Galvanised fittings: threads, unions and a proper seal

"I've remade the fitting three times and it still weeps." When you bring it to me, I look at it and always find one of these things: dirty thread, too much hemp, too little hemp, or a union tightened with the wrong wrench. The galvanised fitting is a simple part, but it forgives very little.

Reading the abbreviations

In the collection you will find sockets, nipples, reducers, elbows, tees, crosses, plugs and unions. There are only a few abbreviations to know:

• M is the male thread, external; F is the female, internal. An MF elbow has a male end and a female end.
• Reducing means the two ends have different sizes.
• The size in inches indicates the gas thread of the pipe, not the outside diameter that you measure with callipers. That is why a 1/2" pipe measures on the outside more than a centimetre and a half.

When you need the union

A run of threaded pipes and fittings is assembled by screwing in one direction only. If you are closing a loop or have to fit a piece between two pipes that are already fixed, you cannot screw it in from both sides: you need the union, which opens and closes without turning the pipes. Put one near pumps, filters and valves as well, which will have to be removed one day.

The flat-seat union seals with a gasket: it must be tightened just right and the gasket is replaced whenever you reopen it. The conical-seat one seals metal on metal: no gasket, but the seats must be clean and unmarked.

Sealing the thread

The classic method is hemp and paste: clean thread, hemp wound in the direction of tightening, thin and even, paste on top. If you overdo the hemp the fitting does not go in far enough and weeps; if there is too little, it does not seal. As an alternative you can use synthetic thread-sealing tapes and cords, each with its own instructions for use: follow those of the product you use.

A threaded fitting is never backed off to align it. If you have gone past, take it apart and redo the seal.

Galvanised, copper and brass together

This is where the damage I see years later is done. In water lines, copper must not be put upstream of galvanised: the copper ions carried by the water attack the galvanising and the pipe is perforated from the inside. Between different metals, brass acts as the transition fitting, and that is why in the collection you will also find brass sockets, nipples and elbows.

Gas: dedicated fittings and valves

In the collection there are also valves, flexible hoses, fittings and control units for natural gas and LPG. These are dedicated components, and a gas installation is built and certified by a qualified installer: we supply the parts that he specifies, with the right size and type of connection.

What I need to know

• Thread size in inches and whether they are male or female.
• What fluid is passing: water, air, gas, and the working pressure.
• Material of the existing pipes upstream and downstream.
• For gas: the list of components specified by the installer.
• Quantity: single piece or supply for an installation.

We stock these

A few items from the range we keep. If you cannot find the size or the model you need, just ask: what you see online is only part of what we can source for you.

Galvanised fittings UNIONS MF ART.331 - 1'1/2A.M.E.S. srl Galvanised fittings UNIONS FF ART.340A.M.E.S. srl Galvanised fittings UNIONS FF ART.330A.M.E.S. srl Galvanised fittings 90° reducing tees art.130RA.M.E.S. srl Galvanised fittings TEE 90 DEGREES ART.130A.M.E.S. srl Galvanised fittings Reducing nipplesA.M.E.S. srl

Browse the whole category: Galvanised Fittings