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. Reliable Basement Waterproofing rates higher, and we will say that plainly up front: Reliable Basement Waterproofing, based in Plaistow, holds a perfect 5.0 on Google across 165 reviews, with a flawless 100% five-star share on the 157 rated reviews we recorded, and a spotless BBB record (A+, accredited 2025, zero complaints in three years). 603 Basement Solutions, based in East Kingston, holds 4.9 across 250 reviews, with a 97.6% five-star share on 249 rated reviews. So if you weigh the star average above everything else, Reliable wins it. Our pick on the composite criteria in our methodology is still 603 Basement Solutions, for reasons we lay out below: a self-branded named system where Reliable has none, a published transferable warranty where Reliable publishes none, broader scope including in-house radon, a larger and deeper review base, and longer BBB accreditation. Both are strong. The honest framing is two good picks, and 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. We read the full Google rating distribution for both, not just the star average, because a 5.0 and a 4.9 can describe very different sample sizes.

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, and we are not going to spin it as anything less. A 100% five-star share is the cleanest distribution in this entire local set, and it is a real point in Reliable's favor.

The gauge above highlights Reliable, because its five-star share is higher. Here is the nuance that the gauge cannot show. Per its Google Business Profile, 603 Basement Solutions holds 4.9 across 250 reviews (live June 2026), and on the rated breakdown it shows 243 five-star out of 249, with 3 four-star, 1 two-star, and 2 one-star. That is 97.6% five-star. The gap to Reliable's 100% is the six non-five-star reviews 603 has collected across a base that is more than half again as large. Our methodology treats a near-perfect score on a deep base as stronger evidence than a perfect score on a shallower one, because a single weak job, or a single difficult customer, can keep a 100% record intact only until it doesn't, and a larger sample has already absorbed more of those tests. 603's 249 rated reviews include 92 more rated reviews than Reliable's 157. A 97.6% that holds up across that many jobs is, by our reading, the sturdier signal, even though it is not the higher number.

To be clear, that is a reading of how we weight evidence, not a claim that 603 is rated higher. It is not. If a flawless star line is the single thing you care about, Reliable has it.

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. To be exact about what that is and is not: it is not a claim that 603 is the higher-rated company. It is not. Reliable Basement Waterproofing carries a perfect 5.0 and a flawless 100% five-star record, and 603's 4.9 and 97.6% sit just below it. What tips our composite call to 603 is everything around the star line: a self-branded named system where Reliable has none, a published transferable warranty where Reliable publishes none, broader scope including in-house radon, a larger and deeper review base (250 reviews and 249 rated, against Reliable's 165 and 157), and a longer BBB accreditation history (2022 versus 2025). On our reading, a 97.6% five-star share that holds across a base that size is a stronger signal than a perfect score on a smaller one.

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 (rating, full distribution, review themes), accessed June 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.