Buried inside Paragraph 7A of the current One to Four Family Residential Contract (TREC No. 20-19) is a single sentence with an outsized effect on older-home deals: "Any hydrostatic testing must be separately authorized by Seller in writing." A buyer can't just have an inspector open a cleanout and pressure-test the sewer line — the base contract flatly requires a separate written authorization before that happens. The Addendum for Authorizing Hydrostatic Testing (TREC No. 48-1) is that separate writing, and it does two jobs on one page: it gives the buyer permission to test, and it decides in advance who pays if the test causes damage.
What a hydrostatic test is, and why the contract singles it out
A hydrostatic test fills a plumbing or sewer line with water under pressure to check for leaks — useful on older homes with clay or cast-iron sewer lines that a standard visual inspection can't evaluate. It's also the one inspection method that can itself cause the damage it's checking for: pressurizing an already-compromised line can crack it further or force a backup. That's the reason the base contract treats it differently from a routine inspection and requires the seller's written sign-off before it happens at all, rather than folding it into the general inspection-access language in Paragraph 7A.
Paragraph A — the authorization
The form's own language: "Seller authorizes Buyer, at Buyer's expense, to engage a licensed plumber to perform a hydrostatic plumbing test on the Property." Two details worth flagging to a client: the buyer pays for the test itself regardless of which liability box gets checked in Paragraph B, and the person doing the testing must be a licensed plumber — TREC has separately confirmed that a general home inspector is not authorized to perform a hydrostatic test, even one licensed and permitted to make other inspections under the contract.
Paragraph B — who pays if the test causes damage
This is the paragraph that actually gets negotiated. The form gives the parties exactly three boxes, and the addendum isn't complete without one of them checked:
- (1) Seller shall be liable for damages caused by the hydrostatic plumbing test.
- (2) Buyer shall be liable for damages caused by the hydrostatic plumbing test.
- (3) Buyer shall be liable for damages caused by the hydrostatic plumbing test, capped at a dollar amount the parties fill in — "in an amount not to exceed $______________________."
There's no default and no split-the-difference option built into the form. Whoever accepts liability under (1) or (2) is on the hook for the full cost of any damage the test causes, and option (3) is the only place a dollar ceiling exists — and only for the buyer's side, not the seller's.
Mandatory form, situational trigger
The header on the printed form reads "PROMULGATED BY THE TEXAS REAL ESTATE COMMISSION (TREC)," not the "approved for voluntary use" language that appears on forms like the Non-Realty Items Addendum. TREC's own rule adopting the form describes it as approved for mandatory use as an addendum to be added to promulgated forms if the parties agree to hydrostatic testing — so it isn't optional paperwork once a hydrostatic test is on the table, but it also isn't a form every file needs. It only comes into play when a buyer actually wants the test performed.
Why this comes up: older homes and option-period leverage
This addendum shows up almost exclusively on resale homes with cast-iron or clay sewer lines old enough that root intrusion or corrosion is a live risk — which in practice means most pre-1980s Texas housing stock. It's a common option-period negotiation: a buyer's inspector flags an aging sewer line, the buyer wants a hydrostatic test before committing further, and the two sides have to agree not just to the test itself but to who eats the cost if the test cracks an already-fragile line. Because the base contract requires the seller's written authorization before any hydrostatic testing happens, this addendum — and specifically which Paragraph B box gets checked — is often the actual point of negotiation, not just a formality layered on top of an already-agreed test.