Tankless Water Heater Plumbing Question


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Old 08-02-17, 03:57 PM
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Tankless Water Heater Plumbing Question

Recent installation of a tankless water heater. I'm wondering if the hot and cold lines are restricting flow into and out of the unit due to the "U shaped" bends.
Please see pictures below. First one is the hot side and second is the cold side (with the gas line directly in front). Should these lines be a straighter flow into the unit or does it not matter that they're basically doing a 180 degree turn so close to the tankless water heater?

Thanks in advance.


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Old 08-02-17, 04:06 PM
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If a ~60 psi is maintained, there shouldn't be a problem.
 
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Old 08-02-17, 06:15 PM
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What's the best way to check the pressure now that everything is installed? Can you just screw on a pressure gauge to the screw-on bypass on the inlet side (cold) of the water heater valve?

Just FYI, it's a Rinnai RUC98I if it matters.

Thanks again.
 
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Old 08-02-17, 07:01 PM
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You can connect a pressure gauge to the hose bib.
 
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Old 08-02-17, 08:07 PM
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The piping is fine.

That hose bib attachment is for draing purposes and sometimes they are a 3 wat valve. So you will not neccesarily get a pressure reading from there. But I cant see..

What are your issues?

If a new install often the inlet screen gets clogged. You need to turn the water off and open the union to see the screen.

Additionally there is a built in flow restrictor in tankless units. It will slow the water down to get hotter temps. But sacrificing GPM.

Whats the temperature setting set at?
Did you adjust all your scald protectors at the showers?

Explain what your issues are.
 
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Old 08-02-17, 08:11 PM
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Also looks like 3/4 gas line to unit. cant tell.

But looks like they may have used a 1/2 " flex line. Thats a no no if so. Read the tag on the flex line. They can only flow so much gas for the ft of the flex line. So you may have a 200k btu unit but the flex line can only flow say 100 k btu.

Just a thought and talking out loud.
 
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Old 08-02-17, 08:24 PM
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I did the install myself so I just wanted to check my work. Could be imagination but there are times when I feel the pressure decreased.

Gas flex line and pipe is all 3/4. Temp is set at 120 degrees. Just checked the flow screen today, which was perfectly clean.

I liked the idea of at least testing the pressure. Good point about gas pressure too. Can that be tested by placing a gauge at the end of the flex pipe after disconnecting from the water heater?

I attached a better picture of the isolation valves. Will it work if I just put a pressure gauge on the cold side bib with the bib's ball valve open?Name:  9D9BE81B-34EC-48FE-BF90-ADC054F138FF-429-000000BE34C92781.jpg
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Old 08-02-17, 08:35 PM
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Yes if those are the valves then do as you say.

The gas pressure gets tested with a manometer. I doubt you have a gas issue.. The manometer gets attached where the drip tee cap is.
 
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Old 08-24-17, 02:08 AM
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You can check the pressure anywhere in the house -- it'l all be the same, except for some minor loss if you go uphill. I think it's .41 pounds/ft. You would also pick that up going downhill.
 
 

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