Electric shower Pressure relief device has burstwhat to check
Water from the small tube under the shower means a one-shot safety part has ruptured. Replacing it without finding the blockage just bursts the next one.
Take care
What this means
The pressure relief device is the part of an electric shower that nobody knows exists until it fails, and understanding what it is for makes the repair obvious. The unit takes cold mains water, heats it and sends it out through a hose and a showerhead. If that outlet blocks — a scaled spray plate, a kinked hose, a head left with the flow restrictor in — the water has nowhere to go, but the elements are still adding heat and the mains is still pushing. Pressure rises inside a plastic assembly very quickly. So manufacturers fit a deliberately weak point that ruptures at a set pressure and dumps the water out of a stub under the case, sacrificing a cheap part to save the tank and the fittings.
Two things follow from that and both are on this page. The first is that a burst device is a symptom, never the disease. It ruptured because something downstream of it blocked, and Triton say so in a note printed under their own fault table: identify the cause before fitting a new one.
Fit a replacement to a shower that still has a scaled head and you will be fitting another shortly. The second is that these are one-shot parts. There is nothing to reset, nothing that reseals when it cools, and no way to run the shower in the meantime — until it is replaced, the water will keep coming out of the relief stub instead of the showerhead. Triton add a detail that catches people out: after fitting a new device the unit has to be commissioned again, with the showerhead removed, because commissioning it against a fitted head is one of the documented ways to burst the new one immediately.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Blocked or scaled showerhead | Named first by every manufacturer here. A spray plate furred up with scale is the classic outlet restriction and the classic reason these burst. | Common |
| Kinked or blocked hose | A hose twisted behind the riser rail, or one whose liner has collapsed internally. The outside can look perfect while the bore is shut. | Common |
| Commissioned with the showerhead fitted | Triton document this specifically. Purging a new installation against a fitted head is enough to rupture the device before the shower is ever used. | Occasional |
| Non-standard or restrictive showerhead | A head not intended for an electric shower, or one with an eco restrictor, cuts the outlet area enough to raise pressure past the design point. | Occasional |
What to try yourself
Pull the cord and isolate the shower before doing anything else, then close the servicing valve on the inlet so it stops discharging.
The water coming from the relief stub can be hot. Let it run cold or let the unit stand before you work on it.Find the blockage before you order anything. Take the head off and hold it to the light, and run water through the hose on its own to see whether it passes freely.
Descale or replace the showerhead, and replace the hose if it does not flow freely with the head off. Both are inexpensive and both are the usual answer.
Check the head is one intended for an electric shower. Anything with a restrictor, or a rain head meant for a mixer, puts these units outside what they were designed against.
Have the relief device replaced, and make sure whoever fits it commissions the unit afterwards with the showerhead off. Triton print that step for a reason.
Get a qualified electrician to look at your electric shower
We do not pass enquiries to a repair firm, so there is no form here. When you book a qualified electrician, tell them the make, the model and the exact code or message on the display, and ask whether they carry parts for this make — that is what turns one visit into a repair rather than a quote.
What it costs to fix
Typical repair cost
£20–£150
Time on site
40 minutes
The device itself is inexpensive. The cost is the visit and the commissioning afterwards, plus a new head or hose if that is what burst it, which it usually is.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Own this appliance and had this code? . Nothing is published until a person has read it.
Related electric shower fault codes
- Water leaking from the shower unitGet it checkedWater escaping from the casing rather than the head puts mains water inside a live appliance. Manufacturers say stop using it, and that is the right answer.Related: leaking
- Shower runs coldGet it checkedWater flows but never heats. On an electric shower this is nearly always the supply, the flow through it, or an element that has stopped working.Related: same brand
- Shower keeps tripping the electricsStop — call an engineerA shower that trips the breaker or RCD is reporting a real electrical fault. Do not keep resetting it to get one more shower out of it.Related: same brand
- Shower completely deadGet it checkedNo neon, no water, nothing when you pull the cord. On an electric shower a total dead is almost always the supply rather than the appliance.Related: same brand
- Thermal cut-out has operatedGet it checkedThe safety device has taken the elements out of circuit. Whether you can reset it yourself depends entirely on the brand, and the answers differ.Related: same brand
- Water suddenly scaldingGet it checkedAn electric shower that runs too hot is usually short of flow rather than making too much heat. The exception is a thermostatic model, which should not do this at all.Related: same brand
Related guides
Common questions
Can the pressure relief device be reset?
No. It is a one-shot part — it ruptures and stays ruptured. Anything that suggests resetting it is describing a different component, most likely the thermal cut-out.
Can I use the shower until it is fixed?
Not usefully. With the device burst, water takes the easy route out of the relief stub rather than through the head, so you get little or no flow where you want it and water where you do not.
Why did it go when nothing changed?
Because the usual cause is gradual. Scale builds in the showerhead over months, the outlet narrows a little at a time, and one day the pressure crosses the threshold. Nothing changed on the day it burst.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.