<PAGE>

                                                                   EXHIBIT 10.20

                           CHANGE OF CONTROL AGREEMENT

      CHANGE OF CONTROL AGREEMENT ("Agreement") by and between AMTROL INC., a
Rhode Island corporation ("AMTROL"), AMTROL Holdings Inc. ("Holdings", and
together with AMTROL, the "Company"), and Joseph DePaula (the "Executive"),
dated as of the 29th day of October, 2004.

      The Boards of Directors of AMTROL and Holdings (the "Boards") have
determined that it is in the best interests of the Company and its shareholders
to assure that the Company will have the continued service and dedication of the
Executive. In addition, the Boards believe it is imperative to diminish the
inevitable distraction of the Executive by virtue of the personal uncertainties
and risks created by a pending or threatened Change of Control and to encourage
the Executive's full attention and dedication to the Company currently and in
the event of any threatened or pending Change of Control, and to provide the
Executive with arrangements currently and upon a Change of Control which ensure
that the compensation expectations of the Executive will be satisfied and which
are competitive with those of other corporations. The Board of Directors also
believes that the autonomy, authority and responsibility possessed by the
Executive is a significant attribute of his employment and a Change of Control
would be likely to significantly diminish the attractiveness to Executive of
employment by the Company, and has determined to allow Executive to chose
whether to continue in the employ of the Company upon a Change of Control.
Therefore, in order to accomplish these objectives, the Boards have caused the
Company to enter into this Agreement.

      NOW, THEREFORE, IT IS HEREBY AGREED AS FOLLOWS:

      1. In the event either (i) Executive's employment with the Company is
terminated without Cause (as defined below) or (ii) in the event of a Change of
Control (as defined below), AMTROL will pay Executive either (a) in a single
aggregate lump sum amount or (b) in twelve (12) equal monthly installments
an aggregate amount, equal to the Executive's then current annual base salary
for a period of twelve (12) months, subject to withholdings required by law
and other applicable deductions (the aggregate amount hereinafter referred to as
the "Benefit Amount"). Additionally, Executive will be entitled to accelerated
payment of any amounts earned pursuant to the Management Incentive Compensation
Plan as described in the summary to such plan as of the date of termination of
employment or Change of Control. Executive will be entitled to the above
payments regardless of whether or not his employment with the Company continues
subsequent to a Change of Control and such payment will be in addition to any
other compensation and benefits to which the Executive is entitled as a result
of his continued employment. It is understood and agreed that provided the above
conditions are met, the Executive shall only be entitled to collect the Benefit
Amount once pursuant to this Agreement.

      For the purpose of this Agreement, a "Change of Control" shall mean:

            (i) There shall have occurred a change in control which the Company
      would be required to report in response to Item 1 of Form 8-K promulgated
      under the Securities Exchange Act of 1934, as amended (the "Exchange
      Act"), or if such

<PAGE>

      regulation is no longer in effect, any regulations promulgated by the
      Securities and Exchange Commission pursuant to the Exchange Act which are
      intended to serve similar purposes;

            (ii) The acquisition, other than from the Company, by any
      individual, entity or group (within the meaning of Section 13(d)(3) or
      14(d)(2) of the Exchange Act) of beneficial ownership (within the meaning
      of Rule 13d-3 promulgated under the Exchange Act) of 50% or more of either
      the then outstanding shares of common stock of the Company (the
      "Outstanding Company Common Stock") or the combined voting power of the
      then outstanding voting securities of the Company entitled to vote
      generally in the election of directors (the "Company Voting Securities"),
      provided, however, that any acquisition by the Company or its
      subsidiaries, or any employee benefit plan (or related trust) of the
      Company or its subsidiaries, or any corporation with respect to which,
      following such acquisition, more than 50% of, respectively, the then
      outstanding shares of common stock of such corporation and the combined
      voting power of the then outstanding voting securities of such corporation
      entitled to vote generally in the election of directors is then
      beneficially owned, directly or indirectly, by all or substantially all of
      the individuals and entities who were the beneficial owners, respectively,
      of the Outstanding Company Common Stock and Company Voting Securities
      immediately prior to such acquisition in substantially the same proportion
      as their ownership, immediately prior to such acquisition, of the
      Outstanding Company Common Stock and Company Voting Securities, as the
      case may be, shall not constitute a Change of Control; or

            (iii) Individuals who, as of January 1, 2004, constitute the Boards
      (the "Incumbent Boards") cease for any reason to constitute at least a
      majority of the Boards, provided that any individual becoming a director
      subsequent to January 1, 2004 whose election, or nomination for election
      by the Company's shareholders, was approved by a vote of at least a
      majority of the directors then comprising the Incumbent Boards shall be
      considered as though such individual were a member of the Incumbent
      Boards; or

            (iv) Approval by the stockholders of the Company of (x) a complete
      liquidation or dissolution of the Company, (y) the sale or other
      disposition of all or a material portion of the assets of the Company, or
      (z) a reorganization, merger or consolidation, in each case, with respect
      to which all or substantially all of the individuals and entities who were
      the respective beneficial owners of the Outstanding Company Common Stock
      and Company Voting Securities immediately prior to such reorganization,
      merger or consolidation do not, following such reorganization, merger or
      consolidation, beneficially own, directly or indirectly, more than 50% of,
      respectively, the then outstanding shares of common stock and the combined
      voting power of the then outstanding voting securities entitled to vote
      generally in the election of directors, as the case may be, of the
      corporation resulting from such reorganization, merger or consolidation;
      provided, however, "reorganization" for the purposes of this subsection
      1(iv)(z)

<PAGE>

      shall not include any voluntary or involuntary bankruptcy or insolvency
      filing by or against the Company.

      For purposes of this Agreement, "Cause" means:

            (i) an act or acts of personal dishonesty taken by the Executive and
      intended to result in substantial personal enrichment of the Executive at
      the expense of the Company,

            (ii) repeated violations by the Executive of the Executive's
      obligations of employment which are demonstrably willful and deliberate on
      the Executive's part and which are not remedied in a reasonable period of
      time after receipt of written notice from the Company, or

            (iii) the conviction of the Executive of a felony or a crime
      involving moral turpitude.

      2. In the event the Executive's employment is terminated at any time for
any reason, the Company agrees to provide Director's and Officer's liability
insurance for Executive for an appropriate tail period and to indemnify
Executive for any claims made against Executive as a result of his employment
with the Company.

      3. Nothing in this Change of Control Agreement alters the "at-will" nature
of Executive's Employment with the Company.

      4. The salary continuation payments discussed above are in lieu of any
other severance or salary continuation payments to which Executive may have been
entitled pursuant to Executive's offer letter dated March 6, 2001 and/or
Company policy or practice.

      5. Executive is not entitled to any salary continuation payments pursuant
to this Severance Agreement in the event Executive resigns his employment with
the Company prior to a Change of Control.

      IN WITNESS WHEREOF, the Executive has hereunto set his hand and, pursuant
to the authorization from their Boards of Directors, AMTROL and Holdings have
caused these presents to be executed in their name on their behalf, all as of
the day and year first above written.

AMTROL INC.                             AMTROL Holdings Inc.

By: /s/ Albert D. Indelicato                   By: /s/ Albert D. Indelicato
    ------------------------                       --------------------------
        Albert D. Indelicato                           Albert D. Indelicato

EXECUTIVE

    /s/ Joseph DePaula
    ------------------
        Joseph DePaula