Hot Water Pressure and Valve Corrosion


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Old 10-22-07, 07:13 AM
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Hot Water Pressure and Valve Corrosion

Hi,

My heating system is oil-fueled. It also provides hot water for the house. A well supplies the water to the building. There are two issues regarding this system which I need help with:

First, the pressure of hot water is lower than the cold-water pressure. When a hot-water faucet is turned on, the water pressure is significantly lower than the water pressure coming out of the cold-water faucet. After about a minute or two, the hot-water pressure increases, but remains lower than the cold-water pressure, which is not so great anyway.

Second, the house is heated by hot water. The system is divided into three zones. One heats the lower level, which is partially below grade. The other two heat the upper level, with one covering the bedrooms, which are at opposite ends of the house, and the other covering the common areas (kitchen, living room, bathrooms, dining room, etc.). The heating level in the house is fine. The problem is that all of the valves on the heating side of the system show heavy corrosion and need to be replaced. The system is piped with copper.

Each zone has a shut-off valve about a foot past each circulator pump. In addition, because of the way the zones are set up, the two upper zones have shut-off valves where the zones branch to go to opposite ends of the house. In the three years we have had this house, we have never used these branch valves. Are they necessary, or can they be eliminated and replaced with copper pipe, as the shut-offs near the circulator pumps would remain?

Thanks in advance for any advice.
 
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Old 10-22-07, 12:19 PM
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Are you confusing flow with pressure? Does it take significantly longer to fill a glass to the same level with hot water than it does with cold water?

Being on a well you will NOT have constant pressure; the pressure will drop from the point where the well pump stops until it reaches the point where the well pump starts and then it will rise until the pump stops and the entire cycle will repeat as long as you are using water.

It sounds as if your domestic water is heated by means of a "tankless coil" contained within your boiler. Understand that this is a (relatively) cheap way to provide hot water and the results are rarely completely satisfactory. If you have a greatly diminished flow of hot water from your faucet compared to the cold water then the most likely culprit is scale deposits inside the tankless coil.

Is your well water considered hard? Do you have a water softener?
 
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Old 10-22-07, 01:14 PM
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Thanks, furd, for the reply. It takes significantly longer to fill a glass with hot water than it does with cold water. And, we do have "hard" water with no softening system attached. In fact, the well water is so bad that the dog will not drink it - he gets filtered water. As for the "tankless coil" system, is this something which is easily replaced or fixed? I like the fact that we are using the boiler all year round so as not to develop problems from non-use. Is there a way to augment the "tankless coil" outside of the boiler and still partially rely on the boiler year-round?
 
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Old 10-22-07, 01:44 PM
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Is there a way to augment the "tankless coil" outside of the boiler and still partially rely on the boiler year-round?
Yes, there is. It is called an "indirect water heater" and it is the best way to utilize the high efficiency of the boiler to heat domestic water.

It is not cheap but it WILL give you many long years of service. Some of the indirect heaters have stainless steel tanks, I believe.

The indirect water heater is piped to the boiler, using its own circulator, and it utilizes the hot boiler water via a tubular heat exchanger to heat the domestic water. You may need to add a new circulator controller.
 
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Old 10-22-07, 02:41 PM
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Thanks, furd. Your suggestion is the way to go. After your post, I looked into indirect water heaters and the concept seems simple. In your opinion, is this something that a reasonably-handy homeowner can do on his own? I've had problems with the reliability of heating contractors in my area
and would prefer to do as much of the work as possible myself.

By the way, do you have any comments on my valve problem?
 
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Old 10-22-07, 07:09 PM
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Can you post a few pictures of the corrosion? I would rather that you not eliminate the valves if they are able to isolate different parts of your system.
 
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Old 10-22-07, 07:47 PM
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Corrosion

With these valves being on the heating loops of the boiler, I would seriously doubt it had anything to do with the quality of the well water. Has the system ever had anti-freeze in it?
The most common cause of corrosion on the heat side is poor workmanship in not wiping off excess flux after soldering.
 
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Old 10-22-07, 08:51 PM
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I posted pictures of two of the valves. They are at:

http://s227.photobucket.com/albums/d...t=PA220038.jpg

I don't know if the system ever had anti-freeze in it, and there is no one to ask (bad divorce on part of prior owners - wife doesn't know and husband won't talk). The system is between 10 and 15 years old.
 
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Old 10-22-07, 09:34 PM
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That's nothing to be overly concerned about. Use a wire brush to remove the majority of the corruption and then tighten the packing nut about an eighth to a quarter of a turn. The packing nut is the hexagon portion closest to the handle where the stem comes through. Remember that the valve is upside down so you will be turning the wrench counter-clockwise when looking up at it.

I don't like to see screwed bonnet valves and I don't like to see gate valves installed upside down but there is no reason to remove them.

(If you don't know what that second paragraph is all about it's okay. )
 
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Old 10-23-07, 06:11 AM
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Thanks, furd. I don't like gate valves, period. If I have to, I will replace them with ball valves. However, I am still not sure what purpose any valves on the branch circuits serve, other than to give me the convenience of servicing one branch at a time. Because the temperature around here can get quite low, turning off a branch during the winter is not an option unless that branch is drained. Other than convenience, is there any other reason, practical or code, to have these valves?
 
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Old 10-23-07, 06:24 AM
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If you ever do have to service the system, when it comes time to purge the system after repairs, you will be thankful that those valves are there. They will allow you to direct the flow and only purge what you need to purge. The less you have to drain a system when servicing, the better.
 
 

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