Hot water overflowing onto roof

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bit, Aug 3, 5:00am
It overflows even when the water is cold.
I can turn the flow down at the ajax valve but it has to be so low we can't get any water from the hot taps and the water still overflows onto the roof.

Any ideas?

arabelle, Aug 3, 5:57am
got dirt in your NEFA valve, so keeping the flow open. or your AJAX is kaput, Ive had major problems with overflow happening, so now work the hotwater cylinder manually, only open it when I want to do the dishes or have a shower. the new AJAX didnt do a thing but empty my wallet. Mine only happens occasionally . .
When my new water tank went in about 18yrs ago I got the plumber to add a inlet tap, so get one of those for future planning if you dont have one now. but yup a plumbers job Im afraid, if its not the NEFA

hulloitsme, Aug 3, 5:58am
The Ajax valve is stuffed. Replace it.

If you have an Ajax valve that is leaking, there are a few things you can do to fix the problem. Here are some steps you can take:

1. Turn off the water supply: The first step is to turn off the water supply to the valve. This will prevent any further water from leaking out and causing damage.
2. Disassemble the valve: Use a wrench or pliers to remove the valve from the pipe. Carefully disassemble the valve, taking note of the order in which the parts are assembled.
3. Inspect the valve: Check the valve for any cracks, damage, or wear and tear. If the valve is damaged, it may need to be replaced.
4. Replace the valve washer: If the valve appears to be in good condition, the problem may be with the valve washer. Replace the washer with a new one that is the same size and shape.
5. Reassemble the valve: Once you have replaced the washer or made any necessary repairs, reassemble the valve in the reverse order of how it was disassembled. Tighten the valve with a wrench or pliers, making sure not to over-tighten.
6. Turn on the water supply: Turn on the water supply and check for any leaks. If the valve is still leaking, you may need to repeat the process or call a professional plumber for assistance.

Remember, if you are not comfortable working with plumbing or valve repairs, it's always best to call a professional for help. A leaky valve can cause water damage and other issues, so it's important to address the problem as soon as possible to avoid any further damage.

bit, Aug 3, 8:52am
But I can adjust the ajax valve. That's what I don't understand. But I can't see any other valve. Where should I find the NEFA?
The plumber said he will come sometime this week. 😅
I'm on mains. There's a tap at the road. Inlet tap on your water tank? Between the tank and the house right? Or otherwise I guess your tank is not filled with rain water.

lythande1, Aug 3, 8:54am
There are no "ajax" valves anymore.
However the valve needs replacing.

amasser, Aug 3, 9:56am
Pressure-reducing valves, Nefa or Ajax (Apex) brands but it might be the washer that needs replacing. Had this done recently and saved the cost of a new valve.

trade4us2, Aug 3, 12:40pm
The old Ajax valves are perfectly OK. The rubber diaphragm is probably perished. A new diaphragm cost me $15 last time I bought one. The new ones are probably synthetic rubber and will last forever.

hulloitsme, Aug 3, 6:33pm
Good point! OP needs to check the diaphragm first.

dastedly, Aug 3, 9:42pm
Ajax valves have not been made for about 1960s you can not get parts for them . There is valve called pressure reducing valve. The time and the rate of trademan take P/R valve and replace .better off putting new one

marte, Aug 4, 1:59am
Check that the overflow pipe hasn't split because for a frost or something like that.
It's happened to me before.

mrfxit, Aug 5, 7:34am
Pedantics, Same device different name
pressure reducing valve
pressure reduction valve
pressure regulator valve
pressure relief valve
proportional pressure reducing valve
Pressure constriction valve

Most ppl still call every adjustable spanner a "Crescent" but we all know what it is regardless of the name

brittsyl, Aug 5, 12:03pm
We have had this problem since installing a fire with wet back, got the plumber back, he installed a "special" valve. He said it might work or not. It didnt work. Huge amounts of water are wasted. Wondering if connecting water radiators would help.

mrfxit, Aug 5, 1:58pm
Wetback systems normally need a higher vent pipe AND possibly a pressure relief valve on top.
Last time I had to set up a wetback system, I used a larger & longer vent pipe then std.
That sorted it

dastedly, Aug 5, 8:46pm
It is a big no no to put a relief valve on wetback . Must be open vent , as it is classed as a un control heat.

dee238, Aug 6, 2:00am
I had this problem two years ago. It was due to a worn out washer. Was replaced and problem solved.

mrfxit, Aug 6, 6:17pm
I think the std pipe is 1/2" copper & the one I used was 3/4".
Seem to do the trick ok,
When the cylinder boiled, it just spat the water out as expected

marte, Aug 6, 10:45pm
A friend's watertank was boiling over with their wetback going as I got there.
I told them & so 2 of them had showers & then the water went cold. It's a big water cylinder.
What would cause a wetback to boil the water out the overflow, but not heat up the whole cylinder of hot water?
It's a later model, 5 years +? Logburner. Electricity & wetback going at the same time.

Using just a little destructor wetback, 5 of us could have showers in one run if I got it going just before the first shower. With a medium tank, no insulation, so old it was riveted at the ends.

tegretol, Aug 7, 10:02am
Or even a small lump of grit in it will produce this behaviour. Simple to dismantle and clean out and replace the diaphram if required.

But if you have a plumber coming, why even ask? He will replace the valve and take away your old one for the next customer and you will pay the standard $400 fee.

mrfxit, Aug 7, 11:21am
Could be an air lock in the piping somewhere
OR
It's an old cylinder with side entry pipes placed too high
OR
The amount of hot water pushed out, allowed far too much cold water back in.

Sounds a bit like an over active heating system.
I used to get that if I had the fire stocked up too hot for too long

marte, Aug 7, 4:41pm
It was weird, how it went cold so quickly and just before it was violently boiling water out onto the roof.
The systems like 6 years old & all done at the same time, so its all new, 6 years ago.
The in & out pipes were not fantastically hot & there's not much temp difference between them, but the pipes are lowish & have enough slope.

I as thinking that some sort of sediment in the wetback was causing 'bumping'.
A friend had the same fireplace & his took ages to heat up the water, it's really just a accessory to the electric, rather than the prime heating source.

bit, Aug 8, 12:47pm
Neither of the plumbers I called have come out.
OK so I fitted out the pressure reducing valve with new diaphragm and washer. It's an Apex 3.7 model.
While I had it removed the hot water cylinder was leaking into a bucket because the tap wouldn't close fully. Now I've reconnected and turned on the water at the mains just enough to get reasonable flow from the cold taps. I've opened the tap between the valve and hot water cylinder enough to hear a reasonable flow and I guess the cylinder is filling back up because there's nothing coming from the hot taps yet.

(Edit. Correction. I have water flow from the hot taps and water flowing onto my roof again. I'm trying another plumber)

trade4us2, Aug 8, 4:25pm
There should be a screw under the Apex valve. When you screw it out the water flow should stop. 3.7 metres seems a bit low, but it depends on the rating for the cylinder.

tegretol, Aug 8, 11:14pm
Well no, it depends on the roof height! Some very low bungalows let go at 3m if they have a very low pitch.

budgel, Aug 9, 11:00am
Water head is not determined by the roof height, it is for delivering the required pressure at the taps.

tegretol, Aug 9, 1:27pm
That I know but if you have pressure equating to more head than the overflow pipe then it will flow out! For example, if you set your valve up to output 6.7m of head (about 10psi) but the top of the outlet is only 4m above the valve, you'll have hot water pissing out. So the higher the building/overflow pipe, the higher you can set the ajax. Or perhaps a 7m pipe sticking out of the top of a 3m high building would be OK?