As Subject: Are PRV's generally fitted as a whole house device in the rising main or as seperate devices in the DHW and Cold supplies?
(*) And I really do mean milky, not just a bit of grey cloudiness that quickly clears this takes quite a while to clear and the water does look like milk.
Often seen on the inlet to unvented cylinders. It would make sense to take the houshold cold feeds from after the PRV if feeding showers etc.
Erm, have we missed something?
I think the recent strange loss ofcontact by news servers may have resulted in missing posts. Brian
No John is responding to the root message of the thread posted by me.
Yeah, it's the shower that is going to be the problem. I don't like high pressure low volume ones, low pressure high volume is much better. I don't like the idea of no stored water, so don't particularly want to go to an all "mains" system, even with PRV(s). But on the other hand I don't want stored water that is not regularly changed.
Mains water only arrived here about 30 years ago, before that it was pumped up from the farm below and was unreliable. So *all* the water used here goes through 150 gallons of storeage tanks in one of the lofts. The only place the rising main fed until the other month was those tanks. Yeah I know at least the kitchen tap should be on the mains but we've been here 12 years with no ill effects. I did properly cover them and remove building debris, dead mouse and various dead insects fairly soon after moving in though.
With 150 gallons of stored water and no means of knowing if the mains water is on or off I don't know how reliable the mains water supply is, or isn't... Bit of a rock and a hard place.
does
Maybe. The DHW is heated via a coil in the thermal store, this is fed direct mains pressure and has a thermostatic mixer valve on the output to limit the maximum temperature of the DHW. The store runs at
80C just under 1/2 way up, the top will be rather hotter.When you heat water it can no longer hold as much disolved air, in an unvented system this just escapes up the vent pipe. In this system the air stays disolved due to the (relatively) high pressure, when you release the pressure at a tap it comes out of solution, like taking the top of the bottle of pop. The bubbles formed are very fine and there are lots of them so the water looks milky, give it 30 seconds to a minute and it clears.
Do "mains pressure" combis actually contain a PRV to limit the pressure in the heat exchanger and at the taps? Not to mention limiting the flow rate so they stand half a chance of performing.
How does an "unvented" stored hotwater system deal with this dissolved air?
Nope, mains pressure has been measured at 4.5 bar. This is rather close to the 5 bar maximum for the HW side of the thermal store for my likeing though.
Only air, haven't had to descale the kettle here since they switched our water supply from an adit a mile away to Burnhope Reservoir several years ago.
In article , Dave Liquorice writes
Still not entirely sure what the question is but could the answer be one or more pressure balancing valves rather than PRVs? See:
In the case of an unvented cylinder, ALL cold tap feeds should be taken AFTER the PRV, so that the cold pressure is the same as the hot pressure.
Mixer taps and showers will back feed if the cold is at rising main pressure and the hot at ~3bar plus the danger of shower temps going up and down as taps are turned on / off etc...
Tim.
Most combis can operate to 10 bar and have no PRV.
High flow combis are around. Look at the Intergas. Assuming you have gas. It is medium flow at most but super reliable with only 4 moving parts. Built like a tank.
Look at the higher flow ATAG E325ec with the integrated gas saver. Fit the Brain with it and the outside temp sensor. They are "very" cheap to run and a class act,
You can have the combi off the 150 gallon tank using a whole house pump. But if the flow pressure is good on the mains stick to the mains and use their pump. The cold tank can be used for toilets and cold fill d/w & washing machines to avoid robbing the shower of flow and pressure and backup in case.
It is best you fit flow regulators on a mains pressure system to "balance" the H&C supply. BES sell these and they are integrated isolators as well. On the kitchen you will only need a 6 litre/min cartridge on hot and cold supplies. Many outlets like basins, washing machines and toilets need less - fast filling is not an issue with those. Keep the bath and showers unregulated to ensure they are not robbed of flow and pressure.
Make sure a dedicated 22mm pipe is run from the stop c*ck to the combi/unvented cylinder or thermal store. Avoid an unvented cylinder, they need a G3 man to fit and service it once a year. If you want stored hot water then go for vented thermal store with the CH take off an internal coil to avoid sludge build up in the store. Get back to me if you want a spec.
It doesn't. It can come out milky.
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