LETTER OF TRANSMITTAL
                                      FOR
                   10 5/8% SENIOR SUBORDINATED NOTES DUE 2006
                                       OF
 
                                  AMTROL INC.
 
   THE EXCHANGE OFFER WILL EXPIRE AT 5:00 P.M., NEW YORK CITY TIME, ON
                                        , 1997
             (THE "EXPIRATION DATE") UNLESS EXTENDED BY AMTROL INC.
 
                                EXCHANGE AGENT:
                              THE BANK OF NEW YORK
 

                                                 
                     BY HAND:                                            BY MAIL:
               The Bank Of New York                        (INSURED OR REGISTERED RECOMMENDED)
              Reorganization Section                               The Bank Of New York
                101 Barclay Street                                Reorganization Section
                   Floor 7 East                                     101 Barclay Street
             New York, New York 10286                                  Floor 7 East
             Attention: Enrique Lopez                            New York, New York 10286
                                                                 Attention: Enrique Lopez
 
              BY OVERNIGHT EXPRESS:                                   BY FACSIMILE:
               The Bank Of New York                                   (212) 571-3080
              Reorganization Section                         (for Eligible Institutions Only)
                101 Barclay Street                                    BY TELEPHONE:
                   Floor 7 East                                       (212) 815-2742
             New York, New York 10286
             Attention: Enrique Lopez

 
    DELIVERY OF THIS LETTER OF TRANSMITTAL TO AN ADDRESS OTHER THAN AS SET FORTH
ABOVE OR TRANSMISSION OF INSTRUCTIONS VIA A FACSIMILE TRANSMISSION TO A NUMBER
OTHER THAN AS SET FORTH ABOVE WILL NOT CONSTITUTE A VALID DELIVERY.
 
    The undersigned acknowledges receipt of the Prospectus dated            ,
1997 (the "Prospectus") of AMTROL Inc. ("AMTROL"), and this Letter of
Transmittal (the "Letter of Transmittal"), which together describe AMTROL's
offer (the "Exchange Offer") to exchange $1,000 in principal amount of its new
10 5/8% Senior Subordinated Notes due 2006 (the "New Notes") to exchange $1,000
in principal amount of outstanding 10 5/8% Senior Subordinated Notes due 2006
(the "Notes"). The terms of the New Notes are identical in all material respects
(including principal amount, interest rate and maturity) to the terms of the
Notes for which they may be exchanged pursuant to the Exchange Offer, except
that the New Notes are freely transferable by holders thereof (except as
provided herein or in the Prospectus) and are not subject to any covenant
regarding registration under the Securities Act of 1933, as amended (the
"Securities Act").
 
    The undersigned has checked the appropriate boxes below and signed this
Letter of Transmittal to indicate the action the undersigned desires to take
with respect to the Exchange Offer.
 

        PLEASE READ THE ENTIRE LETTER OF TRANSMITTAL AND THE PROSPECTUS
                    CAREFULLY BEFORE CHECKING ANY BOX BELOW
 
YOUR BANK OR BROKER CAN ASSIST YOU IN COMPLETING THIS FORM. THE INSTRUCTIONS
INCLUDED WITH THIS LETTER OF TRANSMITTAL MUST BE FOLLOWED. QUESTIONS AND
REQUESTS FOR ASSISTANCE OR FOR ADDITIONAL COPIES OF THE PROSPECTUS AND THIS
LETTER OF TRANSMITTAL MAY BE DIRECTED TO THE EXCHANGE AGENT.
 
    List below the Notes to which this Letter of Transmittal relates. If the
space provided below is inadequate, the Certificate Numbers and Principal
Amounts should be listed on a separate signed schedule affixed hereto.

                                                                                   
                                  DESCRIPTION OF NOTES TENDERED HEREWITH
 

                                                                              AGGREGATE
                                                                              PRINCIPAL
                                                                                AMOUNT        PRINCIPAL
     NAME(S) AND ADDRESS(ES) OF REGISTERED HOLDER(S)         CERTIFICATE    REPRESENTED BY      AMOUNT
                     (PLEASE FILL IN)                        NUMBERS(S)*        NOTES*        TENDERED**
                                                                                   
 
                                                              TOTAL

 
*   Need not be completed by book-entry holders.
 
**  Unless otherwise indicated, the holder will be deemed to have tendered the
    full aggregate principal amount represented by such Notes. See instruction
    2.
 
    This Letter of Transmittal is to be used either if certificates of Notes are
to be forwarded herewith or if delivery of Notes is to be made by book-entry
transfer to an account maintained by the Exchange Agent at The Depository Trust
Company, pursuant to the procedures set forth in "The Exchange Offer--Procedures
for Tendering" in the Prospectus. Delivery of documents to the book-entry
transfer facility does not constitute delivery to the Exchange Agent.
 
    Holders whose Notes are not immediately available or who cannot deliver
their Notes and all other documents required hereby to the Exchange Agent on or
prior to the Expiration Date must tender their Notes according to the guaranteed
delivery procedure set forth in the Prospectus under the caption "The Exchange
Offer--Procedures for Tendering."
 
/ / CHECK HERE IF TENDERED NOTES ARE BEING DELIVERED BY BOOK-ENTRY TRANSFER MADE
    TO AN ACCOUNT MAINTAINED BY THE EXCHANGE AGENT WITH THE BOOK-ENTRY TRANSFER
    FACILITY AND COMPLETE THE FOLLOWING:
 
    Name of Tendering Institution
  ------------------------------------------------------------------------
 
/ / The Depository Trust Company
- ---------------------------------------------------------------------
 
    Account Number
  ------------------------------------------------------------------------------
 
    Transaction Code Number
  ----------------------------------------------------------------------------
 
/ / CHECK HERE IF TENDERED NOTES ARE BEING DELIVERED PURSUANT TO A NOTICE OF
    GUARANTEED DELIVERY AND COMPLETE THE FOLLOWING:
 
    Name of Registered Holder(s)
  -----------------------------------------------------------------------
 
    Name of Eligible Institution that Guaranteed Delivery
  ---------------------------------------------------
 
    Date of Execution of Notice of Guaranteed Delivery
  -----------------------------------------------------
 
    If Delivered by Book-Entry Transfer:
 
    Account Number
  ------------------------------------------------------------------------------

/ / CHECK HERE IF NEW NOTES ARE TO BE DELIVERED TO PERSON OTHER THAN PERSON
    SIGNING THE LETTER OF TRANSMITTAL:
 
    Name
  ------------------------------------------------------------------------------
 
                                  (Please Print)
 
    Address
  ------------------------------------------------------------------------------
 
                               (Including Zip Code)
 
/ / CHECK HERE IF NEW NOTES ARE TO BE DELIVERED TO AN ADDRESS DIFFERENT FROM
    THAT LISTED ELSEWHERE IN THIS LETTER OF TRANSMITTAL:
 
    Address
  ------------------------------------------------------------------------------
 
                               (Including Zip Code)
 
/ / CHECK HERE IF YOU ARE A BROKER-DEALER AND WISH TO RECEIVE 10 ADDITIONAL
    COPIES OF THE PROSPECTUS AND 10 COPIES OF ANY AMENDMENTS OR SUPPLEMENTS
    THERETO.
 
    Name:
  ------------------------------------------------------------------------------
 
    Address:
  ------------------------------------------------------------------------------
 
    If the undersigned is not a broker-dealer, the undersigned represents that
it is not engaged in, and does not intend to engage in, a distribution of New
Notes. If the undersigned is a broker-dealer that will receive New Notes for its
own account in exchange for Notes that were acquired as result of market-making
activities or other trading activities, it acknowledges that it will deliver a
prospectus in connection with any resale of such New Notes; however, by so
acknowledging and by delivering a prospectus, the undersigned will not be deemed
to admit that it is an "underwriter" within the meaning of the Securities Act.

              PLEASE READ THE ACCOMPANYING INSTRUCTIONS CAREFULLY
 
Ladies and Gentlemen:
 
    Upon the terms and subject to the conditions of the Exchange Offer, the
undersigned hereby tenders to AMTROL the above-described principal amount of the
Notes indicated above. Subject to, and effective upon, the acceptance for
exchange of the Notes tendered herewith, the undersigned hereby exchanges,
assigns and transfers to, or upon the order of, AMTROL all right, title and
interest in and to such Notes. The undersigned hereby irrevocably constitutes
and appoints the Exchange Agent the true and lawful agent and attorney-in-fact
of the undersigned (with full knowledge that said Exchange Agent acts as the
agent of AMTROL in connection with the Exchange Offer) to cause the Notes to be
assigned, transferred and exchanged. The undersigned represents and warrants
that it has full power and authority to tender, exchange, assign and transfer
the Notes and to acquire New Notes issuable upon the exchange of such tendered
Notes, and that, when the same are accepted for exchange, AMTROL will acquire
good and unencumbered title to the tendered Notes, free and clear of all liens,
restrictions, charges and encumbrances and not subject to any adverse claim. The
undersigned also warrants that it will, upon request, execute and deliver any
additional documents deemed by the Exchange Agent or AMTROL to be necessary or
desirable to complete the exchange, assignment and transfer of tendered Notes or
transfer ownership of such Notes on the account books maintained by the
book-entry transfer facility. The undersigned further agrees that acceptance of
any and all validly tendered Notes by AMTROL and the issuance of New Notes in
exchange therefor shall constitute performance in full by AMTROL of its
obligations under the Registration Agreement (as defined in the Prospectus) and
that AMTROL shall have no further obligations or liabilities thereunder except
as provided in the first paragraph of Section 3 of said agreement.
 
    The Exchange Offer is subject to certain conditions as set forth in the
Prospectus under the caption "The Exchange Offer--General." The undersigned
recognizes that as a result of these conditions (which may be waived, in whole
or in part, by AMTROL), as more particularly set forth in the Prospectus, AMTROL
may not be required to exchange any of the Notes tendered hereby and, in such
event, the Notes not exchanged will be returned to the undersigned at the
address shown above.
 
    By tendering, each holder of Notes represents that New Notes acquired in the
exchange will be obtained in the ordinary course of such holder's business, that
such holder has no arrangement with any person to participate in the
distribution of such New Notes, that such holder is not an "affiliate" of AMTROL
within the meaning of Rule 405 under the Securities Act and that such holder is
not engaged in, and does not intend to engage in, a distribution of the New
Notes. Any holder of Notes using the Exchange Offer to participate in a
distribution of the New Notes (i) cannot rely on the position of the staff of
the Securities and Exchange Commission (the "Commission") enunciated in its
interpretive letter with respect to Exxon Capital Holdings Corporation
(available April 13, 1989) or similar letters and (ii) must comply with the
registration and prospectus requirements of the Securities Act in connection
with a secondary resale transaction.
 
    If the undersigned is not a broker-dealer, the undersigned represents that
it is not engaged in, and does not intend to engage in, a distribution of New
Notes. If the undersigned is a broker-dealer that will receive New Notes for its
own account in exchange for Notes that were acquired as a result of
market-making activities or other trading as a result of market-making
activities or other trading activities, it acknowledges that it will deliver a
prospectus in connection with any resale of such New Notes; however, by so
acknowledging and by delivering a prospectus, the undersigned will not be deemed
to admit that it is an "underwriter" within the meaning of the Securities Act.
 
    All authority herein conferred or agreed to be conferred shall survive the
death or incapacity of the undersigned and every obligation of the undersigned
hereunder shall be binding upon the heirs, personal representatives, successors
and assigns of the undersigned. Tendered Notes may be withdrawn at any time
prior to the Expiration Date in accordance with the terms of the Letter of
Transmittal.
 
    Certificates for all New Notes delivered in exchange for tendered Notes and
any Notes delivered herewith but not exchanged, and registered in the name of
the undersigned, shall be delivered to the undersigned at the address shown
below the signature of the undersigned.

                         TENDERING HOLDER(S) SIGN HERE
                  (Complete accompanying substitute Form W-9)
 
- --------------------------------------------------------------------------------
 
- --------------------------------------------------------------------------------
                           SIGNATURE(S) OF HOLDER(S)
 
Dated ___________________    Area Code and Telephone Number: ___________________
 
(Must be signed by registered holder(s) exactly as name(s) appear(s) on
certificate(s) of Notes. If signature is by a trustee, executor, administrator,
guardian, attorney-in-fact, officer of a corporation or other person acting in a
fiduciary or representative capacity, please set forth the full title of such
person.) See Instruction 3.
 
Name(s) ________________________________________________________________________
 
- --------------------------------------------------------------------------------
                                 (PLEASE PRINT)
 
Capacity (full title) __________________________________________________________
 
Address ________________________________________________________________________
                              (INCLUDING ZIP CODE)
 
Area Code and Telephone No. ____________________________________________________
 
Taxpayer Identification No. ____________________________________________________
 
                           GUARANTEE OF SIGNATURE(S)
                        (IF REQUIRED--SEE INSTRUCTION 3)
 
Authorized Signature ___________________________________________________________
 
Name ___________________________________________________________________________
 
Title __________________________________________________________________________
 
Address ________________________________________________________________________
 
Name of Firm ___________________________________________________________________
 
Area Code and Telephone No. ____________________________________________________
 
Dated __________________________________________________________________________

                                  INSTRUCTIONS
 
         FORMING PART OF THE TERMS AND CONDITIONS OF THE EXCHANGE OFFER
 
1. DELIVERY OF THIS LETTER OF TRANSMITTAL AND CERTIFICATES.
 
    Certificates for all physically delivered Notes or confirmation of any
book-entry transfer to the Exchange Agent's or its agent's account at a
book-entry transfer facility of Notes tendered by book-entry transfer, as well
as a properly completed and duly executed copy of this Letter of Transmittal or
facsimile thereof, and any other documents required by this Letter of
Transmittal, must be received by the Exchange Agent at any of its addresses set
forth herein on or prior to the Expiration Date (as defined in the Prospectus).
 
    THE METHOD OF DELIVERY OF THIS LETTER OF TRANSMITTAL, THE NOTES AND ANY
OTHER REQUIRED DOCUMENTS IS AT THE ELECTION AND RISK OF THE HOLDER, AND EXCEPT
AS OTHERWISE PROVIDED BELOW, THE DELIVERY WILL BE DEEMED MADE ONLY WHEN ACTUALLY
RECEIVED OR CONFIRMED BY THE EXCHANGE AGENT. IF SUCH DELIVERY IS BY MAIL, IT IS
SUGGESTED THAT REGISTERED MAIL WITH RETURN RECEIPT REQUESTED, PROPERLY INSURED,
BE USED. IN ALL CASES SUFFICIENT TIME SHOULD BE ALLOWED TO PERMIT TIMELY
DELIVERY.
 
    Holders whose Notes are not immediately available or who cannot deliver
their Notes and all other required documents to the Exchange Agent on or prior
to the Expiration Date or comply with book-entry transfer procedures on a timely
basis must tender their Notes pursuant to the guaranteed delivery procedure set
forth in that Prospectus under "The Exchange Offer--Guaranteed Delivery
Procedures." Pursuant to such procedure: (i) such tender must be made by or
through an Eligible Institution (as defined in the Prospectus); (ii) prior to
the Expiration Date the Exchange Agent must have received from such Eligible
Institution a properly completed and duly executed Notice of Guaranteed Delivery
(by facsimile transmission, mail or hand delivery) setting forth the name and
address of the holder of the Notes, the certificate number or numbers of such
Notes and the prinicpal amount of Notes tendered, stating that the tender is
being made thereby, and guaranteeing that, within five business days after the
Expiration Date, the Letter of Transmittal (or facsimile thereof), together with
the certificate(s) representing the Notes to be tendered in proper form for
transfer and any other documents required by the Letter of Transmittal, will be
deposited by the Eligible Institution with the Exchange Agent; and (iii) all
tendered Notes (or a confirmation of any book-entry transfer of such Notes into
the Exchange Agent's account at a book-entry transfer facility) as well as this
Letter of Transmittal and all other documents required by this Letter of
Transmittal, must be received by the Exchange Agent within five business days
after the date of execution of such Notice of Guaranteed Delivery, all as
provided in the Prospectus under the caption "The Exchange Offer--Guaranteed
Delivery Procedures."
 
    No alternative, conditional, irregular or contingent tenders will be
accepted. All tendering holders, by execution of this Letter of Transmittal (or
facsimile thereof), shall waive any right to receive notice of the acceptance of
the Notes for exchange.
 
2. PARTIAL TENDERS; WITHDRAWALS.
 
    If less than the entire principal amount of Notes evidenced by a submitted
certificate is tendered, the tendering holder should fill in the principal
amount tendered in the box entitled "Principal Amount Tendered." A newly issued
certificate for the principal amount of Notes submitted but not tendered will be
sent to such holder as soon as practicable after the Expiration Date. All Notes
delivered to the Exchange Agent will be deemed to have been tendered unless
otherwise clearly indicated.
 
    Tenders of Notes pursuant to the Exchange Offer are irrevocable, except that
Notes tendered pursuant to the Exchange Offer may be withdrawn at any time prior
to 5:00 P.M. New York City time, on the Expiration Date. To be effective, a
letter notice or facsimile transmission notice of withdrawal must be received by
the Exchange Agent by 5:00 P.M., New York City time, on the Expiration Date
unless extended by AMTROL. Any such notice of withdrawal must specify the person
named in the Letter of Transmittal as having tendered Notes to be withdrawn, the
certificate numbers of the Notes to be withdrawn, the principal amount of Notes
delivered for exchange and a statement that such holder is withdrawing his or
her election to have such Notes exchanged, and must be signed by the holder in
the same manner as the originial signature on the Letter of Transmittal by which
such Notes were tendered (including any required signature guarantees) or be
accompanied by documents of transfer sufficient to permit the Trustee with
respect to the Notes to register the transfer of such Notes into the name of the
Depositor withdrawing the tender and must specify the name in which any such
Notes are to be registered, if different from that of the holder. The Exchange
Agent will return the properly withdrawn Notes promptly following receipt of
notice of withdrawal. If Notes have been tendered pursuant to the procedure for
book-entry transfer, any notice of withdrawal must specify the name and number
of the account at the book-entry transfer facility to be credited with the
withdrawn Notes or otherwise comply with the book-entry transfer facility's
procedures. All questions as to the validity of notices of withdrawals,
including time of receipt, will be determined by AMTROL, and such determination
will be final and binding on all parties.

3. SIGNATURE ON THIS LETTER OF TRANSMITTAL; WRITTEN INSTRUMENTS AND
  ENDORSEMENTS; GUARANTEE OF SIGNATURES.
 
    If this Letter of Transmittal is signed by the registered holder(s) of the
Notes tendered hereby, the signature must correspond with the name(s) as written
on the face of the certificates without alteration, enlargement or any change
whatsoever.
 
    If any of the Notes tendered hereby are owned of record by two or more joint
owners, all such owners must sign this Letter of Transmittal.
 
    If a number of Notes registered in different names are tendered, it will be
necessary to complete, sign and submit as many separate copies of this Letter of
Transmittal as there are different registrations of Notes.
 
    When this Letter of Transmittal is signed by the registered holder or
holders (which term, for the purposes described herein, shall include the
book-entry transfer facility whose name appears on a security listing as the
owner of the Notes) of Notes listed and tendered hereby, no endorsements of
certificates or separate written instruments of transfer or exchange are
required.
 
    If this Letter of Transmittal is signed by a person other than the
registered holder or holders of the Notes listed, such Notes must be endorsed or
accompanied by separate written instruments of transfer or exchange in form
satisfactory to AMTROL and duly executed by the registered holder, in either
case signed exactly as the name or names of the registered holder or holders
appear(s) on the Notes.
 
    If this Letter of Transmittal, any certificates or separate written
instruments of transfer or exchange are signed by trustees, executors,
administrators, guardians, attorneys-in-fact, officers of corporations or others
acting in a fiduciary or representative capacity, such persons should so
indicate when signing, and, unless waived by AMTROL, proper evidence
satisfactory to AMTROL of their authority so to act must be submitted.
 
    Endorsements on certificates or signatures on separate written instruments
of transfer or exchange required by this Instruction 3 must be guaranteed by an
Eligible Institution.
 
    Signatures on this Letter of Transmittal need not be guaranteed by an
Eligible Institution, provided the Notes are tendered (i) by a registered holder
of such Notes, for the holder of such Notes; or (ii) for the account of an
Eligible Institution.
 
4. TRANSFER TAXES.
 
    AMTROL shall pay all transfer taxes, if any, applicable to the transfer and
exchange of Notes to it or its order pursuant to the Exchange Offer. If a
transfer tax is imposed for any reason other than the transfer and exchange of
Notes to AMTROL or its order pursuant to the Exchange Offer, the amount of any
such transfer taxes (whether imposed on the registered holder or any other
person) will be payable by the tendering holder. If satisfactory evidence of
payment of such taxes or exception therefrom is not submitted herewith the
amount of such transfer taxes will be billed directly to such tendering holder.
 
    Except as provided in this Instruction 4, it will not be necessary for
transfer tax stamps to be affixed to the Notes listed in this Letter of
Transmittal.
 
5. WAIVER OF CONDITIONS.
 
    AMTROL reserves the right to waive in its reasonable judgment, in whole or
in part, any of the conditions to the Exchange Offer set forth in the
Prospectus.
 
6. MUTILATED, LOST, STOLEN OR DESTROYED NOTES.
 
    Any holder whose Notes have been mutilated, lost, stolen or destroyed,
should contact the Exchange Agent at the address indicated below for further
instructions.
 
7. REQUESTS FOR ASSISTANCE OR ADDITIONAL COPIES.
 
    Questions relating to the procedure for tendering, as well as requests for
additional copies of the Prospectus and this Letter of Transmittal, may be
directed to the Exchange Agent at the address and telephone number set forth
above. In addition, all questions relating to the Exchange Offer, as well as
requests for assistance or additional copies of the Prospectus and this Letter
of Transmittal, may be directed to AMTROL Inc. at 1400 Division Road, West
Warwick, Rhode Island 02893. Attention: Edward J. Cooney, (Telephone): (401)
884-6300.
 
    IMPORTANT: THIS LETTER OF TRANSMITTAL OR A FACSIMILE THEREOF (TOGETHER WITH
CERTIFICATES OF NOTES OR CONFIRMATION OF BOOK-ENTRY TRANSFER AND ALL OTHER
REQUIRED DOCUMENTS) OR A NOTICE OF GUARANTEED DELIVERY MUST BE RECEIVED BY THE
EXCHANGE AGENT ON OR PRIOR TO THE EXPIRATION DATE.