New Timer Installed: One Zone Has Lower Pressure Than Manual Operation

Why Automated Valve Pressure Is Lower Than Manual Operation

After replacing a timer, one zone has noticeably lower pressure when run automatically vs. manually at the valve. No prior pressure issues.

Normal Behavior: Solenoid Opens ~85%

When a valve opens via solenoid, it typically opens to about 85% of full flow. Manual bleed opens it 100%. A small pressure difference is normal.

But If the Drop Is Severe...

• Old valve – Diaphragm or spring may be weak, preventing full opening.
• Flow control set too low – Adjust per standard procedure (open fully, close fully, open halfway).
• Debris in valve ports – Restricts flow even when solenoid is energized.

Recommendation

If the valve is old, replace it. The cost is low vs. ongoing frustration. Adjust flow control first; if no improvement, replace.