Sign of impending water heater failure?

I have a 40 gal natural gas water heater that's at least 17 years old and so is past its prime, but still heats up the water just fine and quite quickly, so there are no performance issues with it.
However, I've noted that over the past few years that whenever it fires to heat the water back up after hot water is drawn off for use that the water pressure in the house goes up significantly. I do have a one-way pressure reducer valve at the water service entrance that does not permit any back flow which was installed a few years ago, but the timing does not seem to correlate with the start of the increase in pressure after using hot water.
I do not have any expansion tank installed, but I know that when I originally moved into this house that this pressure increase was not present, so that's not the core issue.
Once I draw off some water from the pipes (a cup or two or water will bring the pressure back to normal) the pressure remains where it should. Is this increased pressure when water's been heated a sign that the heater's ready for replacement, or is the root issue somewhere else?
Thanks!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Scott Evans wrote:

Based on your description I'm wondering if maybe the thermostat setting has been changed in a direction to cause the water to heat to a higher temperature, or perhaps the heater's thermostat calibration has shifted a bit.
You didn't say where you are, but this being winter, maybe the incoming water is colder than it was a few months ago, which could cause a more noticable pressure rise, though you say this hasn't happened before.
If it was my place I'd install an expansion tank "just because." There are some tall skinny ones available that can fit in the space behind a heater which is located against a corner of the room.
HTH,
Jeff
--
Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Scott Evans wrote:

Has nothing to do with the heater or its (impending) failure.
You *must* have an expansion tank when a PRV is installed. The PRV might have a "bypass" port which has become clogged and that is causing the pressure build where there wasn't any initially.
The expansion tank will solve the problem AND give the heater longer life by holding the pressure inside the vessel to normal levels. Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
: Scott Evans wrote: : : > I have a 40 gal natural gas water heater that's at least 17 years old : > and so is past its prime, but still heats up the water just fine and : > quite quickly, so there are no performance issues with it. : > : > However, I've noted that over the past few years that whenever it fires : > to heat the water back up after hot water is drawn off for use that the : > water pressure in the house goes up significantly. I do have a one-way : > pressure reducer valve at the water service entrance that does not : > permit any back flow which was installed a few years ago, but the timing : > does not seem to correlate with the start of the increase in pressure : > after using hot water. : > : > I do not have any expansion tank installed, but I know that when I : > originally moved into this house that this pressure increase was not : > present, so that's not the core issue. : > : > Once I draw off some water from the pipes (a cup or two or water will : > bring the pressure back to normal) the pressure remains where it should. : > Is this increased pressure when water's been heated a sign that the : > heater's ready for replacement, or is the root issue somewhere else? : > : > Thanks! : > : : Has nothing to do with the heater or its (impending) failure. : : You *must* have an expansion tank when a PRV is installed. : The PRV might have a "bypass" port which has become : clogged and that is causing the pressure build where : there wasn't any initially. : : The expansion tank will solve the problem AND give the : heater longer life by holding the pressure inside the vessel : to normal levels. : Jim
I'd have to agree with that. The "change" could also be due to a loss of some of the air in the anti-hammer air traps, etc., especially if there has been any rearrangement in the plumbing at all. I can't recall what you call those air traps at the moment, but often they're enough to absorb the water expansion due to heat until they lose their air. An indicator of this would be that the pipes also bang or make thumping noises now that they didn't used to, or it's louder than it was.
Just my 2 cents.
Pop
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Generally agree also, even if you really don't have an expansion tank, the water did expand somewhere and that is what is not functioning. The expansion may have been incorporated into the WH tank design in which case it may be time to replace. If expansion was taken up in water hammer devices, maybe you need to recharge (in an older home, you may only need to drain the system and refill to allow air back into the traps).
Oatey makes a water hammer arrestor that screws onto a standard hose bib (like at the washing machine). If you have a hot water tap in this form, buy one at HD and screw it on, open the tap and see if that helps. Should have some anyway at the washer and dishwasher
17 Years is very long for a WH. Any replacement would certainly save you $ on your energy bills.
FYI the pressure reducer for the whole house only functions during a flow of water. It will not regulate static pressure. If you are concerned, check or replace the pressure relief valve on the WH. It is remotely possible that the check valve on this service entrance pressure reducer was malfunctioning originally and now just started working spontaniously thus removing the place for the water to expand (likewise for a check valve at the cold water inlet to the WH)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I had a similar change "for no reason" - but found that the reason was the 2 gallon tank for the reverse osmosis unit had been shut off.
Get the expansion tank.
Water expands when heated.
It doesn't need much, but it will force pressure up in order to get the increased space.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.