Gate valve fix or replace?

[Michael Gabbay]

One of my 20 year old gate valves is starting to leak. It is the shutoff for a hose bib. I know it is the packing washer based on the leak. I could sweat a new ball valve on or remove the stem and replace the washer. What do you guys think? I'm guessing the washer is pretty standard. I'm not too sure how easy it will be to remove the stem though since it is 20 years old.

Mike

[Frank Chaffee]

Michael,
I would replace an old gate valve with a modern ball valve.
Frank

[Mark Rios]

Ditto what Frank said.

[Michael Gabbay]

I knew that was the answer. I just HATE plumbing! Oh well time to fire up the Mapp Gas. :D

Mike

[Frank Chaffee]

I hope that a real plumber will chime in with professional advice on soldering all types of valves to copper piping, as it would be invaluable to our Creeker archives.

I vaguely recall issues in screwing MPT’ed copper fittings into cast bronze valve bodies, whether plumber’s goop or Teflon tape was used.

When soldering cast bronze valves, I cannot remember exactly what amount of disassembly was required or how much protection was afforded by wet rag wrapping.

HELP,
Frank

This old blade needs sharpening.:o

[Larry Cooke]

I vaguely recall issues in screwing MPT'ed copper fittings into cast bronze valve bodies, whether plumber's goop or Teflon tape was used.Frank,

The company I work for sells a lot of plumbing related products, mostly industrial but plumbing none the less. One thing I have found to be true is that if you ask three different plumbers what's best for thread sealants, you'll most likely get three different answers. They generally use what works best for them, though there are specific applications where different sealants are used. For tapered pipe threads in a water application, teflon tape works very well if applied properly. The problem is that a lot of people don't know how to apply it and it can be much more time consuming than pipe dope, hence a lot of pros don't use it. The general rule of thumb is to start the tape two to three threads back (from the end) and wrap applying tension while doing so and I usually wrap it three to four times (no more than four) while spiraling the wrap back to towards the opposite end of the fitting again leaving about two threads. Hope this makes sense...

Every threaded connection (except compression and flared threads) in my house are sealed using teflon tape. To date, I have had no leaks at all. All of my compression and flared threads are dry, no sealants used, in fact using a sealant can actually cause leaks.


When soldering cast bronze valves, I cannot remember exactly what amount of disassembly was required or how much protection was afforded by wet rag wrapping.Soldering valves is a bit tricky, but not too hard once you've done it a couple times. The trick with valves is to first learn how to solder the copper pipe to end connectors first. This will give you a better idea of the metals color changes and when it's hot enough to apply the solder. Kind of like riding a bike, once you do it you'll be set. Now, if you're soldering a valve for the first time, I recommend that you disassemble it much as possible first. Take any and all packing out first. This way once you assemble it you'll know that you haven't melted any of the internal seals. Hint, be sure you have a union in line so you can do the final assembly. If you don't either add one or do the the following:

Most sweat-on (solder type) ball valves use teflon for the packing. Word of caution, not all do so I usually assume they aren't teflon. In any case once you're confident with soldering copper in general, using a very wet rag is acceptable. The pro's almost never disassemble prior to soldering because it's too slow. When doing a gate valve you always need to remove the stem packing nut and the packing. I would also remove the stem and gate as well prior to soldering.

Lastly, I do not like ball valves. Why? They almost always tend to leak, not externally, but rather past the ball and on down stream. They're great for quick on/off applications but personally I prefer to use a gate valve. When a gate valve leaks, usually you just replace the packing and you're good for a few more years. When a ball valve starts to leak you most likely will have to replace the ball valve. You can buy replacement parts for ball valves but most plumbing stores don't stock them so you just end up replacing it anyway. (That's my opinion on ball valves.)

Hope this helps.

Larry

[Ben Grunow]

As a builder I have watched the different plumbers we've hired and they all use different thread sealants. On method that I see regularly is to apply sealant (thin-just enough to color the threads), wrap the teflon tape as mentioned above, and then a generous layer of sealant. Tighten the fittings but not excessively. As hard as you can turn a pair of small wrenches (6" or 8" long) is OK. The sealants used range from Pro-dope, Blue blocker and mega lock. I think all of these are compatible with domestic water (good to check). I have rough piped 2 houses with this method with no leaks.

[Michael Gabbay]

Larry - If I replace the packing washer should I reseal the threads on the valve stem? If so would teflon tape be the right sealer?

Thanks, Mike

[Frank Chaffee]

Larry Cooke,
I thank you both for indulging me and contributing to the Creek archives from your knowledgeable position. Also, if my near future goes in the direction I have planned for it (which would be a first for me), I’ll be moved back to Catalina by year’s end and looking to meet up with you early in 2007.

Regarding Teflon tape, I have used this extensively, and most often in hydraulic oil piping. The majority of hydraulic oil system fittings are not reliant on the interference fit of tapered pipe threads, but either way, Teflon tape or pipe goop is a thread lubricant, and not a sealant.

I apply Teflon tape carefully from the beginning of the male thread, wrapping along the thread line and taking extreme care to not allow the tape to be exposed to the liquid or gaseous flow. I think I read once that Teflon is best kept away from pumps and filters.

Your advice to first-time and experienced solders’ alike is good; thanks.

…but I still need to question why you recommend a gate valve over a ball for on/off flow applications.

Again please note that I am just a guy with no tradesman plumbing training, but my conception of a gate valve is that it is best used for full on or full off applications (i.e. no throttling), and especially where material may be included in the flow and small amounts of leakage are acceptable when the valve is closed.

Ball valves, on the other hand, and in my experience provide clean opening and closing without the tendency to become obstructed by flowing debris or mineral build-up.

As I said earlier, these are the conceptions of ball and gate valves I arrived at with no input from pros and before I had access to the wonderful Creeker forum. To me certainly, and likely to some others, this thread is a good place to clarify some questions.

Thanks,
Frank

[Larry Cooke]

.but I still need to question why you recommend a gate valve over a ball for on/off flow applications. Ah, for flow that's a horse of a different color. First off, if flow is critical then you would be correct in using a ball valve. Since this thread was started for a home type of a repair, I assumed the application would be for normal household water use. Usually flow is not critical and but maintenance often is.

There are two types of ball valves basically, full port and standard port. (This is off the top of my head here but it's close enough for our purposes.) The standard port typically has a diameter that is less than the inside diameter of standard pipe - ANSI schedule 40 that is. A full port will have a port size the same or even slightly larger than said pipe. So, if flow is the issue then certainly you would want to use a full port ball valve since it has a larger and smoother interior. A gate valve on the other hand has lots of internal ridges and sometimes slight bends within.

As far as throttling (or controlling) the flow, a gate valve actually will give you more precise and consistent control but at the expense of more turbulence or restriction of flow when fully opened. Of course considering you might be trying to control the flow I'd say you're adding or creating more turbulence so it's going to be pretty much a wash except at full open positions.


Again please note that I am just a guy with no tradesman plumbing training, but my conception of a gate valve is that it is best used for full on or full off applications (i.e. no throttling), and especially where material may be included in the flow and small amounts of leakage are acceptable when the valve is closed.For material applications (depending on pressures) I would recommend a butterfly valve with the appropriate seat. Using most valves in a partially opened position is not desirable. You're subjecting the gate or ball to additional wear through erosion if you will.

Typically when a gate valve is fully closed the stem is protected from the liquid and pressures but once you open the gate valve the stem packing is subjected to the media and pressure. A ball valve on the other hand only sees the media during the opening and closing, once fully opened or closed its stem packing is shielded from the media.

I'm being overly technical here, I'm sure if you were to test these valves in a pulse test you'd find this to be 100% true, but the reality is the stem packing will most likely fail due to wear or corrosion. So...

Lastly, it's really not recommended to use a gate or ball valve for throttling purposes. There are in fact throttling valves but regardless, any valve used in a partially opened state for continuous use will wear the sealing mechanism faster than one that is either fully opened or closed.


Ball valves, on the other hand, and in my experience provide clean opening and closing without the tendency to become obstructed by flowing debris or mineral build-up.Given enough time they both will suffer from this. Granted, a ball valve is quicker to close so you're less likely to catch debris but over time it will and can happen to either type.

I have found through sales and first hand experience that gate valves tend to live longer in the real world. They're much easier to repair in place. Ball valves do offer quick on/off but at a higher cost due to having to remove them from the system in order to replace the seats. Consider this too, if your application requires quick on/off control then you're most likely going to be using the valve quite a bit more than a typical application. A typical application is usually where the valve is left on or off for long extended periods and only used for maintenance purposes.

Still awake? :)

Btw, looking forward to meeting you - though I do live and work a fair distance from Catalina. Of course it's a lot closer than Wisconsin!

Larry

[Frank Chaffee]

Larry,
Thanks for the thorough explanation.:)
Frank