It is possible that there is an "inline eductor" in the mixer. ( http://www.s-k.com/pages/pro_01_01.html ) How old is the mixer? There may be a cam that has worn out not allowing the hot to open as far. I'd not expect large particles to get past the cylinder or pressure reducing valve - so unless there is calcium buildup in your hot water line (Maybe there is and a chunk broke off, lodging @ an elbow?) , that shouldn't clog the pipe up. It sounds like your overflow is a relief valve in the PRV - or is it a long pipe 10 ft or so above the roof ? An open pipe going above the roof is pretty much failure proof. 1 PSI = 27.7 inches of head (H20), so that might be out for your supply pressures. I'd be inclined to fix it up using the washer - then look at pressures before and after the PRV, and at the shower head (Hot & Cold, static and running) - and keep a log until the problem cropped up again. It does seem an odd way to plumb it these days, usually that setup will result in people gettting scalded/frozen whenever a tap is turned on. AFAIK shower mixers run better with even pressure. Been about 10+ years since my time @ a plumber/plumbing supply house. >>> rhprosser@gmail.com 24 Mar 08 15:16:00 >>> Hi Eoin No, Only the hot water goes through the reducing valve. The cold water runs at mains pressure (and the shower mixer is designed to accomodate that). The plumber claimed that setting it up this way allowed the cold water to "pull" the hot water through the system and actually increased the haot water flow rate. I guess it would happen if there was a low pressure area in the mixer - similar to a siphon effect. The filter screen on the shower mixer (hot water) has been removed as it was introducing an additional pressure drop. That was done about 3 years ago and so far I've only had to clean out the mixer once. RP On 25/03/2008, Eoin Ross wrote: > Is the HOT/COLD pressure the same @ the shower (While flowing)? > > Sounds like you have a flow restriction on the hot water side of the shower - possible swarf/grit has found its way to a screen on the hot side shower valve? It may help to think of Pressure as Voltage, and Flow as current. Narrowed lines/blockages act like resistors. > > >>> rhprosser@gmail.com 24 Mar 08 02:58:04 >>> > On 24/03/2008, Bob Blick wrote: > > > > > I'm having a similar problem at the moment with a pressure reducing > valve. If I adjust it for reasonable pressure in the upstairs shower, > it eventually develops a slow leak and I start losing hot water > through the overflow. If I back off the pressure to stop the overflow, > then we get cold showers. A new washer generally fixes the problem for > about 6 months but that''s it. Not sign of grit or damage to the > sealing face where the washer sits. I've tried sanding the surface of > the washer which removes the hard oxydised surface and it appears to > help but it doesn't last > > We first noticed the problem when the council fitted a water meter and > there was grit/swarf in the system but that was a long time ago and it > now appears clean. > > One solution appears to be to increase the height of the overflow so > more back pressure will develop before it starts to drip. This will > apply more pressure to the valve & hopefully turn it off harder. But > I'm already close to the maximum pressure of the hot water cylendar. > > The good side of things is that it's an easy job to replace the washer. > > Any ideas? > > Richard P > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist