challenging pvc problem

[scrappy]

I'm going to build a 1000 gallon spa outside my slab-on-grade house. My original intent was to heat the spa with the 130,000 Btu/hr output high efficiency hot water heater augmented with solar panels on the roof. The "boiler room" is in the back corner of the house and my heating contractor/spa specialist POSER who didn't have a clue what he was doing placed a 4" pvc chase under the slab to the spa location 80' away with only a pair of Rehau Pex (only 13/16" inside diameter) to heat the spa. The slab is poured, the house is built. The spa is the last step before I'm finished. Once I excavate for the spa I'll yank the undersized Pex pair out and replace it with schedule 40.

But the largest suction/returns schedule 40 pipe I can fit inside the 4" chase is two 1/5" diameter pipes ' and they only fit if I use "repair couplings" aka "flush inside slip couplings" (they're the same outside diameter as the 1/5" schedule 40 pipes and made so they have 2 street ends or spigot ends [2 ways to say the same thing]. They reduce the ID of the pipe at the connection, so I'll lose some flow there, but as I'll only need 3 pairs of them to get to the boiler room and back, it shouldn't be too bad.
My big problem is this: I can't find any made as elbows. They're all straight. I've tried plastic oddities, spears, nibco, and midland and nobody knows where I might find 45 degree elbows made that way. It'll take 2 pairs of 1.5" 45 degree elbows to get thru the pair of 4" 45's that I created the sweeping elbow with that gets me from under the slab to above it in the boiler room.

The only solutions I've come up with are heat bending some sections to try creating the shape I need, then reaching them into the 4" pvc from above the slab and gluing them to some repair couplings that I'll have prepped on the ends of the 1.5" pipes that I've stuck thru from 65' away outside. It's either that, or I have to take out a section of 4.5" slab, cut off the 4" sweeping turn, poke the pair of 1/5" pipes thru, use conventional fittings to get back above the slab, then sleeve and bush them to protect them from being solidly poured in the slab. Does anybody have a better idea?

[TwinCitiesHotSpring]

I've read your post numerous times and I'm trying to visualize what you need...are you basically looking for elbows that will glue inside a 1.5" pipe? basically the link below is for pipe extenders..one side (smaller side obviously) glues into a 1.5" pipe and the other side connects to a standard 1.5" coupling/90/45/etc...are you looking for a 90 degree elbow with both sides that will glue into a 1.5" pipe"?

http://flexpvc.com/cart/agora.cgi?product=PVC-PipeRepair-Extenders

[Tman122]

What about flexible 1.5 inch water line instead of sch 40. Push it all the way through and use a barb to thread on the end and then a thread to PVC to get ya to the heater and the tub. No couplers or nothing it comes in 200' rolls if need be.

[vangoghsear]

What are the flow rates you want through the pipe?  What rate of rise do you want?  Is the spa water going to move directly through the piping or indirectly through a heat exchanger mounted out by the hot tub?  If it's indirectly through a heat exchanger, you can run hotter water and reduce flow rates making what you have installed possibly usable (I haven't calculated it yet, hence the 'possibly'), but you need multiple pumps to go indirectly.

[vangoghsear]

Did a couple minutes of research.  1" Pex tubing flowing 10 gpm loses about 5.5 psi/100' of run.  10 gpm with a 26 deg delta Temp can move 130,000 btuh.  You make the tub side a 20 gpm flow and that's +-13 deg DT.  Water in 104+13=117 deg F outlet temp max at shut off.

Requires two pumps, a heat side 10 gpm at total pressure of pipe losses, heat exchanger losses and heater losses; a tub side pump flows 20 gpm, with heat exchanger losses and whatever additional for filter, etc on the tub side.

http://www.valutechinc.com/swimmingpoolheaters1.htm

Check the specs for the heat exchangers in the link, right in line with what I was saying.  The 1" boiler side, 2" tub side, SS240 can handle 240000 btuh.