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Old 03-03-2013, 07:55 PM   #1
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Low hot water pressure


A couple months ago we noticed steady decline in our water pressure, mainly our hot water pressure. This is most noticable on the second floor shower- it is difficult to have a quality shower on the third floor.

I borrowed a water pressure gauge and tested several places around the house. The upstairs (same floor as showers) laundry hot water line registers 44psi static pressure and 20psi with the hot water running. The nearby shower/tub has a flow rate of about 5.1 litres/minute (done by filling a 5gallon bucket) for the hot water and 11L/min for the cold!

I put the pressure gauge on the drain on the hot water tank and got a static pressure of 60psi and 44psi with the cold tap running and 25psi with the hot water running.

On an outside faucet I got 70psi static, and turning on hot it went down to 35psi. but turning it off it went back to 50psi and slowly climbed back up to 75psi.

I've flushed the hot water tank a few weeks ago and water coming out seemed clean and clear. I turned off the water valve to the tank to do this, so the water pressure was pretty low coming out.

Finally, I need to mention that last year the water main to my house was leaking- before my water meter (fortunately). The water authority dug it up and repaired it, but I can't help wonder if dirt got into my system.

Any ideas on how I can fix this or to further troubleshoot it?

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Old 03-03-2013, 08:02 PM   #2
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Low hot water pressure


Tell us a few things----how big is the main feed line---
do you have any gate valves in the system?

How old is the inside piping?

What is it made of?

Is the water heater shut off valve a gate valve or a ball valve?

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Old 03-03-2013, 08:51 PM   #3
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Low hot water pressure


I don't know about the main feed line. I suppose I could go look at the water meter at my front lawn, but if I recall it didn't look very wide. I think it is smaller than the 3/4" used inside my house. The pipes in the house are 3/4" copper and 3/4" cpvc pipe (I think).

The house itself is early 2000 build and I've owned the house for almost 5 years. The hot water tank was supposedly changed about a year before we bought it. It runs on natural gas.

I'm not sure if the valves are ball or gate. But the main shut off is has a lever control (I assume ball) and the hot water feed is has a knob (stop valve?). I'll try to attach pictures.


http://s13.postimage.org/77j26z1g7/plumb01.jpg
I hope this image helps.

Last edited by YoungRascal; 03-03-2013 at 09:05 PM. Reason: attached link for pictures
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Old 03-03-2013, 09:49 PM   #4
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Low hot water pressure


That's to modern a set up for the problem to be lime/rust clogged pipes-----

the shut off with a lever handle is a ball valve--those can be trusted---the screw type, gate valves sometimes break in a partially closed position---if this low perssure situation occured iediately after you worked that valve to service yourr water heater---there might me a cause--

There are several good plumbers on the site---I hope one or more adds something---I'm stumped.
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Old 03-03-2013, 11:29 PM   #5
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Low hot water pressure


Quote:
Originally Posted by YoungRascal View Post
Any ideas on how I can fix this or to further troubleshoot it?
Was there water pressure issues before you attempted to flush your tank?
Was the shower/tub you used to measure the hot/cold flow a single handle or two handle system?
Does the faucet in the bathroom with the low pressure shower show signs of low pressure as well? If you leave it off for a minute then turn it on, does it blast normal pressure before quickly dropping off? If so, does it do it on just hot? or both hot and cold?

Because of the pressure drop at the tank drain, I'm inclined to suggest the issue is before the tank, perhaps the gate valve. But if you are having a 50% pressure drop on a cold water hosebib when the hot water is turned on, then it suggests it's probably debris clogged in the PRV, or the PRV is shot (unlikely given it's age, but possible).
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Old 03-04-2013, 12:06 AM   #6
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Low hot water pressure


I'm thinking it's a fouled service line- before the heater
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Old 03-04-2013, 02:59 AM   #7
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Low hot water pressure


Thank you for your suggestions. I was hoping to find out if there was something obvious that I was missing. I don't have a lot of experience in plumbing (just basic stuff
like installing a shower, replacing fixtures), but do you think the next steps (e.g. to determine if it's a clogged service line or reducing valve) are simple?

>>the screw type, gate valves sometimes break in a partially closed position
Now that you mention it, this valve (H/W tank cold line) leaks a bit when I turn it, but is usally dry and in otherwise seemingly good order.

>>Was there water pressure issues before you attempted to flush your tank?
Yes, I had specifically drained the tank to address that issue.

>>Was the shower/tub you used to measure the hot/cold flow a single handle or two handle system?
One handle system.

>>Does the faucet in the bathroom with the low pressure shower show signs of low pressure as well?
Yes. It's visibly noticable. All taps on the top floor experience this the most, but it is evident on all hot water taps in the house.

>>If you leave it off for a minute then turn it on, does it blast normal pressure before quickly dropping off?
Yes, for about a second, then drops off. But "blast" wouldn't be the best description here for either hot or cold.

>>If so, does it do it on just hot? or both hot and cold?
Just the hot, I don't perceive any "blast then drop" with the cold.


I've never felt that the water pressure in the house was all that great but until now, it's never been enough problem to complain about. When watering my lawn in the summers, I
would notice that the neighbour's ocillating sprinkler seemed to spray water markedly higher than my sprinkler. I tried two or three different types/brands with no luck.
Thanks for you help! I appreciate your comments.
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Old 03-13-2013, 12:16 AM   #8
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Low hot water pressure


FYI, here's the update.

I pulled out the drywall to look at my prv. It's a Watts N35B (http://media.wattswater.com/1915088.pdf).

I cracked open the bottom plug and plulled out the strainer:
http://s4.postimage.org/m6bt5wc0d/IMG_0006.jpg

A quick clean and the pressure seems to be back to normal!
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Old 03-13-2013, 05:02 AM   #9
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Low hot water pressure


Good thing you found it-----that sure was a dumb thing to bury behind drywall---

Thanks for the update-----

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