Old type gravity HW circuit brass safety valve.

[Richard C]

The old brass safety valve started leaking on my ageing gravity hot water system. Removed it easy enough but having trouble getting an immediate replacement locally as this type of valve doesn't seem to be used any more & the earliest my local plumbing supplier can get one is next week. The spring & body have cleaned up OK & the valve seat has lapped in perfectly so I’m pretty confident it will seal OK, the only thing I’m not sure of is if there is supposed to be a rubber seal or “O” ring between the valve faces. I couldn’t find the remains of any rubber seal/“O” ring in the valve body, just a load of black gunge - this could be the seal remains I suppose but am not convinced.

Can anyone familiar with these old safety valves tell me if the valve just seals, metal on metal or is there supposed to be a rubber seal or "O" ring in there?

 

[Nige F]

Metal to metal for sure

 

[Hot&Cold]

Richard C, them valves need setting up,doubt they come with instructions .

Tbh,if you called a heating technician in to deal with your leaking safety valve.After they had a look at your system and if appropriate they would just plug it off with a metal bsp plug.

 

[Richard C]

Many thanks Nige, I wasn't entirely sure so thought best to check as I'm very out of touch these days. I leak tested my "reconditioned" unit which held up under static pressure so at least that should get me through until the replacement arrives next week but, at just £3.95, it just seems ridiculous so I guess it really is "old stock" technology; but it still works so why change it, replacing the Fernox is going to cost me more!

 

[Richard C]

Many thanks for your reply Old&Cold & that was exactly my thinking! I'm not a "Heating Technician" but am a Mechanical Engineer & did work in Refrigeration Technology some 40 years ago. TBH, I don't really see the need for a vent on a non pressurised gravity HW loop if the CH loop is vented anyway; but maybe someone who knows better will tell me different!

It's basically a 50 year old copper pipework system but did have a high "high quality" replacement oil burner fitted some 16 years ago (still going strong) & was refurbished with a new HW cylinder, new radiators, tanks & a whole house pumped water system around 8 years ago. Apart from this small but rather inconvenient problem, the "old system" still works perfectly well & my thinking is, "if it aint really broke don't mess it about with it, just keep repairing it if you can. I can fix most old stuff myself so I'm loathe to modernise the whole system at great expense with "new technology" when it doesn't really need it. Modern "stuff" only seems to have a design life of around 5-7 years, anyway & always costs an arm & a leg to fix if/when it goes wrong & it will never, ever last 20 years let alone 50!

 

[spareshunter]

https://www.toolstation.com/shop/p7...feed&msclkid=67c9133eebd51aadcc32480b32a24045

It's there for a reason as the name suggests. Only to be used on low-pressure cistern fed systems. Cheap enough to replace than repair.

 

[JohnD]

It's there for a reason

Perhaps, 50 years ago, the reason used to be that there was a solid-fuel boiler

Which there no longer is.

 

[Richard C]

Yes they are cheap & I’ve been quoted around £3, just that my local supplier can’t get hold of one until next week. The repair was only ever going to be temporary &, unfortunately, the valve is still weeping very slightly but it will do until I can get a new one. Thanks for the link spareshunter, that’s even cheaper but, unfortunately, there is a £5 delivery charge!

 

[Terrywookfit]

Perhaps, 50 years ago, the reason used to be that there was a solid-fuel boiler

Which there no longer is.

There are still plenty of S/F boilers around.
During the 70's All council house boilers had a spring safety valve fitted, including Gas....Pretty pointless on an o/v system.
I have never known one to blow due to its design purpose.....The fookers just leak and drip for no apparent reason.

Apart from the previously mentioned "Council installs" where they were part of the spec and zealously checked by the COW....I have never installed one.

Fitted & replaced loads of "Nabics" though !!

 

[fixitflav]

The old brass safety valve started leaking on my ageing gravity hot water system. Removed it easy enough but having trouble getting an immediate replacement locally as this type of valve doesn't seem to be used any more & the earliest my local plumbing supplier can get one is next week. The spring & body have cleaned up OK & the valve seat has lapped in perfectly so I’m pretty confident it will seal OK, the only thing I’m not sure of is if there is supposed to be a rubber seal or “O” ring between the valve faces. I couldn’t find the remains of any rubber seal/“O” ring in the valve body, just a load of black gunge - this could be the seal remains I suppose but am not convinced.

Can anyone familiar with these old safety valves tell me if the valve just seals, metal on metal or is there supposed to be a rubber seal or "O" ring in there?

As others have said, as it's an open vented system you can just plug it. What size is it, 3/4BSP?

 

[Richard C]

Having had a temporary, 1/2" BSP blanking plug fitted for nearly a week & the hot water system working happily away every day without any problems or blowing up the system, I now have a new spring loaded, pressure relief valve.

Being a qualified Mechanical Engineer, my initial thoughts questioned the need for a pressure relief valve on a vented system, fed from a non-pressurised expansion loft tank & a couple of contributors have commented that one isn’t really necessary. A new valve will probably only leak again at some future date, it lives within a tiled kitchen riser so is not easily inspected/accessible without cutting a hole in the riser & the slow leak caused a lot of damage to the render/plaster on an adjacent, lounge wall before it became obvious something was wrong!

So I’m now in a bit of a dilemma & would like some additional thoughts/advice from CH Engineers/tradesmen; should I drain the system down again & fit the new valve or just leave the blanking plug in place, top up with inhibitor & forget it?

 

[Hugh Jaleak]

I did City & Guilds Plumbing Craft around 30 years ago, and remember being taught about the danger of boiler explosions should the feed & expansion pipes freeze, and the boiler stat fail. (Unlikely I know but wasn't unheard of at the time.) Our college teacher explained that fitting a safety valve would prevent a boiler exploding, and for what they cost, in his opinion, it was advisable to fit one on every system.

 

[Richard C]

I agree the cost is (very) minimal but the bloody things always seem to leak eventually &, as I’ve just experienced, can cause a disproportionate amount of damage if the leak isn’t spotted early.

I didn’t appreciate the possible danger of freezing pipes & simultaneous boiler thermostat failure but has this really ever happened in the recent past? It seems a bit 60’s, college “text book”! The last boiler stat I personally had fail was around 25 years ago & the boiler just went into “fail safe” mode. With modern heating controls, low temperature system monitoring & a modern(ish) boiler, maybe I’ve got more chance of a decent win on the lottery!

My thanks to those who have contributed so far; apologies for pushing it further but any more opinions/views?

Should I fit what seems to be rather, “Jurassic” technology & accept the possibility it will leak again or stick with the blanking plug & rely on the modern controls the system now has fitted?

 

[Nige F]

it lives within a tiled kitchen riser so is not easily inspected/accessible without cutting a hole in the riser & the slow leak caused a lot of damage to the render/plaster on an adjacent, lounge wall before it became obvious something was wrong!

So I’m now in a bit of a dilemma & would like some additional thoughts/advice from CH Engineers/tradesmen; should I drain the system down again & fit the new valve or just leave the blanking plug in place, top up with inhibitor & forget it?

Leave it as is , when Hugh did his C+G people were fitting gas heating without safety valves. Fitting them on the few solid fuel ones. That was the company I worked for, and most others.