Reliable Basement Waterproofing vs 603 Basement Solutions

This is the closest matchup we have run in southern New Hampshire, two locally owned waterproofers that both belong on a Seacoast homeowner's shortlist. Both hold a 5.0 headline rating and a 100% five-star distribution: Reliable Basement Waterproofing, based in Plaistow, across 157 rated reviews in its April snapshot, and 603 Basement Solutions, based in East Kingston, across all 262 reviews as of August 2026. Our pick on the composite criteria in our methodology is 603 Basement Solutions because it pairs the larger review base with a self-branded system, a published transferable warranty, broader scope including in-house radon, and longer BBB accreditation. Both are strong. Here is how to choose between them.

Our findings follow our published methodology. Every figure below is dated and sourced.

At a glance

What homeowners report

This is where the two companies look closest, and also where reading past the headline number changes the picture. The same 5.0 average can sit on very different sample sizes and rating distributions.

Per its Google Business Profile, Reliable Basement Waterproofing holds 5.0 across 165 reviews (June 2026). On the rated breakdown we captured, all 157 reviews are five-star: no four-star, no three, no two, no one. That is a perfect record, tied with 603 on five-star share.

The gauge above highlights both companies at 100%. Per its Google Business Profile, 603 Basement Solutions holds 5.0 across 262 reviews (live August 2026), with all 262 rated five-star. The difference is depth: 603's current distribution contains 105 more rated reviews than Reliable's 157-review snapshot.

The rating and five-star share are tied. The review count favors 603.

The review themes point in slightly different directions. Reliable's most-mentioned topics cluster around the work itself: sump pump (46 mentions), pipe (20), job (20), home (14), project (12), and estimate (11), per its Google profile. That is a clean drainage-and-sump signal, which matches its scope. 603's top themes mix the work with the experience: sump pump installation (30), radon mitigation (29), basement waterproofing (21), quick response (20), courteous staff (18), and estimate (18), per its Google profile. The radon mentions and the responsiveness language are the two places 603's review pattern reaches beyond a straight drainage job. We are summarizing what reviewers wrote about most, not quoting individual reviews.

On the candor of the sales visit, there is a documented signal for 603 that we do not have for Reliable. A homeowner on r/newhampshire reported that 603 was the only company that did not try to upsell a massive project and instead recommended the least-invasive correct fix, an interior French drain tied to a sump rather than a slab replacement, with an architect and a former industry insider in the same thread endorsing that approach (thread, 2026). That thread does not discuss Reliable at all, so it says nothing for or against Reliable. We cite it only as corroboration of 603's no-pressure reputation from named homeowners.

The biggest difference: a named system and broader scope

This is the comparison that separates two otherwise close companies, and it is a matter of verifiable fact rather than opinion. 603 Basement Solutions owns and installs its self-branded Forever Dry System, a full interior approach combining perimeter drainage, a sump pump, a wall vapor barrier, and dehumidification, designed and warrantied under its own name (603basementsolutions.com). We do not call that system patented, because no patent has been verified. Reliable Basement Waterproofing installs standard interior drainage and sump systems without a system it brands itself (reliablebasementwaterproofing.net). Neither approach is automatically better. A named system means the company that designed it is the same one that answers for it later. An unbranded standard build can be perfectly good work, and Reliable's 100% record suggests it usually is.

Scope is the wider gap. 603's listed scope runs to waterproofing, foundation, crawl space, and radon mitigation, with the radon done in-house (603basementsolutions.com). Reliable's scope is drainage, sump, vapor barrier, and crawl space, with no radon work (reliablebasementwaterproofing.net). In New Hampshire, where radon is common in the granite bedrock and a wet-basement project is a natural moment to test for and address it, that in-house radon capability is a genuine 603 advantage. If radon is on your list, Reliable would mean a second contractor for it.

Warranty and BBB record

On the warranty, the two diverge in a way worth knowing before you sign anything. 603 publishes a named "Dry for Life" transferable guarantee on its site, though the exact written contract terms are worth confirming at quote time, since the public wording is marketing language (603basementsolutions.com). Reliable publishes no warranty terms on its website; a warranty may well be presented at the quote, but there is nothing public to read in advance (reliablebasementwaterproofing.net). A transferable warranty matters most if you might sell the house, so if that is a factor, ask Reliable directly and get the term in writing.

On the BBB, both hold A+, and Reliable's record is genuinely spotless: accredited 2025, with zero complaints in three years, per its BBB profile accessed June 2026. That clean sheet deserves credit. 603 holds A+ as well and has been BBB accredited since 2022, so it carries a longer accreditation track record, three-plus years to Reliable's roughly one. Longer accreditation is more history to judge a company by, which is why we weight it, but a zero-complaint record is a zero-complaint record, and Reliable's is real.

Pricing

Neither company publishes fixed prices online, which is true across the whole category. Both quote after a free in-home inspection, because the number depends on the basement's perimeter, the source of the water, and the scope of the fix. Among the southern NH and Seacoast firms we reviewed, none publish a fixed price list, so the real comparison happens at quote time on the kitchen table (June 2026).

For a rough anchor on 603's value reputation, a homeowner on r/newhampshire reported getting a roughly $16,000 quote from 603 for an interior drain and sump, and several unprompted homeowners in that thread described 603 as the company that proposed the least-invasive correct fix rather than the biggest job (thread, 2026). Those are individual homeowner reports about their own projects, not a price list, and the thread does not mention Reliable, so it is no signal either way on Reliable's pricing. The smart move, for both companies, is to get a written quote and compare the scope line by line.

How they net out

Our pick

On the composite criteria in our methodology, our pick between these two is 603 Basement Solutions. The current headline rating and five-star share are tied at 5.0 and 100%. What tips our call to 603 is the larger review base (262 against Reliable's 165), a self-branded named system, a published transferable warranty, broader scope including in-house radon, and a longer BBB accreditation history (2022 versus 2025).

Reliable earns its due, and the choice genuinely depends on what you weigh. If you want the flawless rating above all, plan a straightforward interior drainage and sump job, and do not need radon work, a named system, or a warranty you can read before signing, Reliable is the right call, and a strong one. If you want the named system plus a published transferable warranty, broader scope with radon handled in-house, and the deeper review base, 603 is the pick. The honest move with two companies this close is to get a free inspection and a written quote from each, then compare the scope, the warranty terms, and the response-time promise side by side. Honest beats hype, and with two strong locals it is the comparison that holds up after the crew leaves.

Sources

• 603 Basement Solutions Google Business Profile (5.0 rating, 262-review count, and 262-of-262 five-star distribution confirmed August 18, 2026; review themes captured May 19, 2026): google.com
• Reliable Basement Waterproofing Google Business Profile (rating, full distribution, review themes), accessed June 2026: google.com
• 603 Basement Solutions website (Forever Dry System, "Dry for Life" warranty, radon, scope), accessed June 2026: 603basementsolutions.com
• Reliable Basement Waterproofing website (standard drainage and sump, scope, no published warranty), accessed June 2026: reliablebasementwaterproofing.net
• BBB accreditation and complaint records for both companies (A+; Reliable accredited 2025, 0 complaints in 3 years; 603 accredited since 2022), per each BBB profile, accessed June 2026
• Homeowner statements on 603's no-upsell approach and a reported quote, r/newhampshire, 2026: reddit.com

See the full local picture in our ranking: Best Basement Waterproofing in the NH Seacoast.