Parliament is discussing the bill, which responds to pressure for legislation to address the threat of flooding and water scarcity, during its committee stage this week.
Committee member Roger Williams tabled the code of practice amendment last week after working with the HTA.
It would introduce a procedure for phasing in water restrictions for gardeners during dry periods and prevent water companies from introducing a blanket ban.
"A phased introduction of water restrictions will ensure that consumers are not discouraged from gardening and the horticulture sector will not suffer unduly, as happened in 2006," said Williams.
The HTA is calling on members to lobby MPs on the committee to support the amendment.
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