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Old 04-10-2008, 08:30 AM   #1
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gas water heater testing


I have two gas water heaters. Both are 50 gallon, about 5 years old.

One seems to perform fine.

The second one does not seem to delver hot water very quickly... it
takes several minutes of running the hot water to get hot water to
actually come out... . The tank is right above the faucet, so it doesn't
seem like that path the water would go is very far. The temperature
on the 2nd unit is set hotter than the first unit, but the 2nd unit seems
to run out of hot water faster....

I compared my gas bill ( this is my first house with gas ) to a buddy
at work... We used the gas heater ( for room heat ) some this month, but
not a lot and we used 2x as much gas as he did..... our electricty usage
was about the same.... 1200kwh. I used 6mcf and he used 3mcf for the
gas.

I know with electric water heaters, there are dual elements and
(sometimes ) dual thermometers that need to be replaced... not
sure about gas... I'd bet $$$ that neither water heater has been
drained ever....

Any thing I can look for / do before I call a plumber...

Thanks - jack

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Old 04-10-2008, 07:05 PM   #2
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gas water heater testing


The water heater just makes water. It has nothing to do with the time it takes to deliver water to a faucet. I take it there heaters are not located next to one another? Are you sure the faucet above the water heater in question isn't in fact tied into the further water heater? And you're sure the plumbing doesn't go through some strange route feeding that faucet last? Do you have a re-circulating line even if it is currently unused?

The only way for one water heater to physically loose volume is to fill up with sediment. It is possible that your water heater has a lot of sediment in it. It is also possible for one to get more sediment but they should be fairly close.

Comparing gas bills is very difficult. Remember that you have two tanks and he probably only has one. Even if his is larger one 100 gallon unit will use less gas than 2 50 gallon units. Then it depends how much hot water the heaters get. It's pretty cheap to keep hot water sitting in the tank but start taking 3 showers a day, doing laundry, dishes, washing your hands, etc and the water heaters start working and consuming more gas. You also used a gas boiler or furnace as you said. Water heaters do loose efficacy as they fill with sediment though.

First look at your hot water lines to be sure they're run correctly and aren't doing some wacky thing running different corners of the house. The next is to flush your water heaters. Do a search on that here or even Google and you'll find some good writeups. I'd be prepared with brass caps on hand for the boiler drains on the water heaters as sometimes they won't shut fully once you open them. For $2 it's good insurance.

If you have to replace the heaters which you shouldn't as they're not too old consider installing one larger unit in a central location or at one of your current locations with a re-circulating line. If you really use a lot of water an 80 gallon tank should be plenty, most homes only have a 50 or 60 gallon tank.

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Old 04-10-2008, 10:20 PM   #3
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gas water heater testing


It sounds like the dip tube is damaged. This will cause the cold water to flow directly from the inlet to the outlet without mixing with the hot. The dip tube is on the hot water outlet and extends to the bottom of the tank to draw the hot water from there.
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Old 04-10-2008, 11:05 PM   #4
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Quote:
Originally Posted by Gencon View Post
It sounds like the dip tube is damaged. This will cause the cold water to flow directly from the inlet to the outlet without mixing with the hot. The dip tube is on the hot water outlet and extends to the bottom of the tank to draw the hot water from there.
That's a good point. If flushing doesn't help you and the pipes are run correctly pull the dip tube and inspect it.
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Old 04-12-2008, 07:35 PM   #5
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gas water heater testing


Hi guys:

Hey...in my area dip tubes are installed on cold water inlets. See pic.

The idea is that cold water is introduced at the bottom of the heater where it can be heated and rise to the hot water outlet. It also aids in flushing the water heater.

Just wondering. Let me know.
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Old 04-12-2008, 07:45 PM   #6
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Quote:
Originally Posted by Boston Plumber View Post
Hi guys:

Hey...in my area dip tubes are installed on cold water inlets.
Problem is often times their isn't enough room to pull out or installed a new dip tube without disconnecting the heater and leaning it over.
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Old 04-13-2008, 10:06 AM   #7
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lol, good pic Boston! My bad. You are correct, of course!

Either way, I think the dip tube may be the problem. Sometimes you do have to lean the heater over to replace it.
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Old 04-13-2008, 10:15 AM   #8
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Quote:
Originally Posted by Marlin View Post
Problem is often times their isn't enough room to pull out or installed a new dip tube without disconnecting the heater and leaning it over.
Hi again guys....Hey Marlin...never suggested anything about replacing...just wanted to point out that dip tube was on cold water side.

In terms of replacing dip tube, sometimes need to drain heater and tip heater over...sometimes don't. Either way, poster needs to cut the cold water pipe, remove nipple and see if can pull that dip tube out. As in my pic. above, dip tube should be within 6 inches to 1 foot of bottom of heater...if not, if say 1/2 way up, or simply can't find under nipple (meaning dip tube fell in/off) then need to replace the dip tube.

I just didn't want the poster to pull the hot water nipple/pipe is all...good day all.
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Old 04-14-2008, 08:28 AM   #9
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Thanks guys... I still haven't done anything with this yet.... more symptoms...

on one sink, I have to run the water for 60 seconds before I get hot
water.

on one sink.... ( different time of day ) I have to run the water for 10
seconds before I get got water. I'm pretty sure that those are on different
water heaters... but I'm not 100% sure.

Both water heaters are identical models. They were installed at the same.
They are both Gas units. They are about 50 feet apart, installed in the
Attic. Both are about 5 years old... and both were turned off for over
a year. I don't know if they were drained or if they were full while
they were turned off.

The 'good' water heater is on the 'middle setting' and it's got good
hot water and starts giving hot water after 10 seconds or so. The 'bad'
water heater was on the 'middle setting +1' and it the water was hot...
but not that hot... not as hot as the 'good' one... I have moved it to
'middle setting +2' and it does provide hot water, but... it takes a
minute or so to get going....

I plan on turning off the 'bad' water heater and draining it. I'll be able to
figure out what systems are fed off of which water heater.

Before I cut any pipes and look at the dip tube... this is in my attic so it's
not real easy to work on.... is there an easy way to figure out if there
is a lot of sediment build up inside?

Thanks - jack
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Old 04-14-2008, 12:03 PM   #10
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Quote:
Originally Posted by MrLinux View Post
Thanks guys... I still haven't done anything with this yet.... more symptoms...

on one sink, I have to run the water for 60 seconds before I get hot
water.

on one sink.... ( different time of day ) I have to run the water for 10
seconds before I get got water. I'm pretty sure that those are on different
water heaters... but I'm not 100% sure.

Both water heaters are identical models. They were installed at the same.
They are both Gas units. They are about 50 feet apart, installed in the
Attic. Both are about 5 years old... and both were turned off for over
a year. I don't know if they were drained or if they were full while
they were turned off.

The 'good' water heater is on the 'middle setting' and it's got good
hot water and starts giving hot water after 10 seconds or so. The 'bad'
water heater was on the 'middle setting +1' and it the water was hot...
but not that hot... not as hot as the 'good' one... I have moved it to
'middle setting +2' and it does provide hot water, but... it takes a
minute or so to get going....

I plan on turning off the 'bad' water heater and draining it. I'll be able to
figure out what systems are fed off of which water heater.

Before I cut any pipes and look at the dip tube... this is in my attic so it's
not real easy to work on.... is there an easy way to figure out if there
is a lot of sediment build up inside?

Thanks - jack
Maybe i'm confused, but doesn't a house usually have only one hot water system and one cold water system, regardless of how many heaters you have?

Whenever we've installed multiple heaters, its always cold in one, and hot out, then hot into the second and hot out to the house. I would think that
this should remain the same no matter where the heaters are in your house.

There's not really an easy way to check for sediment... you can hook a hose to your drain and try draining it, and if it's slow or no flow at all there's probably sediment (don't forget to turn off power first!!!)
The problem with this is that if there's sediment, you may have a hard time shutting it off due to sediment blocking the valve. Basically once you start draining it, you'll have to finish. I would load up on towels up there just in case.

You can use a compressor to help blow the water out of it, but you'll need to come up with some type of adapter. We made one at our shop that works quite well.
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Old 04-14-2008, 06:17 PM   #11
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Quote:
Originally Posted by Alan View Post
Whenever we've installed multiple heaters, its always cold in one, and hot out, then hot into the second and hot out to the house. I would think that
this should remain the same no matter where the heaters are in your house.

There's not really an easy way to check for sediment... you can hook a hose to your drain and try draining it, and if it's slow or no flow at all there's probably sediment (don't forget to turn off power first!!!)
The problem with this is that if there's sediment, you may have a hard time shutting it off due to sediment blocking the valve. Basically once you start draining it, you'll have to finish. I would load up on towels up there just in case.

You can use a compressor to help blow the water out of it, but you'll need to come up with some type of adapter. We made one at our shop that works quite well.
I've never seen it done but I've heard of using two water heaters at opposite ends of the house on seperate hot water loops to cut down on the time it takes to deliver hot water. Why they don't just use a re-circulating line is beyond me. This sounds like one of those systems though since they are so far apart.


As for not being able to shut it off that's why I mentioned having brass boiler drain caps handy. For $3 you have a failsafe should you not be able to shut it off.

You shouldn't need a compressor to blow water out of a heater. Gravity should take care of it. If it won't drain due to being full of sediment it's probably shot.
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Old 04-14-2008, 08:07 PM   #12
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Quote:
Originally Posted by Marlin View Post
I've never seen it done but I've heard of using two water heaters at opposite ends of the house on seperate hot water loops to cut down on the time it takes to deliver hot water. Why they don't just use a re-circulating line is beyond me. This sounds like one of those systems though since they are so far apart.


As for not being able to shut it off that's why I mentioned having brass boiler drain caps handy. For $3 you have a failsafe should you not be able to shut it off.

You shouldn't need a compressor to blow water out of a heater. Gravity should take care of it. If it won't drain due to being full of sediment it's probably shot.
We're plumbing a 5 bath house right now that they're talking about 2 different water heater locations simply because "There isn't enough room in one place for both of them" It is on a recirc system, but they're getting a huge tub for the master and the rest of them have 34" tub showers. vacation homes........

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