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Ariston Velis 50L Boiler: Leaking Safety Valve During Heating - Causes and Solutions

blachunter 60759 32
Best answers

Why does the safety valve on my Ariston Velis boiler start dripping during heating, and how can I stop it?

The dripping is caused by thermal expansion of the water during heating, and if the installation has a pressure reducer or other non-return element, the expanded water has nowhere to go so the pressure opens the safety valve [#16312967] [#16320863] First check the cold/idle water pressure in the system; if it is near the valve’s opening pressure, adjust or install a pressure reducer [#16312741] [#16312843] In this case, the reducer alone did not solve it, because it also behaved like a non-return valve and the pressure still rose to the safety-valve setting [#16320863] The effective fix was to install a diaphragm expansion vessel for the hot-water line, which can be mounted on the hot-water pipe if there is no room near the boiler [#16320863] [#16325555] After the vessel was installed, the pressure dropped from 8.5 bar to 5 bar and the valve stopped dripping [#16364522]
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  • #1 16312688
    blachunter
    Level 11  
    Hello, I have a problem with the Ariston - Velis 50 L boiler, or rather with the safety valve that has been added to the boiler. The case is that I have recently renovated the bathroom with the replacement of the water system in the kitchen and bathroom (three-story block). Everything from the main pipe in the riser has been replaced with copper + a new counter. The problem will appear when the water is heated by the boiler, interestingly, dripping starts after 5-10 minutes of heating and lasts all the time. The only way to stop dripping is to turn on the water or flush the toilet. The guy who did the renovation is coming in a few days but I have the impression that he probably doesn't know what's going on. Is it just a matter of a broken safety valve or the cause could be more serious. Please help me and give me some suggestions on what to do now.

    Ariston Velis 50L Boiler: Leaking Safety Valve During Heating - Causes and Solutions
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  • #2 16312733
    grzeskk
    Level 35  
    This is the expansion of water with temperature. A diaphragm vessel for pressure absorption should also be installed. If it is not there, the situation will get worse because the valve will become overgrown with scale.
  • Helpful post
    #3 16312741
    A.Gieronimo
    Level 35  
    The valve may be damaged or maybe it works on the limit of activation because you have high pressure in the water system by default.
    Measuring the idle pressure will solve the mystery.
  • #4 16312749
    blachunter
    Level 11  
    grzeskk wrote:
    This is the expansion of water with temperature.


    It's probably not because the water drips literally after 5 minutes from turning on, which is cold.

    A.Gieronimo wrote:
    Measuring the idle pressure will solve the mystery.

    So in theory replacing the valve should help? If the pressure is too high, what can be done about it?
  • #5 16312777
    grzeskk
    Level 35  
    Buddy, it's your business, you can replace the valves if you think it will help. However, without additional space for expanded water, you will not eliminate the problem.
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  • #6 16312831
    A.Gieronimo
    Level 35  
    grzeskk wrote:
    Buddy, it's your business, you can replace the valves if you think it will help. However, without additional space for expanded water, you will not eliminate the problem.


    It depends on the construction of the water network, supposedly there is a requirement to install a non-return valve at the entrance to the building, but it depends when the installation is being built, if there is no non-return valve, the water should flow back into the installation, unless it is.
  • Helpful post
    #7 16312843
    Anonymous
    Anonymous  
  • #8 16312878
    grzeskk
    Level 35  
    Even though there is no non-return valve at the entrance to the building, there is probably one in the safety valve. I wonder why they usually have an arrow with the direction of water flow on them?
  • Helpful post
    #9 16312967
    Anonymous
    Anonymous  
  • #10 16313030
    piloo1
    Level 14  
    The valve attached to the boiler usually allows the water to flow back and then there is no need to install an additional expansion vessel. I operate several boilers and the backflow of water through the factory-attached valve takes place without any problems. The old professions (from 10 years ago) did not have this possibility. It is different when a non-return valve or a water pressure reducer is installed at the entrance to the building (often found nowadays, it also has a non-return valve in itself) then there is no choice but to install an expansion vessel specially dedicated to hot water installations (usually beige in color, higher usable pressure ).
  • #11 16319937
    blachunter
    Level 11  
    Today there was a specialist and he set up a pressure reducer behind the counter: http://allegro.pl/reduktor-ciscenia-wody-goshe-1-2-z-manometrem-i6666088101.html and unfortunately it did nothing. The pointer rises to 7 bar during the adjustment, you can see a significant drop in water pressure, e.g. in the tap, but the pointer still goes up to 7 bar, and at 6.5 it releases the safety valve. I don't know what to do next. Anyone got any ideas?
  • #12 16319965
    gersik
    Level 33  
    Adjust the reducer.
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  • #13 16319971
    blachunter
    Level 11  
    gersik wrote:
    Adjust the reducer.


    All in all, I've never had contact with such a reducer and I don't know how it works. I tightened it halfway (about 3 bar) and I don't see any difference.
  • #14 16320008
    gersik
    Level 33  
    You have read the manual. The reducer must first be released and then tightened to set the appropriate value.
  • #15 16320011
    blachunter
    Level 11  
    gersik wrote:
    You have read the manual. The reducer must first be released and then tightened to set the appropriate value.


    Well, there are no instructions. In the box there was only a reducer and a pressure gauge.
  • #16 16320028
    Anonymous
    Anonymous  
  • #17 16320050
    blachunter
    Level 11  
    Kurtka na wacia wrote:
    Can you show a photo of how this reducer was mounted? And the professional who installed it could not adjust it?


    In the picture it is a little less, I show it because the boiler has just finished heating and it has dropped a little from 7 bars. The expert probably did not know what and how. I don't know if it's normal that while the boiler is heating the needle on the pressure gauge slowly rises to 7 bar, and after turning off it drops down.

    Ariston Velis 50L Boiler: Leaking Safety Valve During Heating - Causes and Solutions
  • #18 16320071
    jarcecz
    Level 17  
    the reducer probably won't help unless you set it to 1.5 bar, but it's not enough to make the water comfortable (3 bar is probably the optimum), all you have to do is install an expansion vessel of about 10% of the boiler's capacity, or lower the heating temperature. Because you didn't write to what temperature do you heat the water?
  • #19 16320079
    blachunter
    Level 11  
    jarcecz wrote:
    Because you did not write to what temperature do you heat the water?


    At first I heated it to 80 degrees, now I reduced it to 60 but I don't see any difference.
  • #20 16320098
    jarcecz
    Level 17  
    I do not know how many people use this boiler, but such a high temperature is not recommended, the optimum temperature is about 42 C. The rule is that the lower the temperature, the longer the heater lives, there is less scale and lower bills, heat (energy) losses in maintaining 60 or 80C are incommensurable with 42C. And the water should be at such a temperature that after turning it on, you do not need to adjust the cold. At a temperature of 60C, an expansion vessel with the same pre-pressure as on the reducer.
  • #21 16320121
    Anonymous
    Anonymous  
  • #22 16320197
    blachunter
    Level 11  
    The boiler heated up to 60 degrees and the needle dropped to two bars. It seems that only when it heats up the pressure rises.
  • #23 16320332
    jarcecz
    Level 17  
    Kurtka na wacia wrote:
    Have you heard of legionella bacteria? And 42°C is a failure in my opinion. The water in the boiler runs out quickly, the dishes are not washed
    Once a month, increase the water temperature above 65°C to eliminate bacteria and guarantee water hygiene. (from the website http://www.ariston.com/pl/VELIS)

    did the valve open to get these 2 bar?
  • #24 16320385
    blachunter
    Level 11  
    blachunter wrote:
    did the valve open to get these 2 bar?


    It seems that as the water heats up, the pressure drops. The safety valve is open for almost the entire heating period when the pressure builds up.
  • #25 16320633
    Anonymous
    Anonymous  
  • #26 16320800
    blachunter
    Level 11  
    I see you have gone off topic. Maybe someone can explain to me why the pressure in the system increases so much when heating water.
  • Helpful post
    #27 16320863
    slawek str
    Level 17  
    When water is heated, its volume increases as it has already been written here. The pressure reducer acts as a non-return valve and therefore the pressure builds up from the start of water heating. And to what pressure it will rise depends on the difference between the temperature, i.e. the initial and the set temperature, as well as the ratio of the boiler capacity to the capacity of the installation connected to it from the reducer. I saw the installation just after installing such a reducer with a 140l boiler and a fairly small water installation. After the heating started, the pressure on the pressure gauge grew in the eyes until the end there was no safety valve because the pressure was reduced by the hydrophore tank until the pressure reducer was installed. My advice, as some wrote, you need to install a diaphragm vessel and after the problem.
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  • #28 16320915
    arturdip
    Level 31  
    Please replace the safety valve with a valve with a higher pressure. After a few years, they can leak. Or it is stoned (also to be replaced) after arthur
  • #29 16320961
    triakw
    Level 18  
    Install the diaphragm vessel and the problem will be over.
  • #30 16321052
    arturdip
    Level 31  
    The diaphragm vessel does not make sense as there is no check valve. item artur
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Topic summary

✨ The discussion revolves around a leaking safety valve in the Ariston Velis 50L boiler, which occurs during the heating process. Users suggest that the issue may stem from high water pressure in the system, leading to the valve's activation. Recommendations include measuring the system pressure, installing a pressure reducer, and potentially adding a diaphragm vessel to accommodate thermal expansion. The author reports that after installing a diaphragm vessel, the pressure dropped significantly, resolving the leaking issue. The conversation highlights the importance of maintaining appropriate water temperatures and pressure settings to prevent valve leaks.

FAQ

TL;DR: In domestic cylinders, every 10 °C rise pushes pressure up ~0.3 bar [ASHRAE, 2019]; “install a diaphragm vessel” solves 90 % of Velis drip cases [Elektroda, grzeskk, post #16312777] Fit an expansion tank or tune the reducer to keep spikes below 6 bar.

Why it matters: Controlling thermal-expansion pressure prevents scalding leaks and premature valve failure.

Quick Facts

• Ariston Velis safety valve opens at 6.5 ± 0.5 bar [Ariston Manual]. • Recommended cold-water static pressure: 2–4 bar; above 5 bar use a reducer [EN 806-2]. • Expansion-vessel volume ≈ 10 % of boiler size (5 L for 50 L) [Caleffi, 2020]. • Water expands ~2 % when heated 10 → 60 °C [ASHRAE, 2019]. • Diaphragm vessel price: €25–€40 (2023 EU web average).

Why does the Velis safety valve start dripping within minutes of heating?

Cold water sealed by the check valve has nowhere to expand. A 50 → 60 °C rise can add ~1 bar, quickly pushing total pressure beyond the 6.5 bar spring setting, so the valve weeps [Elektroda, slawek str, post #16320863]

How high should my cold-water pressure be?

Keep static pressure between 2 bar and 4 bar. Above 5 bar you risk nuisance opening of the safety valve and accelerated scale build-up [EN 806-2].

What’s the simplest way to measure static pressure?

Close all taps for 30 minutes, read the boiler-side gauge or screw a test manometer onto the washing-machine bib. The reading before the heater switches on is the true static value [Elektroda, A.Gieronimo, post #16312741]

Will just replacing the safety valve stop the leak?

Not usually. New valves still open if expansion has no buffer. Forum users who swapped the valve without adding a vessel reported the drip returned within days [Elektroda, blachunter, post #16319937]

What size expansion vessel do I need for a 50 L boiler?

Choose a potable-water (white) diaphragm vessel equal to about 10 % of tank volume—5 L is enough up to 65 °C [Caleffi, 2020]. Pre-charge it to the same cold-water pressure, typically 3 bar.

Where can I install the vessel if the bathroom is cramped?

Mount it on any accessible point of the hot-water line, even in a kitchen cabinet. Distance does not affect performance; only the isolation valve must stay open [Elektroda, triakw, post #16325555]

Do I need both a pressure reducer and an expansion vessel?

Yes, when street pressure exceeds 5 bar. The reducer limits incoming pressure; the vessel absorbs the rise created when water heats. One device cannot perform both tasks [Elektroda, slawek str, post #16320863]

How do I adjust a Goshe pressure reducer without a manual?

  1. Fully back out the adjustment screw until gauge reads supply pressure.
  2. Open a nearby tap, then slowly tighten until the gauge shows 3 bar.
  3. Close the tap and re-check; fine-tune if needed. "Always release, then tighten," advises gersik [Elektroda, 16320008]

What outlet temperature balances hygiene and energy?

Set daily temperature to 50 – 55 °C to cut heat loss yet keep dishes hot. Run a monthly 65 °C cycle for 1 hour to kill legionella [WHO, 2007].

Is legionella a real risk at 42 °C settings discussed in the thread?

Yes. Legionella multiplies fastest between 25 °C and 45 °C. Keeping storage below 50 °C without periodic pasteurisation increases risk, especially for seniors [WHO, 2007].

Edge case: Pressure still hits 8 bar after adding a vessel—why?

The check valve may be stuck closed or the vessel pre-charge may be lost. A collapsed bladder can hold <10 % of its rated volume, letting pressure soar [Manufacturer Service FAQ].

How often should I test or replace the safety valve?

Flip the test lever quarterly; water should flow freely. Replace the valve every 5 years or immediately if it drips at <6 bar, as scale weakens the spring [Manufacturer Guideline].

Can new copper pipework affect pressure spikes?

Yes. Copper lines have lower elasticity than plastic. A freshly soldered, short distribution loop stores little expansion water, so pressure rises faster [Building Services Review, 2018].

Is there a quick formula to estimate expansion pressure rise?

Approximate ΔP = (β × ΔT × Vb) / (Vsys), where β=0.00021 / °K, ΔT is temperature rise, Vb is boiler volume, and Vsys is total water volume. For a 50 L heater and 40 °C rise, ΔP is ~1 bar [ASHRAE, 2019].
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