Connecting old pool heater to new filter - copper to PVC transition

[rsaritzky]

Hi,

I inherited my Mom's house which has a 28,000 in-ground pool. I'm not sure I'm keeping it, so trying to keep costs to a minimum. I'm an experienced DIY'er with household plumbing - I've replaced the water heater at the house myself, for example. Anyway, it looks like the pool filter (30+ years old) needs replacing. The pool heater is again a 30+ year old Teledyne, with cast-iron "headers" with about 6 feet of 2" copper pipe leading to the old heater, which is all stainless steel. The backwash valve is also copper (brass? Can't tell through the discoloring.)

Anyway, of course all new pool filters use plastic pipe connectors. I've been told by a reputable pool service guy that the old heater gets quite hot, so a certain amount of copper pipe should be left on the existing heater before transitioning to plastic.

So the questions are:

1. How much copper should be left on the hot-water output side before transitioning to plastic?
2. Do the "compression" style copper-to-PVC adapters really work? For example, what if the copper is slightly out-of-round? OR
3. Is it better to sweat on a threaded copper connector and then use a threaded PVC coupler? I'm experienced in sweating copper pipe, so this is no problem except finding a 2" threaded copper fitting - not the typical home center type of size.
4. What type of plastic pipe is best? I assume Schedule 80 (grey) PVC is one option because of its increased strength over Schedule 40. Or is CPVC better?
5. Anyone in the Los Angeles area know of a supply house that sells to homeowners that has either (a) large copper fittings and/or (b) schedule 80 2" PVC pipe and fittings? I haven't tried Ferguson yet, which has many locations in the L.A. area - I assume they have the copper stuff, but not sure about the PVC.

Thanks

Ron

[CarlD]

The only part I can answer is to say you probably shouldn't use PVC with heated water. I'm not sure what temp causes PVC to have problems but when plumping a house, for example, PVC can only be used with cold water. For hot water you CAN use CPVC if it's available. It's rated for hot water and you can use it immediately out of any hot water heater. CPVC is significantly yellower than PVC.

The only problem I know of with CPVC is the transition to or from PVC--there are adapters.

AFAIK, while Sched 80 is definitely stronger than Sched 40, there's no useful advantage I know of to using it. I do have some Sched 80 ball valve quick connects but that was because I couldn't, at the time, find the Sched 40 ones. They work really, really well but were expensive.

For my solar panels, the only PVC in them is in the cold water feed to them. The heated water comes out of hoses and goes directly to returns.

[rsaritzky]

Hi,

Thanks for the reply. I'm not sure your reply makes sense, because as far as I can tell, all current-technology pool heaters use PVC pipe and connections. I've looked at a couple of friends pools with newer heaters. The ones I've seen use something called a "hi-temp union" to join the PVC to the heater itself - no "header" required.

As an example, I checked one current-technology pool heater, the Pentair Master-Temp. Its installation instructions say the following: "Two inch PVC water piping connects directly to the manifold/header on the heat exchanger using 2" PVC slip unions provided with the heater. The outer manifold remains cool; no heat sinks are required."

Plumbing references say that the maximum working temperature of standard schedule 40 PVC is 140 degrees. I know that even my 30-year-old Teledyne doesn't heat the water to anywhere near that close - 105 degrees max. However, the headers at the heater do get quite warm to the touch - not exactly sure how hot (gonna take out my infrared thermometer and power up the heater soon). But it seems like 18 inches or so of copper pipe leading away from the header should dissipate the heat from the heater, leaving only the heat from the heated water, which should as I said only be around 105 degrees. I can then solder a threaded coupler and use a high-temp union. According to some references I found, most hi-temp unions are made of Noryl plastic, which is stable up to boiling-water temperatures. So even if the copper pipe is 120 degrees, the hi-temp union can take it and transition to the PVC on the other side of the union.

I also know that schedule 80 PVC is stronger and so a threaded connector to, say a copper threaded coupler would be less susceptible to leaks over time. I have a schedule 40 threaded coupler connection from the pump to the current filter and it has cracked over time. A few extra bucks in stronger materials can go a long way in preserving the longevity of connections.

But all that being said, thanks for the reply. As of right now, I'm going to plan on doing the above - leave 18 inches of copper and add a threaded coupler and high-temp unions to go to the new PVC on the new filter.

Thanks again,

Ron