An American apartment dweller can turn on tap water to his choice of hot, cold or in between. The resident of a flat in this east African capital knows there will be only cold water. But for the majority of Tanzania's 17 million people who live in harsh rural conditions, "the question is whether there will be water at att."

This was the illustration chosen by Tanzania's revolutionary party district secretary, Chris C. Liundi, to show that his country, Africa's prime socialist experiment "has a long way to go."

For visiting Washington mayor Marion Barry and his traveling companions, Tanzania has produced a number of lessons that District of Columbia residents might learn. It is a poor but extremely proud country.

"The philosophy here is one of people. That is, it is more important that everyone has a dime than for one to have a dollar and nine others nothing," explained mayoral aide Courtland Cox. Cox has lived and worked in Tanzania, and is a longtime admirer of Tanzanian President Julius K. Nyrere.

Barry said at the end of his first full day here that he had received a "much more rounded view" of this city and its nation than he received at stops elsewhere in Africa "because Tanzania has had a lot to do with organizing this trip."

A staff member of the U.S. International Communications Agency (formerly the USIA), which sponsored the earlier part of Barry's Africa tour, said the Tanzanian government "has taken over the entire thing [barry's visit] and turned it into an official visit," providing the mayor's party with hotel rooms and Mercedes sedans to transport them around the city.

Barry said he is not certain that assertion is accurate.

The mayor's party had one discussion after another today with Tanzanian financial institutions. The Tanzanian Investment Bank, which lends medium- and long-term money for development in the city and crops in the rural areas, emphasizes agriculture "because that is the background of the country," explained its director. The party also visited the National Bank of Commerce and the National Development Corporation.

Carter H. Dove, the Riggs National Bank vise president traveling with the mayor, was a central figure in today's discussions. Dove said that he has found "investment possibilities in all the countries we have visited and opportunities for our bank." Cox has lived and worked in Tanzania, and is a long admirer of Tanzanian President Julius K. Nyrere.

"As a result of Mayor Barry's trip, probably there is going to be some business between our bank and the countries visited," Dove said.

It was not clear whether Riggs, which has allegedly lent money to South Africa, would be permitted to invest in Tanzania, a staunch opponent of the apartheid regime.

The mayor, whenever he has been asked about Dove's presence on this trip, said that only non-Africans have so far voiced concern? Today he asked Hashim Mbita, head of the Organization of Afrian Unity's Liberation Committee, which is headquartered here. Mbita told Barry the prevailing view in Africa is that the U.S. cannot justify increased investments in South Africa in light of U.S. Human rights policies. He said Congress should legislatively "make a special case of South Africa," making investments there illegal. Companies with existing investments should use them "as a lever to bring about change."

The mayor said he appreciated the "clarifications" of Africans' views on the subject.

Barry also met with members of the Revolutionary Party and the Dar Es Salaam mayor and council, and said he came away with a much better understanding of this one-party state.

Chris Liundi, who is both the district secretary for the party and a district commissioner of the government in one section of the capital city, explained that the two are nearly always synonymous. "The government uses the language of force while the party uses the force fo language, we like to say."

He said the benefit of having one person hold both appointed positions, as is the case for local political units nationwide, is that the party gives citizens an avenue of appeal beyond the rule of government.

In an afternoon tour of a traditional African produce market that has been installed in modern facilities, Barry said he developed ideas for markets in Washington. The Kariakoo Market Corporation, a fi ve-year-old state-owned operation, controls the sales of retail produce and dry goods as well as wholesale foreign products by renting stalls to individual vendors.

Housed in a sprawling complex under a scalloped concrete roof, the market is a combination of the usual open-air African market and a shopping center.

Barry said he was struck by "the variety" of goods - vegetables, meats, fresh fish, fruits, plus plows and other hardware - sold in the tidy market place.

A similar approach might improve services of the Eastern and Farmers' produce markets in Northeast Washington as well as the newly rebuilt O Street Market of Northwest, the mayor said.