Hi there!
Have had a problem with my hot water pressure for the past 6 - 8 months now. It started by being intermittent drop of hot water pressure to all taps in the house, while cold water pressure was perfect throughout. For a while, it would be such that I would open a hot water tap, let it run for 30 seconds, and all of a sudden the hot water pressure would magically kick in... but then after that working for a month or so, it didn't work any more, and hot water pressure was low all the time.
I did drain the hot water tank once, and that solved the problem -- but only for a while. Sure enough, the problem started up again, just as before, i.e. let tap run for a while & hot water pressure would kick in.
For the last 2 months, when it got really bad, I tried shutting off the cold water inlet into the tank, let some hot water run off from a nearby tap, then shut that tap again and opened the cold water inlet again. That seemed to jar something loose as cold water rushed into the tank and hot water pressure returned... but always just for a limited time.
Most recently -- i.e. in the last week -- that trick doesn't even work anymore. Have tried it a couple of times now, without success.
This is incredibly frustrating. I am not comfortable with soldering, etc. as this is a gas furnace (GSW John Wood), and that is just not my forte.
Any help you can provide with this would be greatly appreciated!

Thanks!
Jogger63

I think it is a piece of debri(small rock?) causing this, and may be in the water tank or up to where the hot water lines separate, since it is common to all.
Some good plumbers here may provide better/additional info.

Thanks Stratmando!
My trick yesterday actually worked again, but this time turning the cold water inlet into the tank off, opening a nearby tap to drain off some hot water and then (with that tap open) opening up the cold water inlet valve into the tank again. Seems to me that this is something that is in the tank... maybe a floater valve, or something of that sort?
Our house is only a little over 3 years old, and when I drained the tank a couple of months ago, there was no evidence of sediment...
We have hot water today, but clearly this will probably just be short term and doesn't address the bigger issue. So any further insight still appreciated on how we can make a permanent fix here...
Thanks!
Jogger 63

Did you ever get a fix for this? We have this exact problem, also with a GSW John Wood. (My apologies if you got a "Comment" from me already - I can't tell if it posted it or not... )

The problem could be in H / C nipples. Some nipples have built-in back flow preventers. They may be stucked in one position preventing free water flow. Also make sure cold water valve at the water heater is fully open. Check it out and let me know how it went. Back to you. Milo

Milo! I feel like you may be our saviour -and my hope for a hot shower. We have had the same trajectory as jogger63, and had come up with the same fixes. And, as with jogger63, now the fixes don't work. (We have been living with this intermittent problem for about 5 years!) The problem seems to often be triggered when the washing machine is going, or soon after.

So, I know the cold water valve at the WH is fully open. But the H/C nipples sounds hopeful. How do I
(a) find them
(b) unstick them if they are stuck in one position?

Thanks!

spike11

Hello Spike11...

Nipples are located on top of the water heater: one for incoming cold water and the other for outgoing hot water. If you have nipples with back flow device inside than they should be installed with arrows following the flow ( cold water: arrow points down / hot water: arrow point up )

Also, don't assume the valve above water heater is working properly. Sometimes you can close it just fine but when you open it back the interior part (yoke) gets stuck in half closed position.

Enclosing couple of photos of nipples for better visual. Back to you. Milo

Thanks for the quick reply, Milo! But we do not have nipples at the top of the tank. Just copper piping onto the connectors from the HWT. Is that possible? Is that right? Could that be our problem?

I could take a photo if that would help...

I was thinking about the possibility of internal nipples, but I don't think that's a possibility...

Well, just in case anyone else finds this post in the future, we solved the mystery. We have a gas-fired, direct vent GSW John Wood hot water tank. It is a 2005 model, installed in 2006. At that time, they had heat traps - not the nipple, but a plastic ball in a socket on both lines. This was somehow supposed to reduce heat loss - perhaps by "clogging closed" the line? In any event, they are cheap little plastic things, and they have a known issue of getting stuck closed (the cheap plastic ball sticks into the cheap plastic socket). This was particularly problematic if, during installation, the installer used heat to solder things closed near the top of the tank, contrary to instructions on the tank. Then, the plastic heat traps expanded and warped a little. Because they expanded, they have a tendency to get stuck. I learned all of this when the GSW John Wood warranty service guy (ours is long out of warranty, but he was recommended to fix our tank) came and told me this. Apparently, the tanks are no longer made with these heat traps. They now have "heat flaps". The fix was to cut the copper tubing and dig the cheap plastic heat traps out - they're actually sort of sunk into the pipes in the top of the tank.

Hope this helps someone!