Specific question about static pressure gauge reading and what it says about flow

[Robert33]

In the context of troubleshooting the cause of reduced hot water flow throughout the house after a new water heater installation, do equal hot/cold static pressure gauge readings, taken at faucets just a few feet away from the heater, constitute evidence that nothing about the heater or its installation could be the cause of reduced hot flow?

Thanks.

[LLigetfa]

Static pressure readings do nothing to ferret out flow restriction issues. Reduced flow could be from heat traps on the new HWT. Sediment can jam them up.

[jadnashua]

With no flow, connecting a fire hose and a straw, both would have the same pressure, but there would be a huge difference in their ability to flow once you turn their valves on.

[Robert33]

Thanks guys, it makes total sense to me but I wanted some experienced corroboration.

I've been having a three-way dialogue between a big box retailer from whom I bought the tank and who seems very interested in my satisfaction, and the plumbing company who installed it. The plumber came back out with a rep from the retailer and I foolishly failed to question the above "evidence" when I had the chance, needing time to ponder on it. Foolish should be capitalized considering that the test that was run just prior was to bypass the water heater by running the cold into the hot line which seemed to restore flow. I would have thought that test would be pretty conclusive but apparently I'm easily distracted by shiny objects (pressure gauge).

If I run the cold line into the hot again, myself, (and this time take precise fill measurements) to to try to eliminate the water heater as the cause, are there any gotchas I should look out for before trying it? Looks straightforward enough (shut off water, make connection, turn on water) but I did notice the plumber grabbing the pressure release valve at some point. Total noob here.

[LLigetfa]

When the plumbing is drained to install the HWT, sediment in the lines get disturbed when the water gets turned back on because of the sudden in-rush. This sediment then binds up one and/or the other heat trap, the result of which is reduced flow. This is not uncommon.



If you can get good flow out the draincock, then the heat trap on the hot outlet is the likely culprit. That is less common with a new HWT but more common with an old HWT where the system has been drained for other plumbing work. The sediment collects in the bottom of the HWT and gets churned up when the water is turned back on. This has happened to me more than once.

[jadnashua]

If there was a lot of crud in your supply lines, you may need to go to each faucet and fixture, remove the aerator and clean it out. Some devices have inlet filters...those could be partically clogged. Or, if they used tape on the joints rather than pipe dope, they may have been sloppy and left a tail, and that's restricting the flow. The heat traps could be installed backwards (upside down) or swapped (hot to cold)...they work essentially as one-way valves, and having one in backwards can severely restrict the flow.