Water pressure...do I have this right?

[TAHUSKER]

Been awhile since I have posted here, but everyone is always so helpful that I wanted to double check some things regarding home water pressure. Will try to make a long story as short as possible.

A neighbor said he had water pressure issues--the net of it was he ended up changing out his PRV and he still complains about low pressure. But he wanted to see what mine was for comparison. He had a gauge and we hooked it up to the hose bib outside and turned on that outside faucet--105 lbs. He said that's way too high (that I should be 50 - 70 psi) and that I'll have issues if I keep it that high. I figured my PRV may be bad too.

However . . . I went and bought my own gauge and did some reading. From what I think I understand, when we checked my pressure, we were reading static pressure--he just hooked up the gauge to the hose and turned it on--he did not have any other water flowing in the house. What I think the 50-70 psi refers to is the "dynamic" pressure when water is actually running from another faucet while the gauge is hooked up . . . is that correct?

I hooked my gauge up to the washer spigot and turned on the water--sure enough, it was 105 lbs. But when I turned on the faucet for the wash basin next to the washer . . . I was right at 55 lbs. So I think I am good to go and that my pressure and PRV are in fact just fine. Am I correct with that assessment? We have good pressure in the house from showers/faucets, but it by no means feels excessive. Appreciate any thoughts on it!

[Speedbump]

I'm not a Plumber, but 105 psi is too high. A PRV should hold the pressure at the set pressure no matter if another faucet is open or not. If you don't have a small bladder tank for the water heater, this could be a problem, or if you do have one and it's totally waterlogged, that could also be a problem.

[TAHUSKER]

I'm not a Plumber, but 105 psi is too high. A PRV should hold the pressure at the set pressure no matter if another faucet is open or not. If you don't have a small bladder tank for the water heater, this could be a problem, or if you do have one and it's totally waterlogged, that could also be a problem.

We do not have an expansion tank . . . our neighborhood is about 16 years old and they did not install them at that time. Maybe my issue is more that I should look to have an expansion tank installed first? Could the hot water heater be as much of the problem as a potential PRV issue?

[Nestor]

Tahusker:

Years ago they never installed expansion tanks. When water was heated in the hot water heater, the expansion of the water simply leaked backward through your water meter. Newer water meters have built in check valves to prevent that from happening because of the concern that a fire engine sucking water out of the supply piping could suck water out of your house and into the city water supply piping. If you're not having a problem with the P&T relief valve on your water heater spitting out water periodically, it's most likely because you have an older meter that's allowing backflow.

When it comes to water pressure, the ONLY thing you're concerned with is the static water pressure. That is, the pressure you read WITHOUT any other faucets in the house running. It could be that the reason your water pressure is 105 psi (which I agree is too high) is because of water expansion in your water heater. What you might want to do is connect your pressure gauge to your water heater drain valve, open that valve and then watch the meter reading to see if it goes gets that high when your water heater is heating water.

If you do decide to replace your PRV, a real good way to do it is to have ball valves both upstream and downstream of the PRV (for repairs and replacement) and a pressure gauge between the PRV and the downstream ball valve.

By arranging your piping that way, you can close the downstream ball valve and immediately tell from the pressure gauge what pressure the PRV is set to. If it's too low, you can adjust the PRV higher. If it's too high, you can release the water pressure downstream of the PRV and try again.

Also, you should be aware that in most cases you can buy overhaul kits for pressure reducing valves. If you know the make and model number of your PRV, any wholesaler that deals with that manufacturer will sell you an overhaul kit if you pay cash.

[TAHUSKER]

Thanks, guys . . . I really appreciate the feedback. I know next to nothing about plumbing--but I am trying to get more educated on it and become a little more self-sufficient.

I have never seen water come out of the relief valve on the water heater, so I am guessing maybe I do have a meter that is allowing backflow? I will do a test with the gauge as suggested on the heater and see what that results in. I did buy a new PRV last night just because I thought it needed to be replaced at the time--and it sounds like it does need to be swapped out. I think what I'll probably do is start there and just replace it regardless. Pretty sure that the one I have is the original, so I figure it's not a bad idea to just do it while I am thinking of it as it's bound to go eventually I would think.

Will have to look into a gauge in there as well--that's a great idea to have one installed, although I might need to get some practice on soldering before I am ready to go that route. I do already have the ball valve shutoffs above and below the PRV and meter (had a plumber install them just in case I needed to work on things and my old cheap valves were shot). I think I can just pretty easily swap out the PRV with the new one without any need to modify plumbing--so may just do that tonight.

[TAHUSKER]

OK, here's the latest . . .

I went ahead an installed the new PRV--figured it was probably the smart first move and I already had bought it. Went in pretty easily! No leaks (yet anyway)! I hooked up the pressure gauge to the same hose bib and turned on the water . . . no more 105 psi! Was reading right at 55 lbs.

Then I took the gauge back downstairs and hooked it up to the washer connector again and checked the pressure there. Same thing--was holding right around 55 lbs. When I turned the water on at the wash basin right next to it, though, the pressure was dropping down to about 25 lbs. Is that normal? Wondering if I will have to tweak things up a bit, but I guess we'll see with showers, etc tonight with the kids. Also need to run the sprinkler system tonight to see if I have any issues with the lower pressure.

I'm planning on monitoring the pressure when the water heater kicks on tonight while the kids are cleaning up. That should give me an indication of whether the water heater is causing some of the pressure issues as well.

**EDIT** I turned on the sprinkler system and the sprinklers were struggling to pop up all the way and weren't spraying nearly far enough. I adjusted the PRV to increase a bit and that seemed to do the trick on the sprinklers. PSI reading on the gauge after I shut them off is holding around 60 lbs still.

Also, I just checked the pressure gauge after the kids took showers . . . and it was back up to 105-110 psi. So it sounds like I also need to get an expansion tank added. I will see if I can take a look into that this weekend. Looks like something that a DIY'er might be able to do?? My father in law does some plumbing, so I think we can knock it out together.

[Nestor]

So, what's happening is that your new PRV (and probably your old one too) was sustaining the pressure at about 55 psi. But, the expansion of the water when heated in the tank would push that pressure up to 105 psi.

If you then release that pressure by opening a faucet while the water in the water heater is still hot, the pressure should drop down to 55 psi again and stay there.

The reason why you haven't seen any water come out of your hot water heater's P&T relief valve is because that valve is set to 250 PSI. You need to exceed 250 psi before that P&T relief valve will open.

PS: you don't need to know the rest:
The reason why a compressed air tank with 250 psi of pressure in it is so much more dangerous than a tank of water with 250 psi of pressure in it is because of water's inability to be compressed by pressure.

The math behind it goes like this:
Work = force X distance
multiplying through on the right side by area devided by area we get:
Work = (force/area) X (distance X area)
but, force divided by area is pressure and distance times area is volume, so
Work = pressure X volume
Setting P = pressure and V = volume the amount of work that could be done by a tank of air or water failing and the air or water going from one pressure and volume to a different pressure and volume would be:
W = PXD(V) + VXD(P)
or the work that could be done would be the pressure times the change in volume plus the volume times the change in pressure.
For both air and water, the second term calculates out to be the same since the volume is fixed and the change in pressure is equal for both air and water.
Where the big difference comes in is in the first term. The pressure times the change in volume for air is going to be large because the air will expand between initial and final conditions. For water, the change in volume from 250 psig to 0 psig is going to be negligible, so that first term will be very small for water. So, compressed air can do a lot more work than compressed water, and that's why standing next to an air compressor is potentially a lot more dangerous than standing next to a hot water heater.

[TAHUSKER]

Latest update . . . I added in an expansion tank the other night, so now I have my new PRV and an expansion tank on the system. I still need to test the pressure while the water heater is on. Will try to do that over the weekend. But I have to think that I should be good to go now with both of these changes.

Here's the handiwork . . . I'll probably catch a lot of grief for the Shark Bite connectors for the expansion tank. Swetting pipes is something that I just have not done yet--I plan to learn but I did not think this was the place to do so (I'm going to pick up some copper and the other materials and just start practicing in the garage to get a feel for it). The fittings were really easy to work with and it got the tank in place. I can always go back and swap them out for soldered connections. But they are in a very accessible/visible place so I can monitor for leaks--and the guys at the plumbing supply shop said for what I was doing they were a very good option for someone not comfortable with swetting. I'll report back on the pressure once I can test it out again.

[Nestor]

TAHusker:

Glad to see someone is wanting to learn to solder. In my view, the sooner you learn to solder, the fewer compression fittings you have in your house to replace.

Several points:

1. Don't buy any torch. Buy a torch that mixes the fuel with the air before igniting it. For example, this torch is made by a company called Turbotorch in Texas. It's called the STK-9 and it's very popular with plumbers because it draws air into the four holes in the brass base of the stainless steel mixing tube, thereby mixing air and fuel over the length of the stainless tube. The result is a very much hotter flame than you'd get if you didn't mix the fuel and air together first.



That mixing of air and fuel before burning is how a bunsen burner works. You want a HOT flame so that you can bring the fitting up to soldering temperatures rapidly so that nearby solder joints don't start to melt on you.

2. What does the flux actually do?

The single most important thing that flux does is prevent the oxygen in the air from getting at the bare copper metal. When copper metal reacts with the oxygen in the air, it forms an oxide film, and molten solder simply won't bond to that oxide film.

Copper rusts, but the oxide film it forms both adheres tenaciously to the underlying metal, and is highly impermeable to oxygen, and that's different from iron rust on both counts. So, as orange copper oxidizes (rusts), the brown oxide film that forms better and better protects the underlying copper from further rusting. This is why the copper piping in a house will typically outlast the house. The oxide film that forms becomes a more formidible barrier to oxygen in the air the thicker it gets.

Now, at room temperatures, the formation of that oxide film takes place fairly slowly. But, at soldering temperatures, that oxidation occurs almost instantaneously. So, we need a way to prevent the bare copper metal from oxidizing as you heat the joint up. Enter "flux".

Flux melts as the soldering temperatures are reached, and capillary pressure holds the flux in the joint. As long a there's flux in the joint, there won't be any air (or oxygen) in there. If you're ever getting concerned that you've been heating a joint for a long time, and the solder just doesn't seem to be melting, add more flux to the joint just to ensure it stays full of flux so that no air gets into that joint. At soldering temperatures, flux is a non-viscous liquid, and is easily pushed out of the joint as capillary pressure pulls the molten solder in.

Also, flux contains a chemical called zinc chloride. At soldering temperatures, zinc chloride acts like an acid, and it dissolves copper oxide much more aggressively than it dissolves copper. So, while it's always best to flux any pipes or fittings as soon as possible after sanding or brushing them, the zinc chloride will dissolve any copper oxide that forms on the brushed or sanded surfaces until they're fluxed.

3. The coupling you see below is called a "dimpled stop coupling".


Dimpling the coupling ensures that a pipe can only be inserted half way into the coupling, and that ensures that the coupling straddles the joint between two pipes equally on both sides. Otherwise, you'd have to mark the pipes and position the coupling carefully before soldering to be sure that the joint between the pipes was in the middle of the coupling.

The problem is that you OFTEN need to slide a coupling like this right over the pipe, and the dimple prevents that. SO, lots of people will tell you to take a small half round file and just file the dimple off on the inside, and that's the worst advice anyone can ever give you. That's because often these couplings are dimpled so deep, that when you file the dimple off on the inside, the wall thickness where the dimple is is negligible, or potentially even zero, so you'll have a potential leak through that dimple.

A far better way is to use a socket as an anvil and use a ball peen or regular hammer to hammer the dimple out of the coupling. That way, you're not reducing the wall thickness at the dimple.

4. Finally, there are several reasons for solder joints leaking, but the most frequently overlooked one is failing to allowing a path for air inside the piping to escape. When you heat up the piping to a soldering temperature of about 350 degrees Fahrenheit, the air inside that pipe is going to want to expand. Remember it's capillary pressure that sucks the molten solder into the joint. Capillary pressure isn't that strong to begin with, and if it's got to both push the molten flux out of the joint AND overcome a pressure inside the pipe, you're more likely to get a joint that's not completely full of solder.

So, whenever you start to solder a joint, ask yourself if you've provided a path for the expanding air to escape. If so, you'll have far fewer bad solder joints.

[pushkins]

While I like soldered joints I have to admit I have a huge liking of Shark Bite (Gator Bite) fittings, easy to use, have no record of failure, I've never seen one installed correctly leak (internal nylon sleeves must be used on plastic/pvc pipe), code compliant, and able to be in concealed locations (behind drywall etc...) One of the huge advantages is they can be fitted with water running (faulty shut off valves etc...).
Soldering is an art and good soldering is a profession albeit a slowly dieing one.