Skip to content
English - United Kingdom
Go to www.mixergy.co.uk
  • There are no suggestions because the search field is empty.

Tundish discharging

Find which valve or setting is causing water to discharge at the tundish.

Start by working out whether the tundish is discharging all the time or only now and then.

SAFETY

Only work on unvented safety devices if you're competent in unvented hot water systems. Discharge of very hot water at the tundish can mean the cylinder is overheating, so treat it as urgent.

Discharging now and then

Intermittent discharge usually means the expansion relief valve is opening as the cylinder heats up.

1. Check the expansion vessel charge

Is the pre-charge pressure correct?

  • If not, re-pressurise the expansion vessel to the correct pressure and retest.
  • If yes, replace the expansion relief valve.

Discharging all the time

First, check whether the water at the tundish is cold, or warm to hot.

If the water is cold

1. Check the standing pressure

Is the standing pressure at the hot water outlet higher than the pressure reducing valve setting?

  • If yes, replace the pressure reducing valve.
  • If not, go to step 2.

2. Check the expansion relief valve

Is the expansion relief valve letting by?

  • If yes, clean or replace the expansion relief valve.
  • If not, go to step 3.

3. Check the TPRV

Is the temperature and pressure relief valve (TPRV) letting by?

  • If yes, clean or replace the TPRV.

If the water is warm or hot

1. Check the standing pressure

Is the standing pressure higher than the pressure reducing valve setting?

  • If yes, replace the pressure reducing valve.
  • If not, go to step 2.

2. Check the hot water temperature

Is the temperature at the hot water outlet higher than the TPRV setting (90 to 95°C)?

  • If yes, check and replace the cylinder thermostat or thermal cut-out.
  • If not, check and replace the TPRV.