Low Pressure at Faucets After New Water Heater

If you had a water heater guy and a plumber say your installation was correct, I would have to say they don't know what their talking about. Sorry!

I would check the new stainless supply lines, if one of them is defective that could cause this problem.

breplum mentioned checking for problems with the water heater nipples.
They could be choking back the flow rate.

Address that, and also the softener.

And think big picture, any weak link in the looong chain can slow down the flow rate.

Ok, I tried bypassing the softener, but that made no difference. I get the same 70+ psi static pressure at the washing machine hot hose bib, but it drops to 10 psi when I turn on a hot faucet. If I try to run two hot faucets at the same time, there's almost no flow at all. Clearly a flow problem. I confirmed there is plenty of flow exiting the WH so it seems there must be a blockage in between there and whichever the first faucet in the circuit is (since every faucet in the house has low hot water flow). I tried to back flush the hot water line from the farthest faucet from the WH all the way back to the WH outlet, but that farthest faucet has an odd rectangular shaped end and aerator so I'm having trouble effectively blocking it to let the cold water flow into the hot side once any pressure starts to build up.

It would seem the next move is to try to figure out where the blockage might be, but I'm not sure how to do that. My house is 60 years old and the WH was relocated from inside to outside at some point before I bought the place. Some of the pipes were replaced at that point, but I'm not even sure how much of it was done. I'm starting to wonder if I'm going to end up re-piping the whole damn house to solve this.

Any advice on a next move would be greatly appreciated.

Maybe you screwed up the PRV when you rebuilt it.
Try just replacing it entirely.
Since both hot AND cold flow have been reduced.

Did you ever say if you have a whole house water filter?
If so, have you changed the filter?

We have had posters who did not even know they had one, until we prompted them to search.
It could be up in a drop ceiling, behind a furnace, whatever.

Check every plumbing control valve in the house.
Zone valves can collect minerals.
Old valves often need to be opened and closed three or four times, while water is flowing through them, to release trapped sediment or crud that is causing restriction.
This includes EVERY valve, like on both sides of the meter, water heater cold supply or hot outlet shutoff, all the water softener control valves.
Operate them all several times with water running through them.

Valves often get left partly closed after maintenance or repairs.
Re-check every valve.

How did you confirm there is plenty of flow exiting the water heater?

Have you ever addressed the possible issue of clogged or too tight heat trap nipples, which has been mentioned here several times?

Get another plumber in there, last guy might have been lazy, stupid, not familiar with old plumbing, or all the above.

Is there ANY valve or faucet where you open it and water comes gushing out like it should?
If so, please report on that.
Does the water heater drain valve give a good powerful gushing stream?

Is your plumbing copper or galvanized?
A mixture?

Galvanized might have become very narrow inside, and now sediment from heater swap is choking it somewhere.

ErikPiazza said:

Ok, I tried bypassing the softener, but that made no difference. I get the same 70+ psi static pressure at the washing machine hot hose bib, but it drops to 10 psi when I turn on a hot faucet. If I try to run two hot faucets at the same time, there's almost no flow at all. Clearly a flow problem. I confirmed there is plenty of flow exiting the WH so it seems there must be a blockage in between there and whichever the first faucet in the circuit is (since every faucet in the house has low hot water flow). I tried to back flush the hot water line from the farthest faucet from the WH all the way back to the WH outlet, but that farthest faucet has an odd rectangular shaped end and aerator so I'm having trouble effectively blocking it to let the cold water flow into the hot side once any pressure starts to build up.

It would seem the next move is to try to figure out where the blockage might be, but I'm not sure how to do that. My house is 60 years old and the WH was relocated from inside to outside at some point before I bought the place. Some of the pipes were replaced at that point, but I'm not even sure how much of it was done. I'm starting to wonder if I'm going to end up re-piping the whole damn house to solve this.

Any advice on a next move would be greatly appreciated.

Click to expand...

First off...stop wasting your time checking static pressures. The only thing that will effect static pressure is a closed valve or the elevation/height change of the gauge location.

So the pressure dropped all the way to 10 psi at the washing machine when you ran the hot water. Making progress!

How did you, ..."confirmed there is plenty of flow exiting the WH"??

Did you pull the nipples and remove any "heat trap" that may be there, as mentioned in post #5??

Do you have any shut off valves between the WH and the washing machine??

Did you check that all your cold water valves are in fact fully opened, the best you can tell??

Replace the PRV that you rebuilt as it sounds like it could be bad. Jeff and I were typing at the same time and had the same idea.

You can replace parts hoping to hit on the problem or you can do some flowing pressure testing and narrow it down.

OP...Please respond to all questions in Post #26. Thanks.

Can I suggest a really simple thing that may be the problem. Unscrew the shower head and aerators and see if there is crud in there. Any time plumbing work is done (in your case the water heater) crud inside the pipes can break loose and get lodged at the faucets blocking the water flow (especially if you have metal pipes).
A few weeks ago I did some work on the hot water line and suddenly I had at very small trickle of water hot or cold. I was confused how the cold water could have been affected by my working on the hot water lines until I remembered this and when I checked sure enough the shower head and aerators were totally clogged. Once I cleaned them out...Problem solved.

Good idea bartleyhs but I think he is having trouble with all the faucets.

It was ALL of mine too. Every fixture was totally clogged, okay I don't have a tub faucet which would be the only thing without a filter of some sort.
Does it really make sense to you guys that the cold water lines all of a sudden have this MAJOR issue after just working on the water heater?
I’m not a plumber, but I have run into this issue more than once. If he has galvanized pipes I would almost be willing to put money on it.
Anyway, wouldn’t it be worth a try, before a bunch of money is spent replacing things?

It can't hurt one bit to clean all the aerators out and see what happens

Diehard said:

You can replace parts hoping to hit on the problem or you can do some flowing pressure testing and narrow it down.

OP...Please respond to all questions in Post #26. Thanks.

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The guy said he rebuilt the PRV. Maybe,,,, something wasn't put together right or its just shot. Can the OP put a nipple and
union in between it and bypass it and see what happens.

As in replace the PRV with a nipple and union effectively bypassing it?
Sure I don't see why not.

So far, the only real progress we've made in this quest(assuming I'm understanding the OP correctly), is that when hot water is allowed to flow at the washing machine, the pressure dropped all the way down to 10 PSI.
If you couple that with his statement, "confirmed there is plenty of flow exiting the WH", that pretty much has narrows down an area of blockage. But of course that doesn't help us with the lack of flow on CW.

1) The cold water is flowing fine. It seemed reduced at first, but I've determined that's just the drop in pressure from 100 psi (with the faulty PRV) to 70 psi (after the PRV rebuild). I can run multiple cold faucets with no substantial drop in flow.
2) The hot water flows at approximately half the rate of the cold (takes nearly twice as long to fill a 1 gal bucket as the cold) and if I run 2 hot faucets, the flow from each reduces to a dribble.
3) I've cleared all of the aerators multiple times.
4) I have back-flushed the hot side several times from multiple places, opening and closing valves to no effect.
5) While flowing cold water into the hot side, the flow at ALL of the faucets appears normal, seemingly confirming that there is no blockage in between any of the faucets. That suggests the blockage is somewhere between the water heater and the locations I'm able to connect cold into hot (at the washing machine, and at the original water heater location).
6) I checked the flow from the water heater by connecting a hose to the WH outlet and turning the WH supply back on. Hot water flows normally.

Thanks for all the suggestions. I'm getting another plumber out here who can hopefully chase this down.

It has to be something with the water heater or the new hose. Might there be a defect inside the hose?

breplum said:

High pressure will not translate into flow if there is a blockage, so I am guessing somewhere at the WH is where the problem lies. Flow is dependent on friction or occlusion.
First off, pull the nipples and remove any "heat trap" that may be there.
Sometimes a floating ball in the dielectric nipples, sometimes a rubber flap assembly just at the tank threads.
If none of those items are present, then flow test out of the water heater into a bucket or hose to outside.

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after you have done what breplum has suggested, report back

I checked the flow of hot water coming OUT of the water heater and it appears fine, but I'll try one more time and remove the nipple to check for a heat trap.

ErikPiazza said:

I checked the flow of hot water coming OUT of the water heater and it appears fine, but I'll try one more time and remove the nipple to check for a heat trap.

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Did you visually check flow or did you put a gauge on the hot side of the water heater?
not the drain.

I suggest that you
1] turn off the water to the water heater
2] disconnect the hot at the water heater
3] disconnect the HOT supply line under a sink in the bathroom with low/no flow
4]. adapt a air fitting to the supply line
5] using a air compressor. blow the line out back to the water heater
6] repeat at the other bathroom with no/low flow