How to close these valves?

[gmc600]

Some advice would be appreciated here. I want to turn off these valves on the flow/return pipes under my Vokera Mynute i20 boiler to isolate the boiler and hopefully drain it without draining the full system, but how do you turn these? There’s a screw but can’t turn valve with a screwdriver and I also tried some pliers but the valve started to drip a little. I’m worried that if I turn too hard I’ll break something.

Thanks

 

[Madrab]

If they weep when turning then don't use them, old boiler isolation valve leak just for fun. If they've stopped weeping then you're lucky they usually continue to weep and the only fix is replacement.

If you want to try then use a spanner sized to the square or an adjustable spanner and they will go, twist through 90deg to turn off.

 

[gmc600]

Thanks, they are 9 years old, is that considered to be old for this type of valve? Are they just ball valves?

 

[Madrab]

Are they just ball valves

Yes - and because they get the constant hot/cold treatment and have chemicals running through them it impacts on the seals and when they are used the seals can weep.

9 yrs is enough time for them to be effected and as they won't have been used for 9yrs. It's a common issue.

 

[gmc600]

Thanks! Another query about expansion vessels rather than valves: I initially thought that CH and HW can both be heated at the same time but now I’m not sure, I suppose not as the temperature going to the radiators would be too high? I think my CH expansion vessel has an issue but is there a way to rule out the HW vessel also having a problem or do I need to check both? To check both looks like I’ll have to drain the whole system, tried to check without doing this but found out that this is not advised and will give incorrect pressure readings anyway. Are the two vessels usually hydraulically connected or isolated from one another? It’s not a combi, we have a HW tank and two heating zones, my understanding is that the zone valves are only on flow/return but not both so shouldn’t a working HW expansion vessel prevent pressure swings if the CH expansion vessel fails and vice versa? Noticed large swings in pressure recently. Pressure is now below 1 bar when cold and can get to over 3 when hot!

 

[Madrab]

Given it's a system boiler then yes, both of the more popular system configuration - S Plan and Y plan will allow both CH and HW to be run at the same time. Judging by your comments you may have an unvented cylinder and therefore will have an expansion vessel (EV) at the back of the boiler and a White/Blue EV somewhere near the cylinder?

The red EV controls the CH system pressure, that heats both the rads and the HW, the White/Blue EV is specifically for the unvented HW from the cylinder that is delivered to the taps, they are 2 completely separate systems and therefore would not interact.

If the large pressure swings are at the boiler then it will be the EV at the back of the boiler that needs tested and probably re-charged. You don't need to drain the CH system (all rads turned off) but you do need to de-pressurise it and then leave the system open to drain if the EV needs re-pressurised to release the pressure as the EV is pumped up. As the EV on that boiler is at the back of the boiler, so it could be tested and re-pressurised without taking the room sealed cover off and it does need a pressure gauge and a pump.

It is DIY'able if you are confident in performing the process and have the equipment.

 

[gmc600]

Thanks again, great explanation, I didn’t realise that the HW expansion vessel was on the cylinder/taps side. This raises another question - what would happen if this one had an issue?

I’ll try repressurising the one at the back of the boiler.

 

[Madrab]

I didn’t realise that the HW expansion vessel was on the cylinder/taps side

If you have an unvented cylinder then call a qualified unvented HW engineer (G3/HWSS ticket)

An unvented cylinder and it's ancillaries are all regulated and as such whoever works on in needs to hold the relative qualification.

The boiler one is fine, just remember to de-pressurise the CH system (Rads) before checking the vessel - pre charge for a typical CH system would be around 0.75>1bar. If the pre-charge it's too low or 0 then you need to leave a vent on a rad open or another point on the CH system to allow the release of pressure while inflating the vessel.