Hot Water Pressure Problem / Oil Burner


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Old 12-23-12, 08:03 AM
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Hot Water Pressure Problem / Oil Burner

I'm not sure if I have a plumbing problem or a problem with my oil burner. Lately when running the hot water only at the kitchen sink, the pressure is fine at first. After the water has been on long enough for it to get fully hot, the pressure will drop and the pipe will start knocking. This also happens when I try to run the dish washer. It does not happen at other faucets in the house.

As I said, I have an oil burner and my wife's cousin, who is an HVAC guy says, based on what we've told him it sounds as if a certain (can't remember the term) coil is corroded and needs to be replaced but he hasn't looked at it yet. I'm not sure when he will be able to so I thought I'd ask here.

I don't understand why the pressure is good but goes south after it's been on for a bit. Any info is greatly appreciated. Thank you and Merry Christmas!!


Paul
 
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Old 12-23-12, 08:27 AM
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Hi Paul, Merry Christmas to you too!

First, let me ask this question:

You do NOT have a separate, stand alone, water heater?

You are sure that you get your domestic hot water from the coil in the boiler?

Lately when running the hot water only at the kitchen sink, the pressure is fine at first. After the water has been on long enough for it to get fully hot, the pressure will drop and the pipe will start knocking. This also happens when I try to run the dish washer. It does not happen at other faucets in the house.
Your description of the problem tells me it is something else. If you had a problem with that coil in the boiler, ALL of your hot water faucets would be affected similarly.

Does the pipe that feeds the kitchen faucet and dishwasher run separately from the pipe to the other fixtures? Is so, I would examine that pipe run...

Is your water piping copper? or is it galvanized?
 
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Old 12-23-12, 08:57 AM
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Greetings NJ Trooper,

No, I do not have a separate, stand alone water heater.

My hot water is heated thru my boiler.

Piping is copper.

The hot and cold lines run from the furnace and then above the basement sink and clothes washer and under the kitchen & bathrooms. From these 2 lines there are off chutes that then go up to each faucet and down to the washing machine, basement sink, etc.

Additional observation. A few minutes ago I ran the hot water in the basement sink just to make sure it didn't happen there. It did not but the water was not as hot as it usually is. The furnace kicked on and while it was running we ran the hot water at the kitchen sink and it did not lose pressure and knock. After the furnace shut off we tried again and as soon as the water got fully hot, it lost pressure and began knocking. At this point I tried the basement sink again and it was fine.

If it's a problem in the piping, why does it only happen after the water is fully hot? I would think it would happen all the time and why does it not happen when the furnace is running? Just thinking out loud here.

Oh, one more thing, when the pressure drops and the knocking starts, if we turn on the cold water the knocking stops.

I hope what I typed makes sense to you.

Thanks again for your replies.

Paul
 
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Old 12-23-12, 01:51 PM
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That's pretty strange Paul...

Is there a thermostatic mixing valve on the piping to the house fixtures?

If so, does the basement sink ALSO go through the mixing valve, or is it tapped off ahead (upstream) of it?

What are the settings on the three dials inside the aquastat on your boiler?

Would it be possible to take some pics with enough 'overlap' so we can see how the hot water is piping from the boiler to the home, and to the basement sink?
 
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Old 12-23-12, 02:36 PM
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Trooper,

Not sure about the thermostatic mixing valve but I'm thinking no. It looks to me as if the basement sink has water routed to it before it goes to the kitchen. I'll try and put together some pics. Thanks again.

Paul
 
 

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