We recently had a Bosch AquaStar Model 125B tankless gas water heater
It cost around $500 at Home Depot.
Sleek looking? Yes, definately.
Saves room? Yes, definately.
Well, here lies the problem...
Hot water only comes out when the faucet is all the way open and
Otherwise, if we turn down the water flow, it immediately becomes
and I MEAN COLD!!!
If we had known that's how these tankless water heaters operate, then
we never would have bought one.
So any savings in gas are eaten up by the huge volumes of water
necessary to get it hot.
Is this a joke or what???
We are seriously thinking of having the unit disconnected and returned
to Home Depot.
If anyone else has experienced this problem (or any others), I'd like
to hear about it.
We had one of those installed by a plumber last fall. I forget the
model numbers, but its a 125 something-or-another, and its the one that
requires no standing pilot and no electricity, it lights the pilot by a
small generator activated by the flow of water.
But anyway, we had a problem not unlike yours. The minimum flow rate
required to activate the unit was a bit on the high side, around 1 -
1.2 GPM, but the bigger problem was that temp rise was not constant
with water flow. Temp rise actually increased with increased water
flow. (I actually spent an hour one night at the basement sink timing
how long it took to fill a bucket of water and measuring the temp, and
I did that for a wide range of water flow rates.) The effect was that
when I took a shower in the morning, it wouldn't reliably turn on the
heater, and would usually go cold on me in the middle of a shower. A
new higher flow shower head solved the problem of going cold, however I
discovered that I needed to turn on the tub at the same time (tub and
shower have separate controls) to get the water flow up enough for it
to heat the water enough. I was getting only about 50 degree F temp
rise at 1.2 GPM or so, but at 2 - 2.5 GMP temp rise went up to about 75
degrees F, which gave me a good hot shower. Of course, its not
supposed to work this way, its supposed to be 75 degree temp rise
regardless of flow rate, but that's how our unit performed.
We did all the usual service things they suggested (which it didn't
need because it was brand new) with no effect, so we called the 800
number. First try with the 800 number got me a doofus who didn't know
squat about anything, and told me I needed to be standing next to the
water heater with a phone in my hand so they could walk we through some
items to test. And this is with me calling from work, so I would have
to go home, and besides I don't have a cell phone or cordless phone, so
I would have had to wire up a phone just to try out whatever it was
they wanted me to do.
So I waited a day and called back again, and randomly got a different
person who actually knew what they were doing. After about 2 seconds of
explanation, they told me I definitely got a defective unit, and they
will send out a new one right away. (With a deposit on my credit card
that would be refunded when the old unit was returned. )
Our plumber installed the new unit, and it functions better than the
old one, however there is still about a range of about 10 - 15 degrees
F temperature rise variation depending on the water flow. Its not
perfect, but it appears to be acceptable for our use.
We got this water heater on the recommendation of another person whose
unit appears to work flawlessly, however, we know yet another couple
who has one of the same units that was sinilarly defective and needed a
My suggestion to you would be to make a few measurements about minimum
flow rate required to trigger the heater (measure accurately with a
marked bucket and a watch with second hand), and then call the 800
number. (And cross your fingers you get someone who knows what they
are talking about.) Maybe they will allow you to try Russian roulette
and give you another unit to see if that one works acceptably. It
sounds to me lilke they let the consumer do the quality assurance
testing in their home rather than doing it at the factory.
Wow, im sorry to hear that. My wife would be chewing me out if that
happened. I been considering those but I guess I should probably not...
Funny thing is I have been considering the opposite as well. A Hot
water dispenser to replace the coffee maker for heating water.
"Then said I, Wisdom [is] better than strength: nevertheless the poor
I don't know if it's tough to find data on the dispenser idea, but it seems
it would save a lot of energy, considering the volume that must flow through
a water heater when the pipes have gone cold.
My parents had a tankless system on an oil burner for 35 years. That is
what was used 50 years ago. The original worked ok but when it finally went
bad the replacement was trash. They loved the water heater that replace it.
A simple way of operation is turning water on full , I have water volume
reducers on all spigots. My Ng savings are based on this. I agree 1/2
gpm or so may not trigger it to fire, it is just the way they operate
and something you must adjust to.
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