Connecting PVC & CPVC to PEX & using check valves?

[Suceress]

I've had a thread up here for a long time about needing to remodel. The house was built sometime in the 1940s and there were some DIY modifications from previous owners. It's a single floor home raised off the ground with wood floor and about a 2' to 3' crawl space underneath.

The main issue right now is that we want to switch the laundry room with the guest bathroom. To do this, we have to take down a couple small non-load bearing walls, move some of the plumbing over, and run new electrical (fortunately the main circuit box is in this area).

The temperature doesn't usually get below freezing here, but the last few years we've had colder weather than usual and it got down in the 20s and caused some pipes to rupture. The exterior walls seem to be 2x6s with a thin layer of plywood on the outside covered in house wrap. On the inside is 1/8" thick wood paneling. There is no insulation (something I intend to rectify when I remodel).

Building codes have changed so I know that PVC is no longer allowed above ground for water supply. I was recently told that in the past few years the code changed to require a check valve for the washing machine water supply lines. I'm trying to find the right type and size to use. The current supply lines are 3/4" PVC (for cold) and 3/4" CPVC (for hot).

Specific changes:
I need to move the supply lines for the current lavatory over less than a foot to work as the washing machine supply lines. This will bring them closer to the exterior wall (and exposed part under the house) so I will need to wrap them in some sort of insulation-- something I could use advice on selecting as well as methods to keep the pipes warm in winter. They will be inside the room against a wall to avoid putting them inside an exterior wall.

I will move the toilet supply line over about 5' to the south and bring it up through the floor (again to avoid being inside an exterior wall). If it is possible, I would like to install a check valve on this so I can have a shattaf (handheld bidet sprayer) and I want to make sure there is no backflow.

The existing 3/4" supply lines for the washing machine would be moved inside the interior wall eastward a few feet to serve the shower/tub. The tub will be against the east and south exterior walls (with the longer side being on the east). I will have an access panel for the plumbing behind the tub inside the new laundry room.

The plumbing for the new lavatory is already somewhat in place (was roughed in for a utility sink) but will have to be moved slightly when the floor is redone so that the new vanity will sit forward away from the south wall about 3 or 4 inches. It is also 3/4" PVC and CPVC.

I already know what I want to do in terms of the DWV part, but I need to work on the specifics of the water supply. The lav and toilet will be against the south exterior wall, although there is a skirt that goes down to the ground, they are still vulnerable to cold in the winter (thus the existing lines are wrapped in foam).

My questions:
1. What is the best way to link 3/4" PVC & CPVC to PEX? (I do not have any of the crimping tools)
2. What is the best size PEX to use?
3. What is the best way to insulate the pipes under the house to keep them from freezing?
4. Where should I put the check valves (and can they be installed vertically?)
5. What kind of check valves should I use? (I've seen PVC & metal ones- solvent weld, threaded, & push-fit)
6. Any other suggestions?

Here is a sketch of the current layout (with fixtures removed) and how I plan to move stuff

Here is a sketch of a general idea of the future layout

 

[Reach4]

I was recently told that in the past few years the code changed to require a check valve for the washing machine water supply lines.

I have not heard that. That does not sound right.

1. What is the best way to link 3/4" PVC & CPVC to PEX? (I do not have any of the crimping tools)
2. What is the best size PEX to use?
3. What is the best way to insulate the pipes under the house to keep them from freezing?

There is different PEX. PEX-A is most resistant to damage from freezing. The tool for expansion fittings (usually used with PEX-A) is more expensive, with a manual tool costing maybe $170 for a cheap one. Professionals use a more expensive power tool. Clamp tools are cheaper. You can use PEX-A tubing with the cheaper clamp rings and cheaper fittings. The PEX-A is usually used with expansion fittings that meet spec F1960. The fittings cost more, but they have bigger ID.

1/2 inch is usually good for most things, but when a pipe carries water for several fixtures, then 3/4. A bigger house might use 1 inch or larger in places. I think for yours, 3/4 would be the biggest you would use, with most work in 1/2 inch. For hot water to a lavatory, 3/8 PEX is better, but it costs more than 1/2. The advantage is that it holds less cold water, so the hot can arrive sooner.

Use a corrugated metal connector to the 18 inches to and from the water heater.

In freezing, insulation can delay the water getting cold enough to freeze. In long term cold, you will want to run a small trickle of water through pipes that are in danger of freezing.

Actually, for insulation, I think you would be better off insulating the skirt at the edge rather than the pipes. That way heat through the floor could keep the area under the house from freezing. I don't know if that is practical for you.

4. Where should I put the check valves (and can they be installed vertically?)
5. What kind of check valves should I use? (I've seen PVC & metal ones- solvent weld, threaded, & push-fit)

I think you may have been hearing about air gaps on drain lines rather than check valves on supply lines.

I am not a plumber.

 

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[Suceress]

Thanks, Reach-4. The PEX that I was finding at big box stores looked to be PEX-B.
My water heater is rather far from where I am thinking of running PEX.
I've heard that sharkbite has some push-fit couplings and such. A friend of mine used those for his home. I was thinking that since I have 3/4" PVC that transitioning to 3/4" PEX would be ok (even if it is not necessary, I'd prefer to not restrict the flow more). I need to find the specs on actual OD and ID of PEX.

A plumber told me that 5 years ago, the code changed to require a check valve on the water supply lines for washing machines. I can understand why that would be a good idea-- if the water going in to the machine ever backs up, it could flow back and contaminate the water. I am still trying to find the code reference. Perhaps he was wrong.

For protecting the pipes from freezing, I was thinking that perhaps I could find some way to use those foil thermal blankets as curtains/skirting to keep some of the colder air out from under the house and keep the warmer air in. It's something I will have to look in to. I still need to have openings so that I can get under there to access pipes if anything happens.