View Full Version : No hot water pressure

11-19-2008, 07:41 PM
My house is only four years old so my water tank cant be more than 5yrs. A month ago I lost hot water pressure for a couple days and then the problem corrected itself. Winter just started here and after the first cold night I got the same problem. No hot water pressure through out the house, but the cold water is fine?

11-19-2008, 08:13 PM
I believe that your line leading either from the HW tank or to the HW tank is freezing. Once it warms up, the ice melts and pressure is restored.

You can test this theory by leaving the hot water dripping from one of the faucets on very cold nights. If the pressure remains good, then you have to figure out where the pipes are freezing and insulate them better.

11-19-2008, 09:46 PM
I don't believe you have a freezing problem because you didn't lose water pressure on the cold side and the thermal energy from the water heater would keep the cold and hot lines at the water heater free from freezing. Unless your water heater is at a remote location from your house exposed to the elements.

Let me ask if you have a water softening system attached to the hot side only. You could have an issue with it. The other possibility is the checks in the nipples of the water heater could be sticking. Some heaters have checks in the hot and cold nipples at the tank for thermal expansion. Good Luck and let me know how it goes.


Dan T1944
11-21-2008, 05:15 PM
I have the same problem, but all the time. Could Cal elaborate a bit on the terminology used in the reply regarding "checks in the nipples"? I am a novice , and don't know for sure what that means. I am in South Carolina and don't have any freezing problems. Thanks.

11-21-2008, 09:34 PM
The nipples attached to the hot water tank have little flaps in them that he is calling "checks." These flaps keep heat from escaping the tank, and thus saves you energy and money.

If you have no hot water pressure, and you live in a warm state, it's possible that these checks could be sticking. It's also possible that you may have a bad inlet or outlet valve, or that one or both of these valves in not open. You could have a plugged dip tube or a blockage in one of the flex copper lines that attach to the inlet and outlet of your tank.

I would start by opening and closing your inlet and outlet valves to the tank and make sure you leave them open. If you still don't have any hw pressure, you need to shut these valves and start removing the flex copper lines that attach to your tank, and look for a blockage.

PS: If you have an older tank with a lot of lime build-up, you could have an internal blockage in your tank, which might require that you replace the tank.

Dan T1944
11-23-2008, 07:49 AM
Eric, thanks, very helpful. I don't think it can be the outlet valve, as I have measured the pressure in the tank(at the drain valve). It is 50 psi with no faucets open, 0-5 psi with any one faucet in the house open. House is 3 years old, tank is in the attic. I have cycled the inlet valve, no change. The piping is CPVC up to the valve, copper from there. I have nearly worked up the nerve to cut the the CPVC, pull all the copper out and examine it.

11-23-2008, 12:04 PM
I would check the nipple at the inlet of the tank.

2 possibilities come to mind....

A ball type heat trap nipple that is jamming. Rip out the ball.

A galv. nipple that is clogged with rust. Replace with brass.

11-23-2008, 12:11 PM
Dan, I don't think the 50 psi you measured from the drain spigot means a whole lot, since there is probably 40 or more gallons of water in that tank pushing down into a small drain orifice. But even if you did have true city (or well) pressure at the drain, that would indicate that the inlet side (ball valve, dip tube, copper supply) were fine, and that the problem is in the outlet side.

Can't you unscrew the copper line from the outlet nipple? I don't think you need to start cutting cpvc at this time.

A picture of your setup would also be helpful.

11-23-2008, 01:19 PM
Pressure with no flow should be the same everywhere in the system (neglecting differences in height - it gets lower as you go up). If it is fine when there's no flow, and it drops radically when you open a valve, you have a flow/capacity problem, not a pressure one. As indicated, something is restricted, the inlet to the WH, or the outlet, or at the fixture involved.

11-23-2008, 03:08 PM
In this case losing pressure on the water heater drain indicates a look to the inlet side would be in order.

Dan T1944
11-24-2008, 02:01 PM
Jim is correct in that I mis-stated the problem. It is a flow problem, not a pressure problem. We have high water pressure in the neighborhood, so we have a pressure regulator on the incoming line (set at about 50 psi). I have checked it at an outside faucet, and it is 50, roughly the same as at the tank. I don't think the water height in the tank has much effect on pressure (4 ft. of water is only 1.75 psi.) I went to a plumbing store today and looked at a ball check valve. If the one I saw was typical, then I don't have them in my set-up. I can't unscrew the copper, as there is no union in the line, I have to cut it somewhere. I tried to post a photo, but don't know how to make it work. It is really standard, though. Just a ball valve and fittings. Thanks for all the suggestions.

11-24-2008, 02:39 PM
In this case losing pressure on the water heater drain indicates a look to the inlet side would be in order.

What if your were right but no one would listen?:D
Kinda like having a wife.

11-24-2008, 06:03 PM
In my case the wife I have now does listen...
The ex and her mother had the hearing problems...:cool:

Well 5 days has gone by with low flow...
Any takers on 5 more...

11-24-2008, 07:42 PM
What if your were right but no one would listen?:D
Kinda like having a wife.
It's just as easy to check both, the inlet and the outlet. But, if his pressure regulator is set to 50 psi, and he has 50 psi coming out of the drain, then how could there be a blockage at the inlet???

11-24-2008, 08:01 PM
I have measured the pressure in the tank(at the drain valve). It is 50 psi with no faucets open, 0-5 psi with any one faucet in the house open.

That would leave the inlet as being the problem.
BTW the original poster has left the building and is not coming back. t
The thread has been hijacked and that is who is being helped...

11-24-2008, 08:23 PM
You are exactly right, Redwood. :o

I misread his post. I thought he said the drain pressure was 50 psi, and the pressure at any faucet was 0-5 psi. So, it would definitely be the inlet that is restricted.

I wonder what did happen to the original poster? It would be nice to know if his pipes were freezing....

Dan T1944
12-03-2008, 05:39 AM
Sorry for hijacking the thread. I posted a question originally but got little response. At any rate, I have fixed the problem. On close examination, The Rheem heater did indeed have the "heat trap nipples"(pictures on Rheem's website, and available at Home Depot). Yesterday I cut the CPVC inlet line (it seemed obvious it was an inlet problem), removed the valve, nipple and associated copper piping. The ball in the heat trap nipple was jammed, as suggested. The workings in the nipple appeared to be damaged, probably from the original installation. I replaced the nipple with an open dielectric nipple, no heat trap. I chose high flow over efficiency. I installed a union, anticipating that Murphy's law would dictate a leak somewhere. Luckily, no leaks. The original nipple was incredibly difficult to remove. I had to heat it with a torch, and use an extender bar on my pipe wrench(again, luckily , nothing broke). I now have wonderful flow, 40psi with 3 faucets running. Thanks for all the suggestions, and I apologize if I broke protocol by hijacking the thread.

12-03-2008, 07:32 AM
Glad you got it fixed!
As for the Hijack at least someone benefited from the thread!:D

12-03-2008, 08:58 PM
Glad you solved your flow problem.

BTW, you did not hijack the thread and no protocol was breached.
You simply piggy-backed on to a similar problem, which happens all the time here.