Hi Eoin On 25/03/2008, Eoin Ross wrote: > It is possible that there is an "inline eductor" in the mixer. ( http://www.s-k.com/pages/pro_01_01.html ) > There's nothing that looks like the diagram but there may be something in the design that produces a similar - but less efficient result. > How old is the mixer? There may be a cam that has worn out not allowing the hot to open as far. > The mixer would now be about 10-12 years old I guess. > 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. > Out water is quite soft. We don't get calcium buildup on anything. Even kettles etc don't scale. > 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 ? Long Pipe. Except it's only about 4ft above the roof line. The top of it is maybe 8metres above the hot water cylinder. I'm seriously considering lengthening it if I can but the cylinder is only rated for 10metres of head so I'll need to measure it. I don't want to burst the cylinder. > 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. Any hints about how to measure the pressure? I could buy a gauge but - being me -I'd prefer a homegrown solution that allowed datalogging! (e.g a strain guage tied to a plastic bottle connected to a tap ?) > > 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. Yes, we do get some variation in temperature when taps are turned on or off. But not dangerously so. Thanks for your help anyway. Richard P > > >>> 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 > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist