Browse Forums Bathrooms and Laundry 1 Jul 06, 2009 1:32 pm Hi, I have a very reliable gravity fed hot water system and the flow rate is becoming an issue for a new shower head assembly purchased as part of a bathroom renovation which has a fixed 9 l/min flow controller (and which can’t be removed). The gravity system is very reliable and in over 40 years there have been no issues, so I am reluctant to replace it. I have had an idea and wanted to run it past you guys for your input. As you would all be aware, the system is comprised of a copper cistern in the roof space plumbed outside to the storage unit. The water pressure is therefore determined by the water head. I am thinking, instead of having the water pressure dependant on gravity and difference in height of roof cistern and outlet, could I connect a flow reduction device, like a 9 l/min or like flow controller between the 1/2 inch copper mains leading to the cistern and the 3/4 inch copper outlet plumbed to the storage tank, thereby removing the need for the copper cistern in the roof space. I am hoping that this arrangement would therefore increase the water pressure of the hot water to some level. I hope this makes sense. My question is a) Is this possible, will it work? b) Is such a setup with its higher pressure (although reduced), going to have an issue on the outside storage tank or its plumbing? c) When the taps are all shut, is the constant higher water pressure going to cause on issue on the outside storage tank. d) Are there any other problems that you guys can see with doing this? Thank you for any feedback in advance. Nick. Re: Conversion of a Gravity fed system - will it work??? 2Jul 07, 2009 12:04 am You can't install a flow restriction device at all on gravity-fed hot water. Won't work, regardless of how you try and plumb it. You also can't use flow-restricted showerheads on gravity-fed. You need to change to a mains-pressure system. Judie Re: Conversion of a Gravity fed system - will it work??? 3Jul 07, 2009 12:13 am Or a presure pump Where you are coming from is where you are going to... Re: Conversion of a Gravity fed system - will it work??? 4Jul 07, 2009 9:12 am Judie You can't install a flow restriction device at all on gravity-fed hot water. Won't work, regardless of how you try and plumb it. You also can't use flow-restricted showerheads on gravity-fed. You need to change to a mains-pressure system. Judie Hi Jodie and thanks for your response. I just want to clarify that I would not be requiring the cistern in the room space with this setup, therefore the hot water system will not operate as a gravity fed system, rather a reduced mains pressure system. Essentially I am asking if I can plumb the mains pressure (flow restricted to 9 l/min) directly to the outside storage tank .... with no cistern in roof, hence no gravity. This would mean that the pressure head of the water supplied to all jumper valves be 9 l/min. So I am not looking at adding a flow restriction device ONTO gravity hot water, but rather removing the cistern which makes the system gravity fed and plumbing it directly to mains. So any chance this idea has merit? Hope this clears up any confusion. Thanks once again. Re: Conversion of a Gravity fed system - will it work??? 5Jul 16, 2009 3:52 pm What youre asking isnt really possible. The hotwater unit has to have some sort of pressure relief system on it. If its fed from a supply tank in or on the roof it more than likely has an expansion pipe that rises from the hot water unit to a point above the roof tank. If you bypassed the supply tank and connected mains pressure to the HWunit, you would need an expansion pipe that rose up very very high, otherwise water would continually discharge from the expansion pipe. Your confusing flow restrictors with pressure reduction or limiting valves. A flow restrictor will not drop pressure. It only allows for the flow to be reduced. There are however, sets of pressure reduction valves and relief valves that can be used on low pressure hot water units to enable them to be used on mains pressure hot water units. They are (or at least were) sold in pairs and were carefully calibrated to work in tanden, so to speak. The inlet valve dropping the pressure down from mains pressure to a workable low pressure and the outlet valve allowing for water to discharge when the pressure in system built up. I doubt that these valves are made anymore and when they lost calibration the tank burst. To overcome your shower problem you need to take out the flow restrictor within the shower rose. Its quite easy. Re: Conversion of a Gravity fed system - will it work??? 6Jul 16, 2009 11:48 pm vvs mand What youre asking isnt really possible. The hotwater unit has to have some sort of pressure relief system on it. If its fed from a supply tank in or on the roof it more than likely has an expansion pipe that rises from the hot water unit to a point above the roof tank. If you bypassed the supply tank and connected mains pressure to the HWunit, you would need an expansion pipe that rose up very very high, otherwise water would continually discharge from the expansion pipe. Your confusing flow restrictors with pressure reduction or limiting valves. A flow restrictor will not drop pressure. It only allows for the flow to be reduced. There are however, sets of pressure reduction valves and relief valves that can be used on low pressure hot water units to enable them to be used on mains pressure hot water units. They are (or at least were) sold in pairs and were carefully calibrated to work in tanden, so to speak. The inlet valve dropping the pressure down from mains pressure to a workable low pressure and the outlet valve allowing for water to discharge when the pressure in system built up. I doubt that these valves are made anymore and when they lost calibration the tank burst. To overcome your shower problem you need to take out the flow restrictor within the shower rose. Its quite easy. Thank-you very much for your response, much appreciated. I understand this issue now, thanks for clearing that up. Just a final question. From what I am hearing its really pairing up the pressure reduction valve with the relief valve and getting the calibration on the relief value correct. If in contrast, no pressure reduction valve was used and instead mains pressure plumbed directly to the tank and the relief valve was a mains pressure relief valve and attached directly to the tank (instead of at the end of a pipe in the roof space), would this solve the problem? I imagine if it is plumbed in this fashion, then it would essentially become a mains pressured electric hot water unit ... is there still fear that the tank would explode at the seams as it wasn't made for main pressure? Cheers. Re: Conversion of a Gravity fed system - will it work??? 7Jul 18, 2009 9:44 pm I havent seen a low pressure hot water unit for over 25 years. The ones I installed/ worked on were not designed for mains pressure and if mains pressure was connected directly to them would have burst. They wouldnt explode or anything, just burst. From the information you've given, more than likely the same would happen. It depends on water the unit was designed for. The manufacturers specification on the unit should tell you what pressures it was designed for. To go outside these specifications is inviting disaster. You should be aware of the fact, that if you tamper or modify the unit and it bursts and floods your house, your insurance company might void your insurance, firstly because youre not a licenced plumber and secondly because the unit was modified outside of the manufacturer's specifications. From the information posted it looks to me your rumpus room is nothing more than extended garage. That will present a number of challenges. Single brick wall between… 2 7771 Hi, Apologies - I know there is plenty out there on this but struggling to put together the puzzle. We're planning our garage/external laundry to master bedroom and… 0 11121 Because it only states 90mm not if it’s 45mm or 35mm and yes I do have the plans my question was specifically since it’s not the structural value and only to hold… 2 3515 |