Problems with RO/DI connected to sink

[BeanAnimal]

I understand what you are saying, but don't see how it matters. The packings that are designed to "stop" the water, do so, and see the full pressure of the supply lines when closed. Any packings outby that, if wetted, may not see this pressure when the valve is closed. However, if they see no pressure, then they serve no purpose other than alignment or "backup". Adding pack pressure to these has no effect. The plumbing side can only push at it's static pressure, and therefore the "RO/DI side" can only push back at that pressure. The seat and other packings still only see the single pressure, not a combination of both. In other words if your supply is 50 PSI and it is pushing againt the stem, seat and other packings, this is no different than the "open air side" pushing back at 50 PSI. The net compression on the stem, seat and packings is a uniform 50 PSI. Please correct me if I am wrong. Some (very few designs) faucets may not do so well with a high pressure pushing back against empty supply plumbing, and valve damage could occur (but is not likely)... but the pressure diferential would need to be pretty large and most water supplies don't fluctuate in pressure that much. In most cases the valve would "leak into the supply piping" and work correctly when line pressure was restored.

A "laundry valve" and a stem type faucet are not all that different. The stem type faucet is made to fully open in a turn or less and has more "wear parts" in it for alignment and ease of turning. Take a look at a 1/4 turn "frost free" hose bib sometome. It is made exactly like a typical stem type of faucet. Older faucets are very similar to the "laundry valves" listed above and are either gate or globe type, some may be a multi turn seat or needle. In none of these cases will back pressure be a problem. The closing force is applied by a level or screw. Any "backup" springs are much stiffer than the typical working pressure.

Bean

 

[jdieck]

Not all faucets are designed the same but the above diagram may help me explain why some have a higher tendency to leak.
In the diagram the left side is subject to the tap pressure and the right side is connected to the spout which under normal circumstances for a sink is open to the air. When the valve is closed, the disc at the base of the stem shuts off the feed from the left side (the high pressure side) and as such the packing on the bonnet and the stem are just open to atmosphere via the spout. When the faucet is open and water is flowing the pressure in the right side is still lower than the tap pressure and will be equal to just the back pressure created by the friction, fittings or diameter restrictions at the end of the spout. For this reason under normal circumstances the packing of the bonnet and stem although they see some pressure do not see the full tap pressure unless you plug the spout when the faucet is open. That plug could be a solenoid valve from a washing machine or an RO/DI unit as their flow is so small that is equivalent to basically plugging the spout.

No in faucets and valves as the one in the diagram (which are very similar to the ones for the laundry or garden) the bonnet packing as well as the stem packing (which is usually conical) can be tightened by tightening either the bonnet or the stem packing nut thus being able to stand higher pressure and if the packing is not damaged but leaks the only thing to do is tighten the nuts and the conical or flat packing will be tighter.
Many sink faucets, specially the fancy ones have a lot more parts and many of their packings specially the ones at the bonnet body and some on the stem consist of simple O rings seated in a grove and the seal is made by the O ring by deforming it when sliding one part into the other so the O ring presses against the face of one of the surfaces and the grove sides. This kind of seal can not be made tighter than originally designed for and are the ones with higher probability for leakage.

By the way you are right, back pressure can not be higher than the pressure of the tap but without restriction the pressure downstream from the disk is much lower than the tap pressure and that is what the stem and bonnet packing see, a lower pressure which will rise up to the tap pressure when the spout is restricted.

By the way a worn packing in the stem, bonnet or spout body that may not leak under normal unrestricted spout circumstances will certainly leak when subject to full tap pressure.

I hope this helps to clarify the point.

 

[BeanAnimal]

I am very aware of how most types of valves are constructed, and am not sure what that post is trying to illustrate. The picture above shows a typical globe valve that you would find on the outside of your house or your laundry area conenctions.

The direction of flow is such that DISC seals the stem and packing area to an extent. You are correct in the fact that during "open ended" operation that the packing sees no pressure. When nothing is hooked to the end of the valve, the disc seals the orifice and stops the flow, leaving the seat and packing at atmoshphereic pressure. However, the packing and stem are designed in such a way that they form a seal when back pressure is present of flow is reversed. The reason for this design is to protect the disc from erosion and deposits. You may wish to know that in high temperature or high pressure applications, the flow is reversed in a globe valve. The idea is to allow the pressure to press the disc against the seat and accomodate any thermal expansion of the seal. In this scenerio the packing does see the pressure, but the disc actually has a better chance of forming a seal. In most cases the packing can be sealed with a slight turn of the packing nut.

I have played with and rebuilt dozens of different valves, from hydraulic spool valves, to your basic "garden hose spigot" globes.

I am usually right on the same page with you jdieck, and agree that your explanation above does apply to a globe valve, but again it makes no difference with regards to the proper function....

Bean

 

[BeanAnimal]

doh.. i responded to the picture, but there was no text... by the time I posted the text appeared.... your sneaky!
In any case...

 

[BeanAnimal]

Thanks for taking the time to try and explain your point.... it appears that we are on the same page... I do agree that a worn stem or packing may not leak until it sees back pressure, esp in a globe type design.

I guess my I should have qualified my statements as to being only relevant to a properly functionong valve with all parts in good condition. I should have also said "If the vale is in proper working order, then the back pressure should have no effect on it's proper function"

 

[RobbyG]

I am not even sure what transpired here I saw a pretty picture, a few posts in a foreign language and I understood nothing. Does anybody have a Fluid Dynamics to English Translator I can borrow? BTW I agree with the guy on the Left

Nahh just kidding, but that was deep.
What I am not sure of is how is this different from when someone opens a pipe in the room below or above the same faucet. Seems like the same changes in pressure would occur?
If im wrong let me stick with my first paragraph :

 

[smleee]

Let me give it a try. You have your sink faucet off, so all the pressure is built up behind the valve (the faucet handle) you use to turn on/off the water. There are maybe 1 or 2 more o-rings/equipment after the valve which never really get any pressure since they are dry when the water is off and when the water is on the pieces don't have much pressure on them since the water is flowing. But put on an RO unit and those 1 or 2 pieces will see a great deal of pressure. Yes? That's how I understand it.

eee

 

[jdieck]

<a href=showthread.php?s=&postid=6945288#post6945288 target=_blank>Originally posted</a> by RobbyG
...What I am not sure of is how is this different from when someone opens a pipe in the room below or above the same faucet. Seems like the same changes in pressure would occur?

Yes they occur, specially when you are upstairs taking a shower and someone flushes the toilet downstairs....
Well it is a bit different but my reaction to it will be quiet the same.

I would yell @#$% ! :lol:

 

[jdieck]

<a href=showthread.php?s=&postid=6941154#post6941154 target=_blank>Originally posted</a> by BeanAnimal
doh.. i responded to the picture, but there was no text... by the time I posted the text appeared.... your sneaky!
In any case...

:lol: Sorry, I was testing the link before writting up the post.

 

[RobbyG]

OK Smleee and jdieck you have both now officialy confused me.

Smleee you kind of got a bit Vague at this part
"But put on an RO unit and those 1 or 2 pieces will see a great deal of pressure. Yes? "
So why do they see more pressure? I understand that the seal see's no pressure on one side but how does.... ahhh forget it, someone break this down for me.

jdieck im not sure if your joking or serious, but my head is hurting after reading your first post, are you really saying it's the same, if so how does the RO really add to the problem? since this kind of thing is happening all day with all the pipes.

 

[BeanAnimal]

If ythe seals in your faucet are old or bad, the RO unit (or any other device hooked to the faucet) put pressure on a different set of seals (in laymens terms). These seals may fail (or have already failed) and leak water. You never knew they were bad because they never had any pressure against them.

Bean

 

[jdieck]

<a href=showthread.php?s=&postid=6948032#post6948032 target=_blank>Originally posted</a> by RobbyG

jdieck im not sure if your joking or serious, but my head is hurting after reading your first post, are you really saying it's the same, if so how does the RO really add to the problem? since this kind of thing is happening all day with all the pipes.

My friend, I am more serious than a hearth attack :lol:

Bean... You are putting it to easy! let me try to really mess him up.

Robby... Have you ever tried to stop the flow out of a hose with your thumb? Why do you feel more push the more you want to stop it?
Because you are building pressure inside the hose.

Let me try an analogy. I have a garden hose connected to a faucet and the hose is connected to a soaker that I use to water our veggies, yes one of those that has a little plastic valve to close the soaker without you having to walk all the way back to the faucet when you want to change the location of the soaker. Now it just happens that the hose connection to the faucet is not tight enough or the packing is not that good (yes one of those hard thingies difficult to make them seal... yes yes pliers will do but my wify will complain if she can not disconnect the hose when I am gone).
In any case, if the soaker valve is open when I open the faucet the hose connection may not leak or leak a little bit, this is the case when the sink faucet is open and no RO/DI unit.
If I close the soaker (Case RO/DI installed) the hose will straighten up and turn a bit rigid due to the pressure build up and the connection to the faucet will start leaking all over.

Now imagine the garden faucet is the disk that closes the flow in a globe valve, the packing between the hose and the garden faucet is the packing on the globe valve stem and the hose is the spout.
Get it now?

 

[brucoh]

BTW guys, original poster here. Maintenance came in and fixed my faucet today, no questions asked. I'm going to be out of town for a couple of days, but when I get back, I'll try to rehook everything up and see how it goes.

 

[jdieck]

<a href=showthread.php?s=&postid=6949407#post6949407 target=_blank>Originally posted</a> by brucoh
BTW guys, original poster here. Maintenance came in and fixed my faucet today, no questions asked. I'm going to be out of town for a couple of days, but when I get back, I'll try to rehook everything up and see how it goes.

And you will leave us in suspense as to what did he find? Thats unfair!

 

[smleee]

<a href=showthread.php?s=&postid=6949955#post6949955 target=_blank>Originally posted</a> by jdieck
And you will leave us in suspense as to what did he find? Thats unfair!

:lol: ttt

eee

 

[RobbyG]

I understand now, it makes sense, haallaa lullya. My eyes have been open and blasted with the sacred water (Ahh I hope thats water you blasted me with ) Thanks. Good education lesson.

<a href=showthread.php?s=&postid=6948967#post6948967 target=_blank>Originally posted</a> by jdieck
My friend, I am more serious than a hearth attack :lol:

Bean... You are putting it to easy! let me try to really mess him up.

Robby... Have you ever tried to stop the flow out of a hose with your thumb? Why do you feel more push the more you want to stop it?
Because you are building pressure inside the hose.

Let me try an analogy. Get it now?

 

[jdieck]

:thumbsup:

 

[trmiv]

Sooooo, given all this talk, what is a good way to hook up an RO/DI unit for us apartment dwellers? The washer supply? Is that Y fitting available anywhere, or is that something I'd need to get online at place that sells RO/DI stuff?

 

[jdieck]

Look for the Y connection (the metal ones) at your local hardware store in the garden section were the hoses and sprinklers are.

 

[Emmelemmo]

Its not a matter of more pressure but pressure where the faucet is not made to have pressure. The faucet is made to hold pressure behind the seals at the on/ off point. The RO/DI unit can create similar pressure past the shut off point where seals are constructed to only prevent water from leaking at normal flow not at pipe pressure. So it is simply pressurized water in an area not built to hold pressure. The reason that you don't see such leaks on a washer setup is that there are no seals after the water cut-off like you have in a sink faucet.