Either remove and replace all the old solder joints and address the ph level problem, or go with CPVC (Chlorinated Poly Vinyl Choride) You need a special glue (cement) for this type of pipe.

Thanks for the suggestion...but why CPVC...I thought that was only needed for hot water supply lines?

Nope CPVC is required for both hot and cold. the reason is the regular pvc can't withstand the normal house water pressure. CPVC uses a one step cement (glue) that doesn't require a primer. PVC is used mainly for drainage and requires a primer (catalyst) then the glue applied. I'm sorry you had problems with the flowguard. My guess you are in a Southern climate. I never liked it just for the fact that it seemed "flimsy" Read the chemicals on the label of the glue for the CPVC. Over time the chemicals may or may not "leach" into the potable water supply. I think your best best is to demo all the old flowguard pipe and install 3/4"-"K" copper for your incoming service. Then use 3/4"-"L" copper for all cold water lines. 3/4"-"M" copper for hot water lines. Tee off to each individual fixture with 3/4" x 3/4" x 1/2" Tees for pressure balance. Feed the 2nd and 3rd floor risers with 3/4" soft temper copper. This type of copper is easy to bend and feed up or down a chase and eliminates solder joints in the walls. I hope this advice has helped you some, and please post back and let me know how you made out. Happy holiday's to you and your loved ones, plumber Tom Edit message: I'm sorry I confused your post with somebody elses that had flowguard CPVC and had problems with the CPVC breaking and leaking. I was posting my comments to who I thought was that person, sorry for the mix-up. Hopefully that poster will read this. I live in Philadelphia, and could come out and give you a free estimate to try to help you resolve your problem. Check my credentials on bobvila.com and read my profile on www.kasamba.com

[This message has been edited by plumber Tom (edited December 11, 2003).]

How about cathodic protection using a sacrificial anode so that the annode is attacked (its made out of components that attract) instead of the joints.
Here in California we use annodes to protect against corrosive soils.
JWS

In california poly pipe is used for pressure pipe (schedule 40) up to (i think) 400 psi and then you use a thicker schedule pipe (schedule 80). I looked at a piece of pipe in my back yard and confirmed thickness and psi. Primer is used prior to glue but not required. Sanding is, also out here we use black pipe or ABS pipe for drain pipe and it uses a different glue.
JWS