Essentra

Essentra heat-resistant sealing parts for hot tub heaters

Sealing components are small, inexpensive and almost always the reason a heater assembly starts to weep. The Essentra range listed here concentrates on exactly that point in the circuit: the joint between a heating element and its housing, where water sits under pressure and at the highest temperature anywhere in the system. Here you will find the 13/18 mm heat-resistant O-ring for hot tub heater elements, article PPS-10120, a replacement part for the element seal in flow-through spa heaters.

Què cobreix el rang

The focus is narrow by design. Rather than a general assortment of rubber rings, this is a sealing part specified for the thermal load around a heating element, where an ordinary cold-water O-ring tends to harden, flatten and lose its ability to spring back against the sealing face.

• Dimensions: 13 mm inner diameter and 18 mm outer diameter, which gives a cord thickness of 2.5 mm.
• Aplicació: heater element seals in hot tub and spa heating assemblies.
• Número d'article: PPS-10120, useful when cross-checking against a parts list or an exploded view.
• Type of part: a wear item, intended to be renewed whenever the heater is opened rather than refitted.

Where the element seal sits in a spa heater

In most hot tub heaters, water is pushed through a tube or chamber in which one or more heating elements are mounted. Each element passes through the wall of that chamber and is held by a nut, flange or threaded boss, and an O-ring forms the watertight barrier at that crossing. The ring is squeezed into a groove or against a shoulder, and once compressed it has to stay elastic while being heated and cooled every time the heater cycles.

Because this joint is close to the element itself, it experiences far more thermal cycling than seals in the pump or filter circuit. That is why element rings age faster than the unions and lid gaskets elsewhere on the same spa, and why many service visits end with nothing more than a fresh ring and a cleaned sealing face.

Measuring and identifying the right ring

O-rings are specified by inner diameter and cord thickness, and the outer diameter follows from the two. Before ordering, it is worth taking three readings from the old part rather than guessing from the size of the opening.

• Diàmetre interior: measure across the hole with the ring laid flat and relaxed, not stretched. A ring that has been fitted for years may have taken a set and read slightly large.
• Cord thickness: measure the cross-section of the rubber itself. A 2.5 mm cord is noticeably slimmer than the 3 mm and 3.5 mm sections used in many pump and union seals.
• Diàmetre exterior: inner diameter plus twice the cord thickness — 13 mm plus 5 mm gives 18 mm here, which is a quick way to confirm you are looking at the same size.
• Groove and seat: check that the old ring came from a groove rather than being trapped flat between two faces, since a flat gasket cannot be substituted by an O-ring and vice versa.
• Exploded view: if the heater came with a diagram, note the position number of the seal and count how many rings the assembly uses; elements are often fitted in pairs or threes.

A ring that has flattened into an oval cross-section, cracked at the inner edge, gone chalky or hard, or that no longer springs back when pinched should be measured with care — compare it against the housing groove as well, because a badly deformed ring will under-read.

Signs the seal needs renewing

Slow seepage around the heater body, mineral staining or white crusting below the element nut, and damp insulation in the equipment bay all point at the element seal rather than at a cracked housing. Water tracking along the element and reaching the terminals is the reason this part is worth replacing early. When refitting, clean the groove and the sealing face of old scale, fit the ring dry or with a silicone-based lubricant suitable for rubber seals, and tighten evenly so the ring is compressed rather than pinched or rolled.

Essentra at PoolParthub.com

Here we list the Essentra heat-resistant element O-ring in 13/18 mm with its PoolParthub article number, so the size can be matched against a measured part or a parts list before ordering. It is the kind of component that is easiest to buy as a set alongside the other seals in the heater, so that everything opened during a service goes back together with new rubber.

Sealing parts are grouped on the site by dimension and by application, which makes it straightforward to compare a 2.5 mm cord ring against neighbouring sizes if a measurement falls between two options. Customers across Europe order these small parts together with heater elements, pressure switches and unions, keeping a complete heater repair to a single order.