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General Plumbing and Gasfitting Talk => Ask Plumbers (Public) => Plumbing => Q & A - Hot Water Cylinders => Topic started by: blitzn on October 15, 2019, 06:30:37 PM

Title: HWC and Valve questions
Post by: blitzn on October 15, 2019, 06:30:37 PM: Hi All

I have a 135ltr 7.6mtr head, low pressure Reeem hot water cylinder in my house. I currently have a 3.6 KPA nefa pressure regulating valve under the house? I have a 4 mtr high (from the floor) copper line running out through the roof with a pressure relief valve attached. there are no markings or stickers on the pressure relief valve and is 15 years old im assuming it is a 3.6kpa one? This is not dripping or leaking water. I have attached a pressure gauge to my hot water line and it is only reading 4psi with outlets off (28kpa)

Questions are...

1 should i have a 7.6kpa Pressure Regulating Valve to match for this cylinder?
2 If i should have a 7.6kpa valve can i increase the 3.6kpa nefa valve to around 8-9psi (62kpa to be safe) on the hotwater side?
3 is it worth me replacing my relief valve on the rood to ensure it is a 3.6kpa valve?

Any help here would be appreciated
Cheers
Alan
Title: Re: HWC and Valve questions
Post by: Plumber on October 16, 2019, 09:38:07 AM: Hi Alan,

Obviously any recommendation and information provided cannot be taken as an absolute and will depend on various onsite conditions and knowledge which are not available to me. As such, before you endeavour to be "hands on" please get a registered plumber to have a look and confirm, even carry out any plumbing changes.

To answer your questions:

1) No, if you add 7.6 and the relief valve is rated below this it will start leaking (relieving pressure). You need someone to calculate total possible pressure in the system VS total achievable pressure and both valves (incoming and relief) need to match. Where the fixtures are within that available head also plays a role.

2) No, As per #1 you risk the overflow running or even exceeding the total system pressure which worse case scenario will result in your hot water cylinder bursting.

3) relief valves are not installed at the road, you may have this wrong and may be referring to the limiting valve? In any case this reinforces that you should get someone to look at your conditions and provide professional advice.

Another thing you may want to consider if you are looking for higher pressure is to simply replace the cylinder with a mains pressure tank. They are as cheap as 1900 installed these days. Any money you spend on valves etc could be going towards a new system.

I hope this helps.
Title: Re: HWC and Valve questions
Post by: blitzn on October 16, 2019, 06:32:46 PM: Hi, Thanks for the prompt reply on this. Will leave the system as is for now. Currently hunting around to go mains pressure as you said. Think this will be the best option over all. Cheers