Pex Manifold ?

[MountainDon]

... and makes it more difficult to get hot water to any faucet (because of that extra length pipe)(unless you insulate all your hot water lines).

Well, number one, there's nothing wrong with insulating all the lines, hot and cold. I've seen some upscale homes here that do that. Insulating cold prevents condensation and dripping. Insulating hot preserves the hot water.

The PEX tubing is not all that expensive when purchased in large rolls. At the very least if I was plumbing a new house I would install 2 small manifolds (H & C) so I could turn off the water to the showers and tubs from a distribution center. Showers are a PITA when it comes to working on them as in most homes you have to turn off the whole house. Ditto for the lines to the exterior hose bibs and the laundry machine supply faucets.

Also remember if you do a manifold system you do not need individual stops at each sink or toilet.

In most cases I don't think there will be much loss of extra heated water when using a manifold with separate lines to points of use. Some things like the kitchen sink and dishwasher are close enough together they should share the same hot supply line. But it won't make much difference to manifold or not, if after running the dishwasher the next hot water use is in the master bathroom. In many homes they are widely separated. That will of course vary from design to design.

Along that thought for some uses like the laundry it does not make any difference at all. At least our laundry machine senses the fact that the first inflow of water through the hot pipe is cold and it makes allowances for that.

[peteh2833]

Is there a connector to go from the PEX tubing to the line/fitting on the toliet and sinks??

[MountainDon]

You can use PEX to 1/2" FPT, then use the appropriate s/s braided flex hose to connect to the faucet or toilet.

Or here's a special connector, PEX direct to the fixture.



I believe the proper way to do that would be to run the PEX to a stub L and solder a fitting to that.



The copper stub would be secured firmly to the framing, cut to required length. They have a PEX end and a closed end so you can hook everything up and pressure test. Then cut off the end and complete with the appropriate connection fitting.

a side note: PEX should not be left exposed to direct sunlight.

[peteh2833]

Is it bad to run Pex  straight out of the wall and to the fixture and use the first connector? Pete

[MountainDon]

I don't really know pete. All I can say is the licensed plumber that did our re-pipe used the copper L's, under every sink and toilet and the city inspector loved his work.

In our cabin I'm not using the L's. I'm using the PEX. It's all under the sink, enclosed and even with the cabinet door open will never see direct sunlight as it faces the north wall. No inspections.

[NM_Shooter]

So keep in mind that the mechanics of the PEX are different from copper. 

I am going to paraphrase this, as it was related to me on the phone awhile ago.
With copper, you want to keep the flow rate lower, to not subject the pipe to erosion.  With PEX, you want to keep the flow rate higher (smaller diameter) as PEX accrues and grows some sort of fungal / mold substance if the water does not move.

Since you use smaller diameter to keep the flow rate up, this is pretty seriously affected by the number of fixtures that are on the tube...both pressure-wise as well temperature.  Using a manifold can help to reduce the effects of small diameter feed tubes. 

The manifolds can be fairly expensive, but why buy them when they are easy to make?

-f-

[peteh2833]

I found some on www.pexsupply.com that are inexpensive. I'm going to use the ones without the valves and just add my own ball valves and it ends up being $30 cheaper that way. The valves are 14.99 each and I need 8 ball valves for them. Pete

[glenn kangiser]

There are angle stops that go directly on the end of the pex and a curved bracket that nails right to the stud to support the angle stop and the pex.  The pex just bends and latches right into the nailed on bracket.

[cfabien]

I for one don't really buy into the "no fittings" being all that much of a benefit in terms of reliability. The only times I've experienced a leak in a pipe was when someone drilled or drove a nail into one doing an unrelated project. I am sure fitting failures do happen, but I would bet it is usually due to improper installation, either not properly glueing/soldering or not properly supporting the pipe. Plus, if you're going to use the copper elbows, then do you have hidden fittings anyway.

I do think there is some benefit to the manifold concept, the largest one being that it almost completely eliminates pressure fluctuations. So no more freezing or burning up in the shower when someone flushes a toilet or starts the dishwasher. Of course a properly designed trunkline plumbing system can perform well in this respect as well.

I think the biggest benefit to PEX is installation ease, just pull the pipe and terminate the ends. Being somewhat freeze tolerant is nice too, particularly in a building that may be unheated sometimes. Even with blowing out pipes, you can still get some water in them that can freeze.

[MountainDon]

You are correct in that the no fittings in the wall doesn't really matter much. It is primarily a labor saving benefit that comes along with PEX tubing in long (up to 1000 ft.) rolls. The exception to that would be when using PEX, as the fitting fits inside the tubing reducing the interior diameter. Copper and CPVC fittings, on the other hand, fit over the pipe. So with PEX try to keep the number of fittings to the minimum.

So no more freezing or burning up in the shower when someone flushes a toilet or starts the dishwasher.

Modern pressure temperature regulated shower and tub fixtures totally eliminate this problem. They are divine. I have retrofitted them. They work so well that if you slowly turn off the cold or hot supply line to the fixture the flow out the shower head (or tub fill) slows and stops at the same time the supply line valve is fully shut. Ditto on a toilet flush, dishwasher filling, etc.

[glenn kangiser]

Another advantage of PEX... many of the the copper lines in our area are dissolved to foil in a few years due to minerals in our water.