry off.

  3. perhaps I an dense. why is there no filter on the outlet side of the water heater? I would not stop the scaling or the low flow but it would prevent the scale from contaminating the entire system after the heater.

  4. In Lincolnshire we have really bad lime scale have to flush every 3 months . If it gets real bad they Pump hydrochloric acid round for half an hour

  5. Out here in well water country, the real problem is the water heater's inability to heat the water sufficiently to overcome the 40 degree temperature of the water when it comes out of the ground. Make sure you know what sort of temperature rise your heater is capable of above your ambient 'out of the pipe' temperature. The local hardware store sole several of the electric tankless models and every one was brought back because customers could only get about 88 degree water out of them because of the low ground water temperature.

  6. We have a tankless. We had a very good water softener and now we don't. We have had trouble since day one. No difference either way with or without a softener. Our water is very hard and salty. I'm looking into installing a hot water heater.

  7. Alternatively you can put in a scale inhibitor (sometimes listed as a filter, but it's not) before the hot water heater. Replacement cartridges can be purchased on Amazon for under $20 and only needs to be replaced 1 to 2 times per year. They use a food grade additive to prevent scale so its safe for drinking water. We have used one with our tankless for over 10 years and have never flushed it. No scale or flow issues since we installed it.

  8. You used raw plier jaws on chrome finish but used tape insulated jaws on brass hidden valve nut….scratches head?

  9. That happens in tanked water heaters, as well. Thats why tanks are supposed to be flushed once a year, but seems no one dose it.

  10. Am i the only person that thought of smashing out a piece of that concrete slab to fit the new heater in place..???

  11. Do you remove the plastic plugs that are sticking up out of the cold and hot water nipples?
    Awesome video. Thanks a lot.

  12. When you were preparing to move the old water heater out you had to move the gas pipe out of the way. Were you not worried that you would break the seal on one or more of the threads on the pipe?

  13. Just buy the least year warranty model and learn how to replace an anode. P.S. Make sure to drain the sediment in the tank yearly.

  14. The typical water tank .. the worst most purposely engineered inefficient fixture known !
    Imagine Big energy taking advantage of most peoples ignorance of the DISASTROUS MONEY wasting golden goose! ie.. 1. cold water released in a plastic dip tube without being preheated 2. around 180 -200 degrees pouring out the exhaust wasting MOST of the heat that is lit 3. A vertical exhaust pipe with heat rising into itself and not into the water horizontally 4. having connections on top of the tank 5. allowing heat loss to such an extreme level
    not to mention things like them importing a gas that isn't properly mixed with air so it burns very wastefully.

  15. If you check your video on timeline 3:41, you will see at the top of the water heater there are 2 nipples. One is for cold and one is for hot. Inside the nipple for hot is a white plastic plug and, in the cold, there is a blue plug.
    Are these suppose to be removed or, suppose to stay inside?
    I hope I made it easier for you to understand what I was talking about.

  16. just bought a new gas water heater and I would like to know if, I am suppose to take the plastic out that is in the nipples?
    Awesome video. Thanks a lot.

  17. 3/4 fittings coming out the top of the tank. Is there a problem if you reduce it to 1/2" through out your basement ?

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