Is it a water pressure or water heater problem?

[plumbbum]

Hi all-

Last week I roughed in a basement bathroom and plumbed in off the existing 3/4" pex with short 1/2" runs to the fixtures. I also extended the 3/4" runs up an abandoned HVAC duct to the second floor and capped them (this is for a future reno and I'd imagine that there's a considerable amount of air trapped in those lines). After doing that, my good lady wife notified me in the most undiplomatic way that she was only able to take a marginally lukewarm shower in our only functional main floor bathroom. I thought it was too coincidental that our 1 year old gas water heater would go on the fritz immediately after my plumbing work.

Here's what I know:
-I have a pressure regulator on my system that was adjusted to about 70psi.
-After my plumbing work, house-wide pressure dropped to 40psi
-I opened the pressure regulator all the way and pressure went up to about 48psi
-I then purged as much of the air out of the system as I could (again, I'd imagine that there's still air trapped in the line that goes to the second story) and seemed to gain another 3psi (51psi)

Now, when I turn on the hot water, the temp goes up to where it should be (~135 F) and then tapers down pretty quickly to about 100F, lukewarm.

What the heck is going on? What did I do wrong? Fix?

Thanks, all

 

[Reach4]

You are describing at least two problems. Bad water pressure, and the shower is not hot as measured at the shower. 4 questions come to mind...

1. Is there a mixing valve on the output of the WH that mixes in cold?
2. Does the water at the laundry also not stay hot? When the hot water goes cool, does the pipe coming out of the WH feel cooler also?

3. Does the outside hose bib pressure show 48 PSI when there is no water being used? If so, I suspect the PRV is bad or things have changed and you don't need a PRV now.
4. What is the water pressure on the hose bib nearest the PRV when you are drawing cold water into the tub?

If the pressure was low only when you are using water, I would look for a clogged screen on the PRV or a whole-house filter cartridge being clogged. But clogged screens and filters don't affect the pressure when no water is being used.

 

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[CountryBumkin]

Could you have "cross connected" (hot to cold) at one of the mixing valves?

 

[Jadnashua]

Any time you shut the water off and drain some lines, when you turn it back on again, it can dislodge some crud. That can clog up various things, many of them can be cleaned (like the aerators of faucets, or the showerhead). It does sound like your WH may be toast. Is the WH gas or electric? If you didn't shut the electric one off before your work, or didn't let all of the air out before you turned it back on again, you fried the element(s). IF they are not covered in water, and turn on, they'll quickly fail.

Air will be purged in the system once there is flow. The stubs that are capped, will likely eventually fill up with water as the air is absorbed in the passing water at their source.

 

[plumbbum]

Thanks a ton, Reach4. See below

You are describing at least two problems. Bad water pressure, and the shower is not hot as measured at the shower. 4 questions come to mind...

1. Is there a mixing valve on the output of the WH that mixes in cold?
Nope, there's no mixing valve .

2. Does the water at the laundry also not stay hot? When the hot water goes cool, does the pipe coming out of the WH feel cooler also?
The water goes cool at the tub, shower, kitchen sink and bathroom sink. I didn't check the laundry temp, but I think it also cools off. If not, I'll modify my response.

3. Does the outside hose bib pressure show 48 PSI when there is no water being used? If so, I suspect the PRV is bad or things have changed and you don't need a PRV now.
Correct, the outside bib shows 48 psi (actually 51(ish)) when all other fixtures are off. Yeah, under these conditions, it doesn't appear as though I need a PRV. But why the heck has the pressure go down so much and is it affecting the WH output? ...and can I get it back up?

4. What is the water pressure on the hose bib nearest the PRV when you are drawing cold water into the tub?
Cracky, the pressure at the bib closest to the PRV dropped to 35 psi when I turned the cold water on at the tub. The pressure at the bib farthest from the PRV dropped to 41(ish) psi.

I just removed the PRV and the water pressure at the bib, with no water being used, is still about 51 psi [unhappy face]. What gives?

If the pressure was low only when you are using water, I would look for a clogged screen on the PRV or a whole-house filter cartridge being clogged. But clogged screens and filters don't affect the pressure when no water is being used.

 

[plumbbum]

Thanks for the reply, Jim. All the supply line plumbing, including the house main coming off the city main are about one year old, so yeah, there could some crud in there, but I've got very new pipes. The WH is gas and there aren't any mixing valves on my system. ...any other ideas?

T

Any time you shut the water off and drain some lines, when you turn it back on again, it can dislodge some crud. That can clog up various things, many of them can be cleaned (like the aerators of faucets, or the showerhead). It does sound like your WH may be toast. Is the WH gas or electric? If you didn't shut the electric one off before your work, or didn't let all of the air out before you turned it back on again, you fried the element(s). IF they are not covered in water, and turn on, they'll quickly fail.

Air will be purged in the system once there is flow. The stubs that are capped, will likely eventually fill up with water as the air is absorbed in the passing water at their source.

 

[Reach4]

Correct, the outside bib shows 48 psi (actually 51(ish)) when all other fixtures are off. Yeah, under these conditions, it doesn't appear as though I need a PRV. But why the heck has the pressure go down so much and is it affecting the WH output? ...and can I get it back up?

4. What is the water pressure on the hose bib nearest the PRV when you are drawing cold water into the tub?
Cracky, the pressure at the bib closest to the PRV dropped to 35 psi when I turned the cold water on at the tub. The pressure at the bib farthest from the PRV dropped to 41(ish) psi.

I just removed the PRV and the water pressure at the bib, with no water being used, is still about 51 psi [unhappy face]. What gives?

Well, not needing a PRV is mostly good. You might ask the city water department if they changed things on a permanent basis. On the other hand it is bad in that you can't crank the pressure up to 75 to overcome water flow resistances.

If you map out the pipes like a schematic diagram, you can probably figure out where the resistances are. Clearly the pipe to the far bib split off before the pipe to the 35 psi bib did.

Note you can try the pressure gauge on the WH drain also.

The temperature problem may be a coincidence. If the dip tube of the WH broke, you can get hot initially but not for long. If the WH is electric, you could have a bad element; those usually have top and bottom elements that do not go on that the same time.

 

[plumbbum]

So, it's sounding like the water temperature and the low pressure may not be related at all. hmmm...

Could you have "cross connected" (hot to cold) at one of the mixing valves?

Well, not needing a PRV is mostly good. You might ask the city water department if they changed things on a permanent basis. On the other hand it is bad in that you can't crank the pressure up to 75 to overcome water flow resistances.

If you map out the pipes like a schematic diagram, you can probably figure out where the resistances are. Clearly the pipe to the far bib split off before the pipe to the 35 psi bib did.

Note you can try the pressure gauge on the WH drain also.

The temperature problem may be a coincidence. If the dip tube of the WH broke, you can get hot initially but not for long. If the WH is electric, you could have a bad element; those usually have top and bottom elements that do not go on that the same time.

 

[hj]

Did you install a tub or shower in the new room and if so what kind of valve/faucet did you use? You are describing what happens when someone uses a Delta mixer but does not install the cartridge. The "air in the capped risers" would have NOTHING to do with lowering the pressure and to a certain degree would help keep the higher pressure just like a holding tank.

 

[plumbbum]

Ho boy... I think you nailed it. I'm an idiot. I did install a Delta mixer for the shower without a cartridge. Doesn't sound like this will affect pressure in the system, but standby...

Did you install a tub or shower in the new room and if so what kind of valve/faucet did you use? You are describing what happens when someone uses a Delta mixer but does not install the cartridge. The "air in the capped risers" would have NOTHING to do with lowering the pressure and to a certain degree would help keep the higher pressure just like a holding tank.

 

[Jadnashua]

The instructions on the Delta rough-in say you must install the plug or the cartridge for the rest of the supplies to work properly without cross-connections. It's easy to miss. They used to come with that plug, but I don't think they do any more.

 

[plumbbum]

Hi Everyone,
So, yeah, I installed a Delta mixer without a cartridge. So, I bought a trim kit, installed the cartridge and ...voila!... my hot water problem went away. Thanks HJ.

But, that didn't explain the drop the in pressure. I've scratched my head a lot over that and here's what I think happened: Since the last time I checked the water pressure, the city of Portland moved their water transfer station from one block away from my house to 5.5 miles from my house. I think the pressure dropped when they did this, last December, and I didn't even notice the change in pressure until this other problem arose. So, the water pressure issue was a red herring, or at least a confounding variable.

Thanks a ton to everyone who helped.