Water spike problems in my house.

[HeyBub]

Well, let's see....

Not true. Pressure builds until it reaches the pressure limit of the radiator cap, THEN it spills over to the expansion tank. Haven't you ever seen a radiator doing an "Old Faithful" or read the caution on a radiator cap?" In days of yore, there was no expansion tank and the coolant spilled onto the street.

PRVs do NOT allow water to back up into the city's mains. Water heater valves do NOT drip or flow at the first increase in pressure. It takes a substantial increase in pressure to trip a water heater relief valve, radiator cap, or PRV. And I do mean substantial.

It's not going to break. Pipes can handle a goodly amount of pressure.

The pressures involved in hot water (or even steam) are much less than the pressures exerted by freezing water. By a couple of orders of magnitude. Steam pipes are just regular pipes and none has ever been known to break from steam pressure. But they will break if exposed to freezing temperatures and not drained beforehand.

[kennybs]

Boy are you lucky I have some free time, are these the questions you have a hard time understanding?

"Hey Dumbo Your response is very refreshing--be so good as to explain just how a gage will resolve the problem. What does the pressure tell you if it's high? or if it's low? Or if it goes from high to low? What it does after or when a faucet is opened? In fact, if it's not bled properly you can't believe

anything it tells you other than steady state. In many cases you have to understand the problem before you can fix it."

1)What does the pressure tell you if it's high?

You have high pressure call a plumber. Then you can watch him turn the tank to pilot so it can't fire. Watch him relieve the pressure and put his gauge on. He will at that time tell you what the pressure is, he waits to see if it holds a constant static pressure. At that time he knows if the PRV is functioning or not. "Take note here it dosen't matter if the valve reacts in either 10 to 20 mili seconds it's the constant static pressure we're after.:) This will answer question #1 If the pressure is high the PRV is not functioning or is set wrong.

2)What does the pressure tell you if it's low?

If you have low pressure the PRV is working or the incomming pressure is low to begin with, but check with the plumber to make sure no ones brushing their teeth or taking a shower, will cover this later under usage ok. This should cover #2

3)Or if it goes from high to low?

Somebody flushed a toilet or their brushing their teeth again. I suggest you wait till they're done before you continue. That takes care of #3.

4) What it does after or when a faucet is opened?

Pay attention, this was already covered under #3

5)In fact, if it's not bled properly you can't believe anything it tells you other than steady state.

I actually don't understand what you mean here, but we're actually looking for the steady state your talking about. If you don't have it return to #1- 3.

6)In many cases you have to understand the problem before you can fix it."

Thats not what you said earlier, you said it was easier to replace things first, something about being cheaper in the long run, right.

O.K. lets continue before someone flushes again.

Now fire the water heater and watch the gauge, Note thermal expansion at work. Does it level off at incoming pressure ( PRV allowing for thermal expansion to push back into the main) or does it continue till the T&P leaks @150 lbs. because the PRV is making a closed system. If it's a closed system an expansion tank will be needed to keep the pressure down. Keep in mind at any time this little test could be stopped by opening a faucet, but be careful the increased pressure ( pressure spike I think you refered to it as) will be relieved at the faucet when opened.

Total Time to figure out the problem, 10 minutes, no guessing involved.

Your comments won't rile me, I have many friends who are engineers and I deal with people like you on a daily bases. They are by far the toughest people to work for/with, they have an answer for everything but usually lack commen sense. We're not talking aero space at Moog here, it's basic plumbing.Could many of us take it to your level, yes we could. But we choose not to because then we'd become just like you.

Maybe you should try staying at a Holiday Inn sometime, It works for us dumb plumbers.

kenny b

[MLD]

Thank you for you answers. I agree with everything you said (whether you care or not). A little dig here and there in reasonable but what's key is that you did it without getting too insulting and vulgar. That is appreciated and since I started down that path let me apologize. Obviously, I got carried away. But go back a bit--The original complaint was a high flow of water out of the faucet for about 10 sec. With no expansion tank in the system and no water coming out of the T&P valve, I told you what I thought, what your explanation? 10 sec. is a long time. One of your colleagues jumped into this--I intend to respond, if you're interested take a look. Your comment about engineers is not uncommon--lot of people have the same opinion. I've had the opportunity to be out in the field and deal with lots of different types--lab, factory, test, Military, flight line etc, both in and out of country. Fortunately, I've managed to get along and always got the cooperation that I needed. MLD

wrote in message news: [e-mail]...

[MLD]

Can't help but respond to your comments: Let's take them one at a time:

1. The car coolant: I said: ****As the coolant temp increases, volume increases, pressure increases until it gets to the radiator cap setting and then the coolant spills over to the expansion tank.*** You said:***Not true. Pressure builds until it reaches the pressure limit of the radiator cap, THEN it spills over to the expansion tank. One of us has a reading comprehension problem--I don't see any basic difference between the two comments.

1. You said:***PRVs do NOT allow water to back up into the city's mains. If you're a plumber, than get with it because that's not true. PRV's will let allow water back to the main. For your info, below I've pasted a manufactuer's description of his PRV. Note the comment on thermal expansion. So you don't miss it----under certain conditions it allows the expanding water to escape back into the supply main before it can affect the relief valve.-----

2. Pressures developed by expanding water. A car radiator cap is set for about 15 psi. T&P's I think somewhere between 100-150 psi, steam systems anywhere from 100-200 psi (only a guess). Expanding water in a closed system. Not too hard to come up with a pretty good number. Assume the water temp goes from 50 to 150F. The Specific Gravity (or density) changes about 1.87%. Use the following expression: Delta P=(delta V/V)*BM Delta P= change in pressure Delta V=change in volume V=trapped volume BM= Bulk Modules and for water=312,000psi So: Delta P= .0187*312,000=5834 psi If you think that the pressure required to trip a T&P valve was substantial, what do you think of 5800 psi? How will the typical household components (water heater, washing machine and hoses etc) deal with that level of pressure? That's why you have T&P valves on the water heater and because you don't want water spilling all over the floor all the time that's why expansion tanks are installed so as to absorb the volume changes without the accompanying rise in pressure. MLD

*******The use of a water pressure-reducing valve normally creates a closed system. When water is heated in a closed system, it expands, causing an increase in pressure. This pressure may increase to the set pressure of the relief valve (on the water heater) causing it to drip, thus releasing the expanding water and protecting the system against excessive pressure, This increase in the system pressure over that regulated by the reducing valve is called "thermal expansion pressure".

No. 25AUB by-pass Model water pressure reducing valves, are an economical solution of this annoyance, since under certain conditions it allows the expanding water to escape back into the supply main before it can affect the relief valve.

Effectiveness of the Thermal Expansion by-pass featureis limited to systems where the street main pressure is less than the setting of the heater relief valve. Therefore, the highest allowable pressure setting for the relief valve should be selected for widest effectiveness of a Thermal Expansion by-pass

temperatures

[kennybs]

"(whether you care or not)" Actually I do. Your previous statement speaks volumes and you need not apologize.

"You must be a very unusual plumber--I don't ever recall one that actually measured anything--typically, they replaced or cleaned out, nothing scientific or mind boggling."

I think your meeting the people who change the tires, not designing and building the engines.

"The original complaint was a high flow of water out of the faucet for about 10 sec."

Keep in mind your dealing with homeowners. Most of the time 10 seconds here is equivalent to 2ft of water in the basement and when you show up there's 2inches. We know waters not compressible so if the closed system had that much cushion of expansion the original problem most likely wouldn't have existed.

oh, and why the hell weren't you around last year, when I needed your help on superheated water.

have a good day, kenny b

[kennybs]

MLD,

O.K. I just read your latest post, your not an Engineer afterall.

kenny b

[MLD]

Game over, NE Patriots 35 Green Bay 0 --Yea! Now on to the Bears You had it right the first time, I am an engineer. Hard to explain what I did. Dealt with control and fuel systems. Didn't bother with steady state, only concerned when things were moving, at times one second was a long, long time. For example, in your car, step on the gas and watch the response of the tach--- basically an immediate reaction. A lot of what I did was in the time frame between the "step on the gas and the initial movement of the tach needle". Lots of things going on, throttle movement calling for more air flow, fuel pump increasing flow, mix the two and then into the cylinder, spark comes along, ignition and then engine speed increase--all done in maybe less 2-50 milliseconds. Didn't need gages since things happened too fast, used a lot of high response measuring devices. Oh, product was jet engines, primarily military fighter aircraft--F/A 18 and the F117 (stealth fighter). Got good enough at troubleshooting to be sent all over US and some other countries. Got involved in a lot of the "black box" analysis and some crash investigations. Because I had to work with a lot of different people at the field and test level it was imperative that I learn to get along with these guys in order to get their confidence and cooperation. Getting carried away. thanks for the positive responses. MLD

[DIMwit]

The public water system pressure in my area is always changing up and down several PSI day and night. I installed an new water heater a couple of years ago and found that an Xtrol type expansion tank for potable water was necessary to keep the water heater's pressure relief valve from popping every so often. I had tried another relief valve first, but the tank was necessary to absorb the pressure spikes. "Funny" thing is my water meter (in my basement) can be observed oscillating forwards and reverse if you look at the spinner dial on it top while you hear the meters chamber measuring the volume flow while this is happening. What is NOT so funny is that the actual dials on the meter seem not to go backwards (the 1/10 cu ft dial) when the spinner is in reverse. I don't think it adds up to any real dollar amount to my bill. But the frequent meter noise is annoying.

Funny how this thread came up as I was considering installing a check valve in the cold water feed to my hot water tank!

I will put one in for sure now.

Bob (another Bob)