Bought house many years ago and have only ever used one shower.
There are two showers, each with the same type of mixer. Using one shower is fine but two at same time not fine. The system is a low pressure hot (header tank - 6psi at shower head) with mains (reduced to 40psi) and when second shower is turned on, the first runs cold and needs the mixer to be almost full hot.
What I suspect is happening is that when the second mixer is turned on, cold water is getting pushed back up the hot feed and into the first mixer, thus requiring the first to be turned right round to hot.
Now, the question is will a one-way valve in the hot feeds fix this? How much reverse flow is required to activate such devices?
The previous owner said that a local plumber told him that the only way to fix it would be to install a second hot water cylinder - yeah right!
Be interested if anyone has similar experiences.
bill1451,
May 18, 1:42am
Maybe worth investigating the fitting of a booster pump on the outlet of the HWCyl. These are only about 100watts to run, but from what I read they are a cost effecctive solution vs a high pressure cyl at prob $2000.
tweake,
May 18, 1:50am
sounds more like low pressure. try turning a hot tap on while the shower is on. if it runs cold then it will be pressure. probably have to change the cold water feed to the hot water cylinder side of the pressure regulator. that way both hot and cold are the same pressure. so when the other shower turns on both hot and cold loose pressure, not just the hot.
moltenfire,
May 18, 1:54am
There is already a booster pump which increases the flow (not the pressure) and using one shower, it works a treat. But to solve this issue by the use of pressure, wouldn't the hot need to be increased to equal the cold?
moltenfire,
May 18, 1:55am
It's a low pressure HWC. Turning on a hot tap doesn't affect the shower (one only running) as the booster pump takes care of that. Prior to the pump installation, using a hot tap did affect the shower. But this is now an issue of the second shower affecting the first.
tweake,
May 18, 2:09am
is that in a double shower or two completely separate showers?
moltenfire,
May 18, 2:28am
Two completely separate showers, about 10m apart.
tweake,
May 18, 2:36am
a small test on your earlier theory. turn both showers on but on the 2nd one take the shower head off. that should stop cold water pressure from going back up the hot line and hopefully prove/disprove the theory.
i assume the booster pump is on a ring circuit, ie it pumps hot water around and back to the tank so each outlet as very little delay in getting hot water.
i'm still thinking its more pressure related. is there anyway of plumbing the colds back to the pressure regulator?
moltenfire,
May 18, 2:56am
Thanks. Yep removing the shower head does reduce (by about 50%) the issue as the first shower is now ok at about the 7 o'clock (as opposed to the 9 o'clock) position. With the second shower off, the first is fine at the vertical 12 o'clock position.
The colds are fed from the pressure regulator (the mains off the street fluctuates can can reach 110psi) which provides a constant 40psi out.
The booster is at the HWC outlet so feeds both showers. It also feeds all hot taps and was fitted to stop the use of a hot tap from affecting the shower - that worked fine.
I wonder if a second pump on the second shower only might fix this? Although I go back to my first question re one-way valves - will one of these stop the cold from forcing backwards up the hot line from the mixer?
tweake,
May 18, 3:33am
ok, sounds like your theory is correct. one way valve won't fix it as such. the first shower will be fine but 2nd shower will run totally cold and be usable.
try a simply fix, inside the shower mixer on the 2nd shower will be flow controls. adjust the cold one right down so its pressure is low.
if your booster pump is not on a ring circuit, get one that outputs higher pressure. you need to get close to cold water pressure.
regulators, you should have two. one for dropping mains pressure down to 40psi and feeding the hot water cylinder set to 6 psi or so. either replumb the cold water to hot water regulator so cold water is at 6psi or change booster pump to increase hot water pressure in the pipes to 40psi.
cagivachick1,
May 18, 3:46am
hi linda
moltenfire,
May 21, 9:52pm
Why won't that idea work? Wouldn't he one-way valve allow hot flow into the mixer but prevent cold from flowing back out of the hot feed?
tweake,
May 22, 1:06am
for the cold water to go back up the hot line, that shower will be running cold. a one way valve will stop cold going back up the line but the cold water pressure will continue to stop any hot coming out.
i suspect the problem is the cold water pressure is to high in the 2nd shower and the bottle neck at the shower head creates pressure between mixer and the head which is higher than the hot water pressure, so it pushes back up the hot line. if you adjust the mixer regulator it should drop cold pressure enough so it doesn't create pressure between the mixer and head. ie turn the cold side flow adjustment down until the cold flow from head starts to reduce. (if i remember correctly).
moltenfire,
May 22, 6:56am
Ah thanks. But there is no adjuster anywhere on the mixer body. Methven.
tweake,
May 22, 8:09pm
what make/model shower unit?
moltenfire,
May 24, 8:28pm
previous owner didn't leave packaging here so no idea. But it's a Methven solid brass body with the plastic mixing assy that comes out of the front. Def no adjustables anywhere one it.
tweake,
Jan 2, 5:50am
looking through their site it looks like they have changeable jets on the outlet, which you probably can't change without removing the shower lining. the standard jet should work with your water pressure.
there is also a flow adjustment but no mention on what exactly it adjusts. that in the center of the handle shaft. probably allen key, rotate right to decrease flow.
site does mention they make high pressure and all pressure mixers. i wonder if someone fitted a high pressure mixer by mistake.
i think your going to have to try and find what model mixer it is. even if it means trawling goggle images.
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