Relief Valves Or Expansion Tanks?

A colleague of mine was working out the math of having an expansion tank installed on his H2O heater. “A pair hundred bucks for the first install, as well as then I’ll probably accept to beat out out every bit much a dyad years downwardly the job,” he concluded.

This had me researching the whole subject of expansion tanks – Why are expansion tanks recommended for H2O heaters? What happens if you haven’t got 1? Could you lot install it yourself? Are in that location whatsoever alternatives to an expansion tank?

It appears that, at least every bit far as code requirements get, you lot need to take some sort of a thermal expansion device installed.

But what does an expansion tank (or any other thermal expansion device) actually do? What is a thermal expansion relief valve, anyway? And, what’sec the difference betwixt expansion tanks too relief valves, inwards price of toll as well as safe?

For answers to these as well as more questions, plunge correct inward!

Widely used plumbing codes such every bit IRC as well as UPC take the installation of a means of controlling thermal expansion caused by the increased pressure of hot H2O in unopen-loop, domestic plumbing, past using approved devices like thermal expansion tanks too thermal expansion relief valves.

Is Water Heater Thermal Expansion a Big Deal?

In a discussion… Yes.

As you lot power call up from high schoolhouse, H2O expands when heated. And, different air, H2O can’t be compressed, and so the expanded H2O needs extra infinite. If your storage H2O heater is already full to capacity, the expanding hot H2O needs to find somewhere else to become.

Until recently, this wasn’t an upshot… hot H2O merely expanded dorsum from a family water heater into the municipal provide pipes. 

Today, withal, about towns together with cities involve that ‘cheque valves’ be installed to forestall back-menses that could potentially contaminate the town H2O furnish. In more or less areas, civic government install a ‘pressure level regulating valve’ at family inlets to regulate water pressure level between xl and eighty psi.

Whether you accept a bank check valve or a pressure level regulating valve installed on your water inlet, it effectively prevents back-menstruum. In other words, the water in your house plumbing forms a unopen loop, in addition to has no mode dorsum into the civic furnish pipes. 

As hot H2O expands, it exerts pressure level on the water heater tank, and on your expensive pipes, bathroom fittings, too solenoid switches. (You tin find these on your washing motorcar together with dishwasher.) The resulting clothing together with tear tin can be quite costly, requiring these parts to be replaced inwards half their common life-bridge.

In addition, pressure inside your water heater leads the T&P relief valve to drip constantly… over fourth dimension, this could effort the valve to clog from scale make-upward, turning your water heater into a potential explosive. (Learn how to avoid having your H2O heater’sec lines clogged up with this tardily, pace-past-footstep lead on descaling.)

Expansion Tank vs. Thermal Expansion Relief Valve

Alright, and so right away you know that thermal expansion tin can’t be ignored. So, what’s the solution?

ane. Expansion Tank

Well, traditionally, the expansion tank has been the reply to thermal expansion. This pocket-size, metal container resembling a propane tank is typically installed on the water heater’s cold water inlet. For near thirty-, 40- or l-gallon H2O heaters, a two-gallon expansion tank is adequate, since H2O expands by some four% when heated to boiling (212 °F), thence, near 2% when heated from 59 °F through to 120 °F.

An expansion tank’sec lower one-half is filled with air (typically at 12 psi pressure level), piece a prophylactic bladder installed partway through the tank allows water coming inward through the peak to force down on the air below (run across image below). Hot water expanding from the water heater can therefore safely occupy the peak sleeping room of an expansion tank, until force per unit area is relieved by turning on a hot H2O faucet.

ii. Thermal Expansion Relief Valve (TERV)

A Thermal Expansion Relief Valve is typically a combination ball valve amongst a depression-force per unit area, spring-loaded prophylactic valve. The prophylactic valve opens (normally at pressures from 100 to 125 psi) to liberate hot water expanding out of a H2O heater, while the ball valve is a code-approved, manual close-off.

TERVs for domestic plumbing are typically calibrated to eject water which has attained pressures betwixt 100 and 125 psi. Note that this is much lower than the 150 psi setting at which a H2O heater’sec PRV is calibrated to open up up and allow out excess pressure. Therefore, the TERV acts equally the outset degree of safety, preventing pressure from building upward beyond 125 psi.

When hot water expands from the H2O heater, the pressure inward the pipage leading to the TERV builds upwards to the level that the valve is calibrated for, enjoin, 100 psi. At this betoken, the spring-loaded valve is pushed open up, ejecting the hot water into an outlet pipage that is typically a few feet long, leading to a drain where the H2O tin can safely menses out.

Pros too Cons of Expansion Tanks together with TERVs

As y'all’ve already guessed, both expansion tanks and TERVs come up with their own advantages as well as disadvantages. For starters, installing an expansion tank tin price more than twice equally much as installing a TERV, together with requires a fair amount of DIY skill or a professional person plumber for proper installation. 

In add-on, it is difficult to identify a malfunctioning expansion tank. Malfunctions may come about due to a host of reasons, including:

Plumbing Leaks

Expansion tanks oftentimes educate leaks owing to rusted connectors or pipage at the tank inlet. As a effect, the tank may fail and call for to be replaced within a few years, particularly inwards areas amongst difficult water.

Surface Condensation

Due to the hot water flowing into the expansion tank, significant amounts of condensation tin class on its surface. In add-on, the tank’s shut proximity to the water heater can add to the job, since the air surrounding the heater too tends to live excessively hot in addition to humid, encouraging condensation to grade. Over time, this leads to corrosion together with rust formation, resulting inwards leaks. 

Improper Installation

Experts recommend that an expansion tank should ever be installed vertically, alongside the H2O heater inlet at the superlative of the tank. In improver, to safeguard the installation against excessive vibration, for instance, from the surging pressure level of the hot water within the plumbing, it is recommended that the tank live secured to a wall alongside straps.

However, due to infinite constraints, for example, because the water heater is installed inwards a cupboard or crawl space, an expansion tank may be installed horizontally or upside downwards. This tin can crusade a tank to malfunction, past forming a hydronic air-lock*, as well as fifty-fifty significantly shorten its life-bridge.

*Note: A hydronic air-lock inside an expansion tank occurs when a steal of air is trapped below the H2O, typically inwards cases where the tank has been installed upside downward, such that incoming water enters the tank from the bottom instead of the peak. This may movement the expansion tank to neglect.

Rubber Bladder Pinhole Leaks

These are the nigh difficult to find, simply oftentimes drive the expansion tank to neglect, since the bladder is unable to proceed the water in addition to air separate. In such cases, the tank has to be replaced.

Low Air Pressure

Over time, the air pressure inside the lower bedroom of the expansion tank tin fall well below the required level of 12 psi. This can live corrected by but pumping inwards air using a bike ticker (or elementary air ticker). In about cases, air pressure level within the expansion tank might rest depression because the installer forgot to pump inward air during the installation!

However, the job tin can live hard to diagnose, requiring time together with endeavour, too multiple rounds of testing.

By comparing, a TERV tin live installed fairly rapidly, as well as requires lilliputian to no maintenance. The blueprint of a TERV is geared for industrial function, oft inwards outdoor and remote locations where regular scrutiny is impossible. Therefore, these condom valves are unremarkably rugged too capable of operation under adverse atmospheric condition.

However, the TERV has i major drawback – it releases excess force per unit area by allowing expanding hot water to operate off into a drain through the outlet piping, thereby encouraging wastage of water. (Of course, in a house, it is possible to minimize this wastage by just placing a pail or bucket below the outlet pipe, as well as utilizing the drip inward the garden or for other utilities.)

The handy table below sums up the pros in addition to cons of expansion tanks as well every bit TERVs. You tin can select the device that meliorate suits your domicile ready-upwards, later running an middle over the summary:

	Expansion Tank	Thermal Expansion Relief Valve (TERV)
Installation Cost	High (> $100)	Low (< $75)
Time to Install	Long (thirty – hr)	Short (ten – xxx minutes)
Ease of Operation	Easy	Easy
Eco-ingredient	Eco-friendly	Potential Water Wastage
Maintenance	High	Low
Expected Life-span	Short (two – half-dozen years)	Long (10+ years)

There… you lot directly take all the facts you need, and tin can make up one's mind for yourself whether you lot require a thermal expansion device installed in your domicile. What’s more than, you can choose whichever 1 is better for your needs!